Form One Biology
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell • Cell wall • Cell membrane • Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate• diffusion in liquids
• diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:• Osmotic pressure
• Osmotic potential
• Isotonic solution
• Hypertonic solution
• Hypotonic solution
• Turgor pressure
• Hemolysis
• Wall pressure
• Plasmolysis
• Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether• Carbon (IV) oxide is necessary for photosynthesis
• Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on• Starch
• Reducing sugars
• Non-reducing sugar
• Lipids
• Proteins
• Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on• Effect of temperature on enzymes
• Effects of enzyme concentration on the rate of a reaction
• Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beingsIntroduction To Biology
• Biology derived from Greek words - BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE
• Biology means "life knowledge"
• It is the study of living things/organisms
Branches of Biology
• Botany - study of plants
• Zoology - study of animals
• Microbiology - study' of microscopic organisms
• Morphology - study of external structure of organisms
• Anatomy - study of internal structure of organisms
• Physiology - study of the functioning or working of the cells or body
• Biochemistry - study of the chemistry of materials in living organisms
• Cytology - study of cells
• Genetics - study of inheritance
• Ecology- study of the relationship between organisms and their environment
• Taxonomy - sorting out of organisms into groups
• Histology - study of fine structure of tissues
• Virology - study of viruses
• Bacteriology - study of bacteria
• Entomology - study of insects
• Ichthyology - study of fish
Importance of Biology
• One learns about the functioning of the human body
• One understands the developmental changes that take place in the body
• It contributes immensely to improved life
• It enables one to enter careers such as:
Medicine,
Nutrition,
Public Health,
Dentistry,
Agriculture
Environmental Studies
TeachingCharacteristics of Living Things
Life defined through observations of activities carried out by living things;
Nutrition
Nutrition is the processes by which food/nutrients are acquired/made and utilized by living organisms
Green plants and certain bacteria make their own food
All other organisms feed on complex organic materialsRespiration
This is the breakdown of food to provide energy
The energy released is used for various activities in the organism• Gaseous Exchange – Process throw which respiratory gases(CO2&O2) are taken in and out through a respiratory surface
Excretion
Excretion is the removal of metabolic wastes from the body
Substances like urea, carbon dioxide (Carbon (IV) oxide)
These substances are poisonous if allowed to accumulate in the bodyGrowth and Development
Growth means irreversible change in size
All organisms increase in size that is, they grow
Development is irreversible change in complexity
As they do so, they also become differentiated in form• Reproduction-Reproduction is the formation of new individuals of a species to ensure continued existence of a species and growth of its population
Irritability
The ability of organisms to detect and respond to changes in the environmentThis is of great survival value to the organism
Movement
Is the progressive change in position from one place to another
Some organisms are sessile (ie fixed to the substratum)
The majority of plants move only certain partsCollection and Observation of Organisms Biology as a practical subject is learnt through humane handling of organisms
Materials needed for collection of organisms
• Knives to cut portions of plant stem/root or uproot
• Polythene bags to put the collected plant or specimens
• Insect collecting jars
• Insect killing jars
• Hand gloves
• Sweep nets
• Pooters
• Traps
Observation of Organisms
• Observe the plant/animal in its natural habitat before collecting
• Identify the exact place -on surface, under rock, on tree trunk, on branches
• What does it feed on?
• How does it interact with other animals and the environment?
• How many of that kind of plant or animal are in a particular place?
• Plant specimens placed on the bench and sorted out into;-
seeds/stems/roots/leaves/fruits
• Animal specimens may be left inside polythene bags if transparent
• Others (killed ones) are put in petri¬ dishes
• Use hand lens to observe the external features of small animals
Presenting the Results of Observations
• Organisms are observed and important features noted down: colour, texture ¬hard or soft; if hairy or not
Size is measured or estimated
• Biological Drawings - It is necessary to draw some of the organisms
• In making a biological drawing, magnification (enlargement) is noted
• Indicate the magnification of your drawing
• ie how many times the drawing is larger/smaller than the actual specimen MG=length of drawing/length specimen
How to Draw
How does it interact with other animals and the environment
• Several drawings of one organism may be necessary to represent all features observed, eg
• Anterior view of grasshopper shows all mouth parts properly, but not all limbs
• Lateral (side) view shows all the legs
Collection, Observation and Recording of Organisms
Collection
• Plants and animals collected from the environment, near school or within school compound using nets, bottles and gloves
• Animals collected include:-arthropods, earthworms and small vertebrates like lizards/chameleons/ rodents
• Place in polythene bags and take to the laboratory
• Stinging/poisonous insects killed using ether
• Other animals are observed live and returned to their natural habitat
• Plant specimen collected include:- leaves, flowers and whole plants
• Observations are made to show the following:-
Plants have roots, stems, leaves and flowers
Animals have legs, hair, hard outer covering, feathers, eyes, mouth, limbs and other appendages,The differences between animals and plants collected
Comparison Between Plants And Animals
Classification I Introduction• Classification is putting organisms into groups
• Classification is based on the study of external characteristics of organisms
• It involves detailed observation of structure and functions of organisms
• Organisms with similar characteristics are put in one group
• Differences in structure are used to distinguish one group from another
• The magnifying lens is an instrument that assists in the observation of fine structure eg hairs by enlarging them
Using a Magnifying Lens• A specimen is placed on the bench or held by hand,
• Then the magnifying lens is moved towards the eye until the object is dearly focused and an enlarged image is seen
The magnification can be worked out as follows:
Magnification = length of the drawing/ length of the specimen
Note: magnification has no units
Nececity/need for Classification
• To be able to identify organisms into their taxonomic groups
• To enable easier and systematic study of organisms
• To show evolutionary relationships in organisms
Major Units of Classification (Taxonomic Groups)
• Taxonomy is the study of the characteristics of organisms for the purpose of classifying them
• The groups are Taxa (singular Taxon)
The taxonomic groups include:
Species: This is the smallest unit of classification
Organisms of the same species resemble each other
The number of chromosomes in their cells is the same
Members of a species interbreed to produce fertile offspring
Genus (plural genera): A genus is made up of a number of species that share several characteristics
Members of a genus cannot interbreed and if they do, the offspring are infertile
Family: A family is made up of a number of genera that share several characteristics
Order: A number of families with common characteristics make an order
Class: Orders that share a number of characteristics make up a class
Phylum/Division: A number of classes with similar characteristics make up a phylum (plural phyla) in animals
In plants this is called a division
Kingdom: This is made up of several phyla (in animals) or divisions (in plants)
It is the largest taxonomic unit in classification
Kingdoms
Living organisms are classified into five kingdoms;
• Monera,
• Protoctista,
• Fungi,
• Plantae
• Animalia
Kingdom Fungi
• Some are unicellular while others are multicellular
• They have no chlorophyll
• Most are saprophytic eg yeasts, moulds and mushrooms
• A few are parasitic eg Puccinia graminae
Kingdom Monera (Prokaryota)
• These are very small unicellular organisms
• They lack a nuclear membrane
• do not have any bound membrane organelles
• Hence the name Prokaryota
• They are mainly bacteria, eg Vibrio cholerae
Kingdom Protoctista
• They are unicellular organisms
• Their nucleus and organelles are surrounded by membranes (eukaryotic)
• They include algae, slime moulds - fungi-like and protozoa
Kingdom Plantae
• They are all multicellular
• They contain chlorophyll and are all autotrophic
• They include; Bryophyta (mossplant), Pteridophyta (ferns) and Spermatophyta (seed bearing plants)
Kingdom Animalia
• These are all multicellular and heterotrophic
• Examples are annelida (earthworms), mollusca (snails),athropoda, chordata
• Example of Arthropods are ticks, butterflies
• Members of Chordata are fish, frogs and humans
External Features of Organisms
In plants we should look for:
• Spore capsule and rhizoids in moss plants
• Sori and fronds in ferns
• Stem, leaves, roots, flowers, fruits and seeds in plants
In animals, some important features to look for are:
• Segmentation, presence of limbs and, number of body parts, presence and number of antennae
These are found in phylum arthropoda:
• Visceral clefts, notochord, nerve tube, fur or hair, scales, fins, mammary glands, feathers and wings
• These are found in chordata
Binomial Nomenclature
• Organisms are known by their local names
• Scientists use scientific names to be able to communicate easily among themselves
• This method of naming uses two names, and is called Binomial nomenclature
• The first name is the name of the genus: (generic name) which starts with a capital letter
• The second name is the name of the species (specific name) which starts with a small letter
• The two names are underlined or written in italics
• Man belongs to the genus Homo, and the species, sapiens
• The scientific name of man is therefore Homo sapiens
• Maize belongs to the genus Zea, and the species mays
• The scientific name of maize is Zea mays
Practical Activities
• Use of Collecting Nets, Cutting Instruments and Hand Lens
• Forceps are used to collect crawling and slow moving animals
• Sweep nets are used to catch flying insects
• Cutting instrument like scapel is used to cut specimen e.g. making sections
• Hand lens is used to magnify small plants and animals
• Drawing of the magnified organism are made and the linear magnification of each calculated
Collection and Detailed Observation of Small Plants and Animals
e.g moss, ferns, bean
Look for the following:
• Moss plants: Rhizoids and spore capsules
• Fern plants: Rhizomes with adventitious roots; large leaves (fronds) with Sori (clusters of sporangia)
• Seed plants: Tree/shrub (woody) or non-woody (herbs) e.g. bean
• Root system - fibrous, adventitious and tap root
• Stem - position and length of interrnodes
• Type of leaves - simple or compound; arranged as alternate, opposite or whorled
• Flower - colour, number of parts, size and relative position of each:
• Fruits - freshy or dry; edible or not edible
• Seeds - monocotyledonous or dicotyledonous
Small animals e.g. earthworms, tick, grasshopper, butterfly, beetles
Observe these animals to see:
• Number of legs
• Presence or absence of wings
• Number of antennae
• Body covering
• Body parts
The Cell
Introduction
• The cell is the basic unit of an organism
• All living organisms are made up of cells
• Some organisms are made up of one cell and others are said to be multicellular
• Other organisms are made of many cells and are said to be multicellular
• Cells are too little to see with the naked eye
• They can only be seen with the aid of a microscope
The microscope
The microscope is used to magnify objects
Magnification
• The magnifying power is usually inscribed on the lens
• To find out how many times a specimen is magnified, the magnifying power of the objective lens is multiplied by that of the eye piece lens
• If the eye piece magnification lens is x10 and the objective lens is x4, the total magnification is x40
• Magnification has no units
• It should always have the multiplication sign
e.g.x40
Microscope parts and their functions
To View the Object
• Turn the low power objective lens until it clicks into position
• Looking through the eye piece, ensure that enough light is passing through by adjusting the mirror
• This is indicated by a bright circular area known as the field of view
• Place the slide containing the specimen on stage and clip it into position
• Make sure that the specimen is in the centre of the field of view
• Using the coarse adjustment knob, bring the low power objective lens to the lowest point
• Turn the knob gently until the specimen comes into focus
• If finer details are required, use the fine adjustment knob
• When using high power objective always move the fine adjustment knob upwards
Care of a Microscope
• Great care should be taken when handling it
• Keep it away from the edge of the bench when using it
• Always hold it with both hands when moving it in the laboratory
• Clean the lenses with special lens cleaning paper
• Make sure that the low power objective clicks in position in line with eye piece lens before and after use
• Store the microscope in a dust-proof place free of moisture
Cell Structure as Seen Through the Light Microscope
The cell as seen above has the following:
Cell membrane (Plasma membrane):
• This is a thin membrane enclosing cell contents
• It controls the movement of substances into and out of the cell
Cytoplasm:
• This is a jelly-like substance in which chemical processes are carried out
• Scattered all over the cytoplasm are small structures called organelles
• Like an animal cell, the plant cell has a cell membrane, cytoplasm and a nucleus
vacuole
• Plant cells have permanent, central vacuole
It contains cell sap where sugars and salts are stored
Cell wall:
• This is the outermost boundary of a plant cell
• It is made of cellulose
• Between the cells is a middle lamella made of calcium pectate
Chloroplasts;
• With special staining techniques it is possible to observe chloroplasts
• These are structures which contain chlorophyll, the green pigment responsible for trapping light for photosynthesis
The Electron Microscope (EM)
• Capable of magnifying up to 500,000 times
• The specimen is mounted in vacuum chamber through which an electron beam is directed
• The image is projected on to a photographic plate
• The major disadvantage of the electron microscope is that it cannot be used to observe living objects
• However, it provides a higher magnification and resolution (ability to see close points as separate) than the light microscope so that specimen can be observed in more detail
Cell Structure as Seen Through Electron Microscope
The Plasma Membrane
• Under the electron microscope, the plasma membrane is seen as a double layer
• This consists of a lipid layer sandwiched between two protein layers
• This arrangement is known as the unit membrane and the shows two lipid layers with proteins within
• Substances are transported across the membrane by active transport and diffusion
The Endoplasmic Reticulum (ER)
• This is a network of tubular structures extending throughout the cytoplasm of the cell
• It serves as a network of pathways through which materials are transported from one part of the cell to the other
• An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum
• An ER that lacks ribosomes is referred to as smooth endoplasmic reticulum
• The rough endoplasmic reticulum transports proteins while the smooth endoplasmic reticulum transports lipids
The Ribosomes
• These are small spherical structures attached to the ER
• They consist of protein and ribonucleic acid (RNA)
• They act as sites for the synthesis of proteins
Goigi Bodies
• Golgi bodies are thin, plate-like sacs arranged in stacks and distributed randomly in the cytoplasm
• Their function is packaging and transportation of glycol-proteins
• They also produce lysosomes
Mitochondria
• Each mitochondrion is a rod-shaped organelle
• Made up of a smooth outer membrane and a folded inner membrane
• The foldings of the inner membrane are called cristae
• They increase the surface area for respiration
• The inner compartments called the matrix
• Mitochondria are the sites of cellular respiration, where energy is produced
Lysosomes
• These are vesicles containing hydrolytic enzymes
• They are involved in the breakdown of micro-organisms, foreign macromolecules and damaged or worn-out cells and organelles
The Nucleus
• The nucle s is surrounded by a nuclear membrane which is a unit membrane
• The nuclear membrane has pores through which materials can move to the surrounding cytoplasm
• The nucleus contains proteins and nucleic acid deoxyribonucleic acid (DNA) and RNA
• The chromosomes are found in the nucleus
• They are the carriers of the genetic information of the cell
• The nucleolus is also located in the nucleus but it is only visible during the non-dividing phase of the cell
The Chloroplasts
• These are found only in photosynthetic cells
• Each chloroplast consists of an outer unit
membrane enclosing a series of interconnected membranes called lamellae
• At various points along their length the lamellae form stacks of disc like structures called grana
• The lamellae are embedded in a granular material called the stroma
• The chloroplasts are sites of photosynthesis
• The light reaction takes place in the lamellae while the dark reactions take place in the stroma
Comparison between animal cell and plant cell
Plant Cell Animal Cell
Cell Specialisation
Cells are specialised to perform different functions in both plants and animals
Example;
• Palisade cells have many chloroplasts for photosynthesis
• Root hair cells are long and thin to absorb water from the soil
• Red blood cells have haemoglobin which transports oxygen
• Sperm cells have a tail to swim to the egg
• Multicellular organisms cells that perform the same function are grouped together to form a tissue
• Each tissue is therefore made up of cells that are specialised to carry out a particular function
Animal Tissues- Examples of animal tissues
Plant Tissues
Organs
• An organ is made up of different tissues
• e.g the heart, lungs, kidneys and the brain in animals and roots, stems and leaves in plants
Organ systems
• Organs which work together form an organ system
• Digestive, excretory, nervous and circulatory in animals and transport and support system in plants
organism
• Different organ systems form an organism
Practical Activities
Observation and Identification of parts of a light microscope and their functions
• A light microscope is provided
• Various parts are identified and observed
• Drawing and labelling of the microscope is done
• Functions of the parts of the mircroscope are stated
• Calculations of total magnification done using the formula
• Eye piece lens maginification x objective lens maginification
Preparation and Observation of Temporary Slides of Plant Cells
• A piece of epidermis is made from the fleshy leaf of an onion bulb
It is placed on a microscope slide and a drop of water added
• A drop of iodine is added and a cover slip placed on top
• Observations are made, under low and medium power objective
• The cell wall and nucleus stain darker than other parts
• A labelled drawing is made
• The following are noted: Nucleus, cell wall, cytoplasm and cell membrane
Observation of permanent slides of animal cells
• Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells
• The slide is mounted on the microscope and observations made under low power and medium power objectives
• Labelled drawings of the cells are made
• A comparison between plant and animal cell is made
Observation and Estimation of Cell Size and Calculation of Magnification of Plant Cells
• Using the low power objective, a transparent ruler is placed on the stage of the microscope
• An estimation of the diameter of the field of view is made in millimeters
• This is converted into micrometres (1mm=1000u)
• A prepared slide of onion epidermal cells is mounted
• The cells across the centre of the field of view are counted from left and right and top to bottom
• The diameter of field of view is divided by the number of cells lying lengthwise to give an estimate of the length and width of each cell
Cell Physiology
Meaning of cell physiology
• The term physiology refers to the functions that occur in living organisms
• Cell physiology refers to the process through which substances move across the cell membrane
• Several physiological processes take place inside the cell e.g respiration
• Oxygen and glucose required enter the cell while carbon (IV) oxide and water produced leave the cell through the cell membrane
Structure and properties of cell membrane
• The cell membrane is the protective barrier that shelter cellular contents
• Movement of all substances into and out of the cells takes place across the cell membrane
• It is made up of protein and lipid molecules
• Lipid molecules have phosphate group attached to it on one end
• They are then referred to phospholipids
• The phospholipids are arranged to form a double layer
• The ends with phosphate group face outwards
• the proteins are scattered throughout the lipid double layer
• Some of these proteins act as carrier molecules that channel some material in and outside the cells
• The cell membrane allows certain molecules to pass through freely while others move through with difficulty and still others do not pass through at all
• This is selective permeability and the cell membrane is described as semi-permeable
Properties of cell membrane
Permeability
• The cell membrane is semi-permeable
• it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules
• this is due to the presence of the phospholipids double layer Polarlity
• The cell membrane has electrical charges across its surface
it has positive charged ions on the outside and negatively charged ions on the inside
this property contributes to electrical impulses sent along nerve cells
• Sensitivity to changes in temperature and pH
• Very high temperatures destroy the semi-permeability nature of the cell membrane because the proteins are denatured by extreme pH values have the same effect on the membrane permeability
• Physiological processes
• Some of the physiological processes include diffusion, osmosis and active transport
Diffusion
• Diffusion is the movement of molecules or ions from a region of high concentration to a region of low concentration aided by a concentration gradient
• diffusion continues to occur as long as there is a difference in concentration between two regions (concentration gradient)
• Stops when an equilibrium is reached i.e
, when the concentration of molecules is the same in both regions
• Diffusion is a process that occurs inside living organisms as well as the external environment
• Does not require energy
Factors Affecting Diffusion
Concentration Gradient
An increase in the concentration of molecules at one region results in a steeper concentration gradient which in turn increases the rate of diffusion
Temperature
High temperature increases kinetic energy of molecules
They move faster hence resulting in an increase in rate of diffusion, and vice versa
Size of Molecules or Ions
The smaller the size of molecules or ions, the faster their movement hence higher rate of diffusion
Density
The denser the molecules or ions diffusing, the slower the rate of diffusion, and vice versa
Medium
The medium through which diffusion occurs also affects diffusion of molecules or ions
For example, diffusion of molecules through gas and liquid media is faster than through a solid medium
Distance
This refers to the thickness or thinness of surface across which diffusion occurs
Rate of diffusion is faster when the distance is small i.e, thin surface
Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion
For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms
Role of Diffusion in Living Organisms
Some processes that depend on diffusion include the following:
• Gaseous exchange: Movement of gases through respiratory surfaces is by diffusion
• Absorption of materials into cells Cells obtain raw materials and nutrients from the surrounding tissue fluid and blood through diffusion, e.g, glucose needed for respiration diffuses from blood and tissue fluid into cells
• Excretion: Removal of metabolic waste products like carbon (IV) oxide, and ammonia out of cells is by diffusion
• Absorption of the end-products of digestion from the intestines is by diffusion
Osmosis
• Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane
• Osmosis is a special type of diffusion that involves the movement of water molecules only and not solute molecules
• Osmosis takes place in cells across the cell membrane as well as across non-living membranes
• e.g cellophane or visking tubing which are also semi-permeable
• It is purely a physical process
• Factors Affecting Osmosis
Size of solute molecules
Osmosis' occurs only when solute molecules are too large to pass through a semi-permeable membrane
Concentration Gradient
Osmosis occurs when two solutions of unequal solute concentration are separated by a semi-permeable membrane
Temperature
High temperatures increase movement of water molecules hence influence osmosis
However, too high temperatures denature proteins in cell membrane and osmosis stops
Pressure
Increase in pressure affects movement of water molecules
As pressure increases inside a plant cell, osmosis decreases
Roles of Osmosis in Living Organisms
The following processes depend on osmosis in living organisms:
• Movement of water into cells from the surrounding tissue fluid and also from cell to cell
• Absorption of water from the soil and into the roots of plants
• Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis
• Absorption of water from the alimentary canal in mammals
• Re-absorption of water in the kidney tubules
• Opening and closing stomata
Water Relations in Plant and Animal Cells
• The medium (solution) surrounding cells or organisms is described by the terms hypotonic, hypertonic and isotonic
• A solution whose solute concentration is more than that of the cell sap is said to be hypertonic
A cell placed in such a solution loses water to the surroundings by osmosis
• A solution whose solute concentration is less than that of the cell sap is said to be hypotonic
A cell placed in such a solution gains water from the surroundings by osmosis
• A solution which has the same solute concentration as the cell sap is said to be isotonic
When a cell is placed in such a solution there will be no net movement of water either into or out of the cell
Osmotic Pressure
• The term osmotic pressure describes the tendency of the solution with a high solute concentration to draw water into itself when it is separated from distilled water or dilute solution by a semi-permeable membrane
• Osmotic pressure is measured by an osmometer
• When plant cells are placed in distilled water or in a hypotonic solution, the osmotic pressure in the cells is higher than the osmotic pressure of the medium
• This causes the water to enter the cells by osmosis
• The water collects in the vacuole which increases in size
• As a result the cytoplasm is pushed outwards and it in turn presses the cell membrane next to the cell wall
• This builds up water pressure (hydrostatic pressure) inside the cell
• When the cell is stretched to the maximum, the cell wall prevents further entry of water into the cell
• Then the cell is said to be fully turgid
• The hydrostatic pressure developed is known as turgor pressure
Plasmolysis
• When a plant cell is placed in a hypertonic medium, it loses water by osmosis
• The osmotic pressure of the cell is lower than that of the medium
• The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall
• The cell becomes flaccid
The whole process is described as plasmolysis
• Incipient plasmolysis is when a cell membrane just begins to lose contact with the cell wall
• Plasmolysis can be reversed by placing the cell in distilled water or hypotonic solution
• However, full plasmolysis may not be reversed if cell stays in that state for long
Wilting
• The term wilting describes the drooping of leaves and stems of herbaceous plants after considerable amounts of water have been lost through transpiration
• It is observed in hot dry afternoons or in dry weather
• This is when the amount of water lost through transpiration exceeds the amount absorbed through the roots
• Individual cells lose turgor and become plasmolysed and the leaves and stems droop
• The condition is corrected at night when absorption of water by the roots continue while transpiration is absent
• Eventually, wilting plants may die if the soil water is not increased through rainfall or watering
Water Relations in Plants and Animals
Haemolysis
• Haemolysis is the bursting of cell membrane of red blood cells releasing their haemoglobin
• It occurs when red blood cells are placed in distilled water or hypotonic solution
• This is because the cell membrane does not resist further entry of water by osmosis after maximum water intake
Crenation
• Takes place when red blood cells are placed in hypertonic solution
• They lose water by osmosis, shrink and their shape gets distorted
• Animal cells have mechanisms that regulate their salt water balance (osmoregulation) to prevent above processes that lead to death of cells
• An Amoeba placed in distilled water, i.e
hypotonic solution, removes excess water using a contractile vacuole
• The rate of formation of contractile vacuoles increases
Active Transport
• Active transport is the movement of solutes such as
glucose, amino acids and mineral ions;
• From an area of their low concentration to an area of high concentration
• It is movement against a concentration gradient and therefore energy is required
• As such it only takes place in living organisms
• The energy needed comes from respiration
• Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins
• The shape of each type of carrier protein is specific to the type of substances conveyed through it
• It has been shown that the substance fits into a particular slot on the protein molecule,
• As the protein changes from one form of shape to another the substance is moved across and energy is expended
Factors Affecting Active Transport
Availability of oxygen
• Energy needed for active transport is provided through respiration
• An increase in the amount of oxygen results in a higher rate of respiration
• If a cell is deprived of oxygen active transport stops
Temperature
• Optimum temperature is required for respiration, hence for active transport
• Very high temperatures denature respiratory enzymes
• Very low temperatures inactivate enzymes too and active transport stops
Availability of carbohydrates
• Carbohydrates are the main substrates for respiration
• Increase in amount of carbohydrate results in more energy production during respiration and hence more active transport
• Lack of carbohydrates causes active transport to stop
Metabolic poisons
• Metabolic poisons e.g. cyanide inhibit respiration and stops active transport due to lack of energy
Role of Active Transport in Living Organisms
Processes requiring active transport:
• Absorption of mineral salts from the soil into plant roots
• Absorption of end products of digestion e.g. glucose and amino acids from the digestive tract into blood stream
• Excretion of metabolic products e.g.urea from the cells
• Re-absorption of useful substances and mineral salts back into blood capillaries from the kidney tubules
• Sodium-pump mechanism in nerve cells
• Re-absorption of useful materials from tissue fluid into the blood stream
Practical Activities
1.Experiment to Demonstrate Diffusion
• Various coloured substances such as: dyes, plant extracts and chemicals like potassium pennanganate are used
• Potassium manganate (VII) crystals are introduced to the bottom of a beaker filled with water using a glass tubing or drinking straw which is then removed
• Observations are made and the disappearance of the crystals and subsequent uniform colouring of water noted
2.Experiment to Demonstrate Osmosis Using a Visking Thbing
• A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread
• About 2 ml of 25% sucrose solution is put inside and the other end tied with thread
• The tubing is washed under running water and then blotted to dry
• It is immersed in a beaker containing distilled water and left for at least one hour or overnight
• It will then be observed that the visking tubing has greatly increased in size and has become firm
• A control experiment can be set up using distilled water inside the visking tubing in place of sucrose solution
3.xperiment to Show Osmosis using Living Tissue
• Irish potato tubers are peeled and scooped out to make hollow space at the centre
• Sucrose solution is placed inside the hollow, and the potato tuber placed in a beaker or petri-dish with distilled water
A conttrol is set using a boiled potato
• Another one using distilled water inside hollow in place of sugar solution
• The experiment is left for 3 hours to 24 hours
4.Experiment to Demonstrate Turgor and Plasmolysis in Onion Epidermal Cells
• Two strips of onion epidermis are obtained
• One is placed on a slide with distilled water while the other is placed on a slide with 25% sucrose solution and a coverslip placed on top of each
• The mounted epidermis is observed under low power microscope and then left for 30 minutes
• After 30 minutes, observations are made again
The cells in distilled water have greatly enlarged
Cells in 25% sucrose have shrunk
Nutrition in Plants and Animals
Structure of the Leaf
External Structure
• The external structure of the leaf consists of a leaf stalk or petiole and a broad leaf blade or lamina
• The lamina has a main vein midrib from which smaller veins originate
• The outline of the leaf is the margin and the tip forms the apex
Internal Structure of the Leaf
Epidermis
• This is the outer layer of cells, normally one cell thick
• It is found in both the upper and lower leaf surfaces
• The cells are arranged end to end
• The epidermis offers protection and maintains the shape of the leaf
• It is covered by a layer of cuticle which reduces evaporation
Leaf Mesophyll Consists of the palisade layer, next to upper epidermis, and the spongy layer next to the lower epidermis
Palisade Mesophyll Layer The cells are elongated and arranged close to each other leaving narrow air spaces
These contain numerous chloroplasts and are the main photosynthetic cells
In most plants, the chloroplast are distributed fairly uniformly throughout the cytoplasm
In certain plants growing in shaded habitats in dim light, most chloroplasts migrate to the upper region of the palisade cells in order to maximise absorption of the limited light available
Spongy Mesophyll Layer
• The cells are spherical in shape
• They are loosely arranged, with large intercellular spaces between them
• The spaces are air¬filled and are linked to the stomatal pores
• The spongy mesophyll cells have fewer chloroplasts than the palisade mesophyll cells
Vascular Bundles
• These are made up of the xylem and the phloem tissues
• The xylem transports water and mineral salts to the leaves
• The phloem transports food manufactured in the leaf to the other parts of the plant and from storage organs to other parts
Adaptations of Leaf for Photosynthesis
• Presence of veins with vascular bundles
Xylem vessels transport water for photosynthesis
• Phloem transports manufactured food from leaves to other parts of the plant
• Leaf lamina is thin to allow for penetration of light over short distance to reach photosynthetic cells
• Broad lamina provides a large surface area for absorption of light and carbon (IV) oxide
• Transparent cuticle and epidermal layer allow light to penetrate to mesophyll cells
• Palisade cells are close to the upper epidermis for maximum light absorption
• Presence of numerous chloroplasts in palisade mesophyll traps maximum light
• Chloroplast contain chlorophyll that traps light energy
• Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange
• Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen)
• Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light
Structure and Function of Chloroplasts
• Chloroplasts are large organelles (5 um in diameter) found in the cytoplasm of green plant cells
• They are visible under the light microscope
• They contain chlorophyll, a green pigment and other carotenoids which are yellow, orange and red in colour
• Certain plants have red or purple leaves due to abundance of these other pigments
• Chlorophyll absorbs light energy and transforms it into chemical energy
• The other pigments absorb light but only to pass it onto chlorophyll
• The wall of chloroplast consists of an outer and an inner membrane• The two make up the chloroplast envelop
• Inner membrane encloses a system of membranes called lamellae
• At intervals, the membranes form stacks of fluid filed sacs known as grana (singular granum)
• Chloroplast and other pigments are attached to the grana
• In between the lamellae is a gel-like stroma, that contains starch grains and lipid droplets
• Enzymes for the dark stage reaction (light independent stage) are embedded in the stroma
• Enzymes for the light dependent stage occur in the grana
Functions
• Absorption of light by chlorophyll and other pigments
• Light stage of photosynthesis occurs on the grana
(transformation of light energy to chemical energy
) • Carbon fixation to form carbohydrate takes place in the stroma which has enzymes for dark stage of photosynthesis
Process of Photosynthesis
• Photosynthesis involves a series of chemical reactions, all of which take place inside chloroplasts
• A general equation for photosynthesis is:
Carbon (IV)Oxide+Water light energy---Glucose+Oxygen chlorophyll
6CO2+6H2O light C6H12O+6O2chlorophyll
• The reaction occurs in two main phases or stages
• The initial state requires light and it is called the light dependent stage or simply light stage
• It takes place on the lamellae surfaces
• Its products are used in the dark stage
• The dark stage does not require light although it occurs in the light and is called light independent stage
Light-Stage
• Two reactions take place that produce raw materials for the dark stage:
• Light energy splits the water molecules into hydrogen and oxygen
• This process is called photolysis
• The hydrogen is taken up by a hydrogen acceptor called Nicotinamide adenine dinucleotide phosphate (NADP) while oxygen is released as a by-product
2H2O(l) light energy4H+O2photolysis
• Light energy strikes the chlorophyll molecules and sets in motion a series of reactions resulting in the production of a high energy molecule called adenosine triphophate (ATP)
Dark Stage
• This stage involves the fixation of carbon i.e
the reduction of carbon (IV) oxide by addition of hydrogen to form carbohydrate
• It uses the products formed during the light stage
• ATP
Carbon (IV) oxide + Hydrogen --- Carbohydrates
• The synthesis of carbohydrates does not take place in a simple straight line reaction as shown in the equation above
• It involves a series of steps that constitute what is known as the Calvin cycle
• Carbon (IV) oxide is taken up by a compound described as a carbon (IV) oxide acceptor
• This is a 5-carbon compound known as ribulose biphosphate and a six carbon compound is formed which is unstable and splits into two three-carbon compounds
• Hydrogen from the light reaction is added to the three carbon compound using energy (ATP) from the light reaction
• The result is a three carbon (triose) sugar, (phosphoglycerate or PGA)
• This is the first product of photosynthesis
• Glucose, other sugars as well as starch are made from condensation of the triose sugar molecules
• The first product is a 3-carbon sugar which condenses to form glucose (6-C sugar)
• From glucose, sucrose and eventually starch is made
• Sucrose is the form in which carbohydrate is transported from the leaves to other parts of the plant
• Starch is the storage product
• Other substances like oils and proteins are made from sugars
• This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur
Factors Influencing Photosynthesis
• Certain factors must be provided for before photosynthesis can take place
• The rate or amount of photosynthesis is also influenced by the quantity or quality of these same factors
Carbon(IV) Oxide Concentration
• Carbon (IV) oxide is one of the raw materials for photosynthesis
• No starch is formed when leaves are enclosed in an atmosphere without carbon (IV) oxide
• The concentration of carbon (IV) oxide in the atmosphere remains fairly constant at about 0.03% by volume
• However, it is possible to vary the carbon (IV) oxide concentration under experimental conditions
• Increasing the carbon (IV) oxide concentration up to 0.1 % increases the rate of photosynthesis
• Further increase reduces the rate
Light Intensity
• Light supplies the energy for photosynthesis
• Plants kept in the dark do not form starch
• Generally, increase in light intensity up to a certain optimum, increases the rate of photosynthesis
• The optimum depends on the habitat of the plant
• Plants that grow in shady places have a lower optimum than those that grow in sunny places
Water
• Water is necessary as a raw material for photosynthesis
• The amount of water available greatly affects the rate of photosynthesis
• The more water available, the more the photosynthetic rate, hence amount of food made
• Effect of water on photosynthesis can only be inferred from the yield of crops
• It is the main determinant of yield (limiting factor in the tropics)
Temperature
• The reactions involved in photosynthesis are catalysed by a series of enzymes
• A suitable temperature is therefore necessary
• The optimum temperature for photosynthesis in most plants is around 30"C
• This depends on the natural habitat of the plant
• Some plants in temperate regions have 20°C as their optimum while others in the tropics have 45°C as their optimum temperature
• The rate of photosynthesis decreases with a decrease in temperature below the optimum
• In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C
• Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation
• However, certain algae that live in hot springs e.g. Oscilatoria can photosynthesise at 75°C
Chlorophyll
• Chlorophyll traps or harnesses the energy from light
• Leaves without chlorophyll do not form starch
Chemical Compounds Which Constitute Living Organisms
• All matter is made up of chemical elements, each of which exists in the form of smaller units called atoms
• Some of the elements occur in large amounts in living things
• These include carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus
• Elements combine together to form compounds
• Some of these compounds are organic
• Organic compounds contain atoms of carbon combined with hydrogen and they are usually complex
• Other compounds are inorganic
• Most inorganic compounds do not contain carbon and hydrogen and they are usually less complex
• Cells contain hundreds of different classes of organic compounds
• However, there are four classes of organic compounds found in all cells
• These are: carbohydrates, lipids, proteins and nucleic acids
Carbohydrates
• Carbohydrates are compounds of carbon, hydrogen and oxygen
• Hydrogen and oxygen occur in the ratio of 2: 1 as in water
• Carbohydrates are classified into three main groups: monosaccharides, disaccharides and polysaccharides
Monosaccharides
• These are simple sugars
• The carbon atoms in these sugars form a chain to which hydrogen and oxygen atoms are attached
• Monosaccharides are classified according to the number of carbon atoms they possess
• The most common monosaccharides are:
Glucose - found free in fruits and vegetables
Fructose - found free in fruits and in bee honey
Galactose - found combined in milk sugar• The general formula for these monosaccharides is (CH2O)n where n is 6
• They have the same number of carbon, hydrogen and oxygen molecules i.e
C6H12O6
Properties of Monosaccharides
• They are soluble in water
• They are crystallisable
• They are sweet
• The are all reducing sugars
• This is because they reduce blue copper (II) sulphate solution when heated to copper oxide which is red in colour and insoluble
Functions of Monosaccharides
• They are oxidised in the cells to produce energy during respiration
• Formation of important biological molecules e.g. deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
• Some monosaccharides are important metabolic intermediates e.g. in photosynthesis and in respiration
• Monosaccharides are the units from which other more complex sugars are formed through condensation
Disaccharides
• These contain two monosaccharide units
• The chemical process through which a large molecule (e.g a disaccharide) is formed from smaller molecules is called condensation and it involves loss of water
Common examples of disaccharides include sucrose, maltose and lactose
• Disaccharides are broken into their monosaccharide units by heating with dilute hydrochloric acid• This is known as hydrolysis and involves addition of water molecules
• The same process takes place inside cells through enzymes
Sucrose+water_--hydrolysis-----------------glucose+fructose Properties of Disaccharides
• Sweet tasting
• Soluble in water
• Crystallisable
• Maltose and lactose are reducing sugars while sucrose is non-reducing sugar
• Sucrose is the form in which carbohydrate is transported in plants:
• This is because it is soluble andjchernically stable
• Sucrose is a storage carbohydrate in some plants e.g sugar-cane and sugar-beet
• Disaccharides are hydrolysed to produce monosaccharide units which are readily metabolised by cell to provide energy
Polysaccharides
• If many monosaccharides are joined together through condensation, a polysaccharide is formed
• Polysaccharides may consist of hundreds or even thousands of monosaccharide units
• Examples of polysaccharides:
Starch - storage material in plants
Glycogen is a storage carbohydrate in animals like starch, but has longer chains
Isulin - a storage carbohydrate in some plants e.g. Dahlia
Cellulose - structural carbohydrate in plants
Chitin - forms exoskeleton in arthropodsImportance and Functions of Polysaccharides
• They are storage carbohydrates - starch in plants glycogen in animals
• They are hydrolysed to their contituent monosaccharide units and used for respiration
• They form structural material e.g. cellulose makes cell walls
• Cellulose has wide commercial uses e.g.
Fibre in cloth industry
Cellulose is used to make paper• Carbohydrates combine with other molecules to form important structural compounds in living organisms
Examples are:
Pectins: Combine with calcium ions to form calcium pectate
Chitin: Combine with (NH) group
Makes the exoskeleton of arthropods, and walls of fungi
Lipids
• These are fats and oils
• Fats are solid at room temperature while oils are liquid
• They are made up of carbon, oxygen and hydrogen atoms
• The structural units of lipids are fatty acids and glycerol
• Fatty acids are made up of hydrocarbon chain molecules with a carboxyl group (-COOH) at one end
• In the synthesis of a lipid, three fatty acid molecules combine with one glycerol molecule to form a triglyceride
• Three molecules of water are lost in the process
• This is a condensation reaction and water is given off
• Lipids are hydrolysed e.g. during digestion to fatty acids and glycerol, water is added
condensation
Glycerol + 3 Fatty hydrolysis Lipid + Water acids
Properties
• Fats are insoluble in water but dissolve in organic solvents e.g. in alcohols
• They are chemically inactive, hence used as food storage compounds
Functions of Lipids
• Structural materials - as structural material they make up the cell membrane
• Source of energy - they are energy rich molecules
One molecule of lipid provides more energy than a carbohydrate molecule
• Storage compound - They are stored as food reserves in plants
• In animals e.g. mammals, all excess food taken is converted to fats which are stored in adipose tissue, and around internal organs such as the heart and kidneys
• Insulation - They provide insulation in animals living in cold climates
A lot of fat is stored under the skin e.g blubber in seals
• Protection - Complex lipids e.g wax on leaf surfaces protects the plant against water-loss and overheating
• Fats stored around some internal organs acts as shock absorbers, thus protecting the organs
• Source of Metabolic Water - lipids when oxidised produce metabolic water which supplements water requirements in the body
Desert animals e.g the camel accumulate large quantities of fat in the hump which when oxidised releases metabolic water
Proteins
• Proteins are the most abundant organic compounds in cells and constitute 50% of total dry weight
• Proteins are compounds which are made up of carbon, hydrogen, nitrogen, oxygen and sometimes sulphur and phosphorus
• The structural units of proteins are amino acids
• The nature of a protein is determined by the types of amino acids it is made of
• There are about 20 common amino acids that make up proteins
Essential and Non-Essential Amino Acids
• Essential amino acids are those which cannot be synthesised in the body of an organism and must therefore be provided in the diet
• There are ten amino acids which are essential for humans
• These are valine, leucine, phenylalanine, lysine, tryptophan, isoleucine, methionine, threonine, histidine and arginine
• Non-essential amino acids are those which the body can synthesise and therefore need not be available in the diet
• There are ten of them
• These are glycine, alanine, glutamic acid, aspartic acid, serine, tyrosine, proline, glutamine, arginine and cysteine
• Proteins are essential in the diet because they are not stored in the body
• Excess amino acids are deaminated
Formation of Proteins
• Proteins are made up of many amino acid units joined together through peptide bonds
• When two amino acids are joined together a dipeptide is formed
• The chemical process involved is called condensation and a molecule of water is eliminated
• When many amino acids are joined together a polypeptide chain is formed
• The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made
Functions of Proteins As structural materials proteins
Are the basic building structures of protoplasms
Proteins in conjunction with lipid form the cell membraneExamples of structural proteins include:
Keratin (in hair, nails, hoofs, feathers and wool)
Silk in spider's web
Elastin forms ligaments that join bones to each otherProtective proteins
Antibodies that protect the body against foreign antigens
Fribrogen and thrombin are involved in clot formation, preventing entry of micro-organisms when blood vessel is cutAs functional chemical compounds
Examples are hormones and enzymes that act as regulators in the body
Respiratory pigments
Examples are haemoglobin that transports oxygen in the blood and myoglobin that stores up oxygen in muscles
Contractile proteins - make up muscles, i.e myosin and actin
Proteins combine with other chemical groups to form important substances e.g. mucin in salivaSource of energy
Proteins are a source of energy in extreme conditions when carbohydrates and fats are not available e.g in starvationEnzymes
• Enzymes are biological catalysts that increase the rate of chemical reaction in the body
• They are all produced inside cells
• Some are intracellular and they catalyse reactions within the cells
• Others are extracellular and are secreted out of the cells where they work e.g. digestive enzymes
Properties of Enzymes
• Enzymes are protein in nature
• Enzymes are specific to the type of reaction they catalyse
• This is referred to as substrate specificity
• Enzymes work in very small amounts
• They remain unchanged after the reaction
• They catalyse reversible reactions
• They work very fast (high turnover numbers) e.g. the enzyme catalase works on 600 thousand molecules of hydrogen peroxide in one second
Naming of enzymes
Enzymes are named by adding the suffix -ase to:
• Name of substrate that they work on e.g.
carbohydrates - carbohydrases e.g.sucrase
Starch (amylose) - amylase
Protein - proteinase (protease)
Lipids -lipases• Type of chemical reaction catalised e.g.
Oxidation - oxidase
Reduction - reductase
Hydrolysis - hydrolaseFactors Affecting Enzyme Action
Temperature
• Enzymes are sensitive to temperature changes
• Generally, the rate of an enzyme¬controlled reaction doubles with every 10OC increase in temperature
• However, temperatures above 40°C do not favour enzyme reaction
• This is because enzymes are denatured by high temperatures
pH
• Every enzyme has a particular pH range over which it works best
• Some enzymes work best in acidic media while others function better in alkaline media
• Many enzymes function well under neutral conditions
Enzyme Concentration
• Under conditions where the substrate is in excess, the rate of an enzyme-controlled reaction increases as the enzyme concentration is increased
Substrate Concentration
• If the concentration of the substrate is increased while that of the enzyme remains constant, the rate of the reaction will increase for sometime and then become constant
• Any further increase in substrate concentration will not result in corresponding increase in the rate of the reaction
Enzyme Inhibitors
• These are substances that either compete with substrates for enzyme active sites or combine with enzymes and hence they inhibit the enzyme reaction
• e.g. certain drugs, cyanide and nerve gas
Co-factors
• Most enzymes require the presence of other compounds known as co-factors which are non-proteins
• There are three groups of co-factors
• Inorganic ions - e.g. iron, magnesium, copper and zinc
• Complex organic molecules known as prosthetic groups are attached to the enzyme e.g. flavin adenine dinucleotide (FAD) derived from vitamin B2 (riboflavin)
• Co-enzymes e.g. co¬enzyme A is involved in respiration
• All co-enzymes are derived from vitamins
Nutrition in Animals=Heterotrophism
Meaning and Types of Heterotrophism
• This is a mode of nutrition whereby organisms feed on complex organic matter from other plants or animals
• All animals are heterotrophs
• Their mode of feeding is also said to be holozoic to distinguish it from other special types of heterotrophic nutrition namely:
saprophytism
parasitism• Saprophytism/saprotrophysim- occurs in most fungi and some forms of bacteria
• Saprophytes feed on dead organic matter and cause its decomposition or decay
• Parasitism is a mode of feeding whereby one organism called the parasite feeds on or lives in another organism called the host and harms it
Modes of Feeding in Animals
• Animals have developed various structures to capture and ingest food
• The type of structures present depend on the method of feeding and the type of food
• Carnivorous animals feed on whole animals or portions of their flesh
• Herbiverous animals feed on plant material
• Omnivorous animals feed on both plants and animal materials
Feeding in Mammals
• The jaws and teeth of mammals are modified according to the type of food eaten
• Mammals have different kinds of teeth
• Each type of teeth has a particular role to play in the feeding process
Feeding in Mammals
• The jaws and teeth of mammals are modified according to the type of food eaten
• Mammals have different kinds of teeth
• Each type of teeth has a particular role to play in the feeding process
• This condition is described as heterodont
• The teeth of reptiles and amphibians are all similar in shape and carry out the same function
• They are said to be homodont
Types of Mammalian Teeth
• Mammals have four kinds of teeth
• The incisors are found at the front of the jaw
• They are sharp-edged and are used for biting
• The canines are located at the sides of the jaw
• They are pointed and are used for tearing and piercing
• The premolars are next to the canines and the molars are at the back of the jaw
• Both premolars and molars are used for crushing and grinding
• Teeth are replaced only once in a lifetime
• The first set is the milk or deciduous teeth
• These are replaced by the second set or the permanent teeth
• Dentition refers to the type of teeth, the number and their arrangement in the jaw• A dental formula shows the type and number of teeth in each half of the jaw
• The number of teeth in half of the upper jaw is represented above a line and those on the lower jaw below the line
• The first letter of each type of teeth is used in the formula i.e
i = incisors, c = canines, pm = premolars and m = molars
• The total number is obtained by multiplying by two (for the two halves of each jaw)
Adaptation of Teeth to Feeding
• In general, incisors are for cutting, canines for tearing while premolars and molars are for grinding
• However, specific modifications are observed in different mammals as an adaptation to the type of food they eat
• Teeth of Herbivores
• Incisors are long and flat with a sharp chisel¬like edge for cutting
• The enamel coating is thicker in front than at the back so that as the tooth wears out, a sharp edge is maintained
• Canines are reduced or absent
• If absent, the space left is called the diastema
• The diastema allows the tongue to hold food and push it to the grinding teeth at the back of the mouth
Premolars and molars:
• These are transversely ridged
• The ridges on the upper teeth fit into grooves on the lower ones
• This gives a sideways grinding surface
• The teeth of herbivores have open roots i.e
, wide opening into the pulp cavity
• This ensures a continued adequate supply of food and oxygen to the tooth
• In some herbivores, such as rabbits and elephants, the incisors continue to grow throughout life
Teeth of Carnivores
• Incisors are reduced in size and pointed
• They are well suited for grasping food and holding prey
• Canines are long, pointed and curved
• They are used for piercing and tearing flesh as well as for attack and defence
Premolars and molars: In general, they are long and longitudinally ridged to increase surface area for crushing
Carnassial Teeth: These are the last premolars on the upper jaw and the first molars on the lower one
• They are enlarged for cutting flesh
• They act as a pair of shears
• They also crush bones
• The teeth of carnivores have closed roots i.e
, only a very small opening of the pulp cavity to allow food and oxygen to keep teeth alive
• Once broken, no re-growth can take place
Teeth of Omnivores
• Incisors have a wide surface for cutting
• Canines are bluntly pointed for tearing
• Premolars and molars have cusps for crushing and grinding
• The premolars have two blunt cusps while the molars have three to four
Internal Structure of tooth
The tooth consists of two main parts:Crown: The portion above the gum; it is covered by the enamel
Root: The portion below the gum; it is covered by the cement
• The tooth has two roots
Neck: Is the region at the same level with the gum
• It forms the junction between the crown and the root
• It is covered by enamel
Incisors and canines have one root only
• Premolars have one or two roots while molars have two to three roots each
• Internally, the bulk of the tooth is made up of dentine which consists of living cells and extends to the root
• It is composed of calcium salts, collagen and water
• It is harder than bone but wears out with use
• This is why it is covered by enamel which is the hardest substance in a mammal's body
Pulp Cavity: Contains blood vessels which provide nutrients to the dentine and remove waste products
• It also contains nerve endings which detect heat, cold and pain
Cement: Fixes the tooth firmly to the jaw bone
Common Dental Diseases
Dental Carries
• Dental carries are the holes or cavities that are formed as acid corrodes enamel and eventually the dentine
Causes
This is caused by bacteria acting on the food left between teeth and on the cusp
Acids are formed that eventually corrode the enamel
The pulp cavity is eventually reached
A lot of pain is experienced then
The bacteria then infect the pulp cavity and the whole tooth decaysTreatment
Treatment depends on the extent of the dental caries:
Extraction of Tooth
Filling - this involves replacing the dentine with amalgam, a mixture of hard elements e.g silver and tin
Root Canal Treatment - This involves surgery and reconstruction
It saves severely damaged teeth
The nerves in the root canal are surgically severed
The tooth is cleaned and filled up with amalgamPeriodontal Diseases
• These are diseases of the gum
• The gum becomes inflamed, and starts bleeding
• Progression of the disease leads to infection of the fibres in the periodontal membranes and the tooth becomes loose
• This condition is known as pyorrhoea
• The diseases are caused by poor cleaning of the teeth
• The accumulation of food particles leading to formation of plaque, lack of adequate vitamin A and C in the diet
Treatment
• Nutrition - by taking adequate balanced diet rich in vitamins A and C
• Antibiotics are used to kill bacteria
• Anti-inflamatory drugs are given
• Antiseptic is prescribed to use in cleaning the mouth daily to prevent further proliferation of bacteria
• The plaque is removed-drilled away - a procedure known as scaling
Care of Teeth
In order to maintain healthy teeth the following points should be observed:
• A proper diet that includes calcium and vitamins, particularly vitamin D is essential
• The diet should also contain very small quantities of fluorine to strengthen the enamel
• Large quantities of fluorine are harmful
• The enamel becomes brown, a condition known as dental flourosis
• Chewing of hard fibrous foods like carrots and sugar cane to strengthen and cleanse the teeth
• Proper use of teeth e.g. not using teeth to open bottles and cut thread
• Regular and thorough brushing of teeth after meals
• Dental floss can be used to clean between the teeth
• Not eating sweets and sugary foods between meals
• Regular visits to the dentist for check¬up
• Washing the mouth with strong salt solution or with any other mouth wash with antiseptic properties
Digestive System and Digestion in Humans
• Organs that are involved with feeding in humans constitute the digestive system
Digestive System and Associated Glands
• Human digestive system starts at the mouth and ends at the anus
• This is the alimentary canal
• Digestion takes place inside the lumen of the alimentary canal
• The epithelial wall that faces the lumen has mucus glands (goblet cells)
• These secrete mucus that lubricate food and prevent the wall from being digested by digestive enzymes
• Present at specific regions are glands that secrete digestive enzymes
• The liver and pancreas are organs that are closely associated with the alimentary canal
• Their secretions get into the lumen and assist in digestions
Digestive system consists of:
• Mouth
• Oesophagus
• Stomach
Small intestines
- consist of duodenum, the first part next to the stomach, ileum - the last part that ends up in a vestigial caecum and appendix which are non¬functional
Large intestines
consist of: colon and rectum that ends in the anus
Ingestion, Digestion and Absorption
• Feeding in humans involves the following processes:
• Ingestion: This is the introduction of the food into the mouth
• Digestion: This is the mechanical and chemical breakdown of the food into simpler, soluble and absorbable units
• Absorption: Taking into blood the digested products
• Assimilation: Use of food in body cells
• Mechanical breakdown of the food takes place with the help of the teeth
• Chemical digestion involves enzymes
Digestion in the Mouth
• In the mouth, both mechanical and chemical digestion takes place
• Food is mixed with saliva and is broken into smaller particles by the action of teeth
• Saliva contains the enzyme amylase
• It also contains water and mucus which lubricate and soften food in order to make swallowing easy
• Saliva is slightly alkaline and thus provides a suitable pH for amylase to act on cooked starch, changing it to maltose
• The food is then swallowed in the form of semisolid balls known as boluses
• Each bolus moves down the oesophagus by a process known as peristalsis
• Circular and longitudinal muscles along the wall of the alimentary canal contract and relax pushing the food along
Digestion in the Stomach
• In the stomach, the food is mixed with gastric juice secreted by gastric glands in the stomach wall
• Gastric juice contains pepsin, rennin and hydrochloric acid
• The acid provides a low pH of 1.5-2.0 suitable for the action of pepsin
• Pepsin breaks down protein into peptides
• Rennin coagulates the milk protein casein
• The stomach wall has strong circular and longitudinal muscles whose contraction mixes the food with digestive juices in the stomach
Digestion in the Duodenum
• In the duodenum the food is mixed with bile and pancreatic juice
• Bile contains bile salts and bile pigments
• The salts emulsify fats, thus providing a large surface area for action of lipase
• Pancreatic juice contains three enzymes:
Trypsin which breaks down proteins into peptides and amino acids,
Amylase which breaks down starch into maltose, and
Lipase which breaks down lipids into fatty acids and glycerol• These enzymes act best in an alkaline medium which is provided for by the bile
Digestion in ileum
• Epithelial cells in ileum secrete intestinal juice, also known as succus entericus
• This contains enzymes which complete the digestion of protein into amino acids, carbohydrates into monosaccharides and lipids into fatty acids and glycerol
Absorption
• This is the diffusion of the products of digestion into the blood of the animal
• It takes place mainly in the small intestines though alcohol and some glucose are absorbed in the stomach
The ileum is adapted for absorption in the following ways:
• It is highly coiled
• The coiling ensures that food moves along slowly to allow time for its digestion and absorption
• It is long to provide a large surface area for absorption
• The epithelium has many finger-like projections called villi (singular villus)
• They greatly increase the surface area for absorption
• Villi have microvilli that further increase the surface area for absorption
• The wall of villi has thin epithelial lining to facilitate fast diffusion of products of digestion
• Has numerous blood vessels for transport of the end products of digestion
• Has lacteal vessels; for absorption of fatty acids and glycerol and transport of lipids
Absorption of Glucose and Amino Acids
• Glucose and other monosaccharides as well as amino acids are absorbed through the villi epithelium and directly into the blood capillaries
• First they are carried to the liver through the hepatic portal vein, then taken to all organs via circulatory system
Absorption of Fatty Acids and Glycerol
• Fatty acids and glycerol diffuse through the epithelial cells of villi and into the lacteal
• When inside the villi epithelial cells, the fatty acids combine with glycerol to make tiny fat droplets which give the lacteal a milky appearance
• The lacteals join the main lymph vessel that empties its contents into the bloodstream in the thoracic region
• Once inside the blood, the lipid droplets are hydrolysed to fatty acids and glycerol
Absorption of Vitamins and Mineral Salts
• Vitamins and mineral salts are absorbed into the blood capillaries in' the villi
Water is mainly absorbed in the colon
• As a result the undigested food is in a semi-solid form (faeces) when it reaches the rectum
Egestion: This is removal of undigested or indigestible material from the body
Faeces are temporarily stored in the rectum then voided through the anus
Opening of the anus is controlled by sphincter muscles
Assimilation: This is the incorporation of the food into the cells where it is used for various chemical processes
Carbohydrates
• used to provide energy for the body
• Excess glucose is converted to glycogen and stored in the liver and muscles
• Some of the excess carbohydrates are also converted into fat in the liver and stored in the adipose tissue' (fat storage tissue), in the mesenteries and in the connective tissue under the skin, around the heart and other internal organs
Proteins
• Amino acids are used to build new cells and repair worn out ones
• They are also used for the synthesis of protein compounds
• Excess amino acids are de-aminated in the liver
• Urea is formed from the nitrogen part
• The remaining carbohydrate portion is used for energy or it is converted to glycogen or fat and stored
Lipids
• Fats are primarily stored in the fat storage tissues
• When carbohydrates intake is low in the body, fats are oxidised to provide energy
• They are also used as structural materials e.g. phospholipids in cell membrane
They act as cushion, protecting delicate organs like the heart
• Stored fats under the skin act as heat insulators
Summary of digestion in humans
Importance of Vitamins, Mineral Salts, Roughage and Water in Human Nutrition Vitamins• These are organic compounds that are essential for proper growth, development and functioning of the body
• Vitamins are required in very small quantities
• They are not stored and must be included in the diet
• Vitamins Band C are soluble in water, the rest are soluble in fat
• Various vitamins are used in different ways
Mineral Salts
• Mineral ions are needed in the human body
• Some are needed in small amounts while others are needed in very small amounts (trace)
• All are vital to human health
• Nevertheless, their absence results in noticeable mulfunction of the body processes
Water
• Water is a constituent of blood and intercellular fluid
• It is also a constituent of cytoplasm
• Water makes up to 60-70% of total fresh weight in humans
• No life can exist without water
Functions of Water
• Acts as a medium in which chemical reactions in the body takes place
• Acts as a solvent and it is used to transport materials within the body
• Acts as a coolant due to its high latent heat of vaporisation
• Hence, evaporation of sweat lowers body temperature
• Takes part in chemical reactions i.e
hydrolysis
Vitamins, sources, uses and the deficiency disease resulting from their absence in diet
Functions of Water• Acts as a medium in which chemical reactions in the body takes place
• Acts as a solvent and it is used to transport materials within the body
• Acts as a coolant due to its high latent heat of vaporisation
Hence, evaporation of sweat lowers body temperature
• Takes part in chemical reactions ie hydrolysis
Vitamins, sources, uses and the deficiency disease resulting from their absence in diet
Roughage• Roughage is dietary fibre and it consists mainly of cellulose
• It adds bulk to the food and provides grip for the gut muscles to enhance peristalsis
• Roughage does not provide any nutritional value because humans and all animals not produce cellulase enzyme to digest cellulose
• In herbivores symbiotic bacteria in the gut produce cellulase that digests cellulose
Factors Determining Energy Requirements in Humans
• Age: Infants, for instance, need a greater proportion of protein than adults
• Sex: males generally require more carbohydrates than females
• The requirements of specific nutrients for females depends on the stage of development in the life cycle
• Adolescent girls require more iron in their diet; expectant and nursing mothers require a lot of proteins and mineral salts
• State of Health: A sick individual requires more of certain nutrients eg proteins, than a healthy one
• Occupation: An office worker needs less nutrients than a manual worker
Balanced Diet
• A diet is balanced when it contains all the body's nutrient requirements and in the right amounts or proportions
A balanced diet should contain the following:
• Carbohydrates
• Proteins
• Lipids
• Vitamins
• Mineral Salts
• Water
• Dietary fibre or roughage
Malnutrition
• This is faulty or bad feeding where the intake of either less or more than the required amount of food or total lack of some food components
Deficiency Diseases
• Deficiency diseases result from prolonged absence of certain components in the diet
- Examples are:
Marasmus
• Lack of enough food reuslts in thin arms and legs,
severe loss of fluid,
general body wasting
sunken eyesKwashiorkor
Lack of protein in the diet of children
The symptoms of kwashiorkor include wasting of the body, red thin hair, swollen abdomen and scaly skin• Other deficiency diseases are due to lack of accessory food factors (vitamins and mineral salts)
Such diseases include rickets, goitre and anaemia
• Treatment of these deficiency diseases is by supplying the patient with the component missing in the diet
The End
Practical Activities
• Experiments to show that Carbon (IV) Oxide is necessary for Photosynthesis
• Experiment to Show Effect of Light on Photosynthesis
• Experiment to Show the Effect of Chlorophyll on Photosynthesis
• Experiment To Observe Stomata Distribution in Different Leaves
• Test for Reducing Sugar
• Test for non-reducing sugar
• Test for Lipids;
(a) Grease Spot Test
(b) Emulsion Test
• Test for Proteins -Biuret Test
• Experiment To Investigate Presence of Enzyme in Living Tissue
• Dissection of a Rabbit to show the Digestive System.
Form Two Biology
By the end of form two work, the learner should be able to:
Define the term transport
List substances transported in plants and animals
Link surface area to volume ratio of organisms to the transport system of the organism
Explain the necessity of transport in plants
Draw the structure of roots and root hairs
Relate the structure of the root to their functions
Observe prepared slides of roots and root hairs
Compare monocotyledons and dicotyledonous root sections
Observe charts and drawings of root sections
Draw and label the structure of the Xylem Vessel
Define Xylem Vessel
Relate the structure of the Xylem Vessel to its function
Define Tracheid elements
Relate the structure of the Tracheid elements to their functions
Distinguish between xylem vessels and Tracheid elements
Describe water and salt uptake by roots from the soil
Explain the physiological process involved in the uptake of water and mineral salts
Draw the monocotyledonous and dicotyledonous stem sections
Define the term transpiration and relate the structure of xylem to its role in transpiration
Draw and label the internal and the external structure of a leaf
Describe the functions of the leaf
Relate the parts of a leaf to their functions
Demonstrate the movement of water in plants
Observe prepared leaf sections to identify vascular tissues
Discuss the forces involved in movement of water in plants such as transpiration, pull, cohesion and adhesion capillarity and root pressures
Demonstrate the forces involved in movement of water in plants
Identify the importance of transpiration in plants
Discuss the importance of transpiration in plants
Explain what the phloem is
Draw the structure of the phloem and relate its structure to its function
List down materials translocated in the phloem
Draw the structure of the phloem
Relate the parts of the phloem to its functions
Discuss the function of the phloem
List down materials translocated and the sites of storage in the phloem
Set up an experiment to investigate translocation of food substances in dicotyledonous plants
Set up an experiment to investigate translocation of food substances in a monocotyledonous plant
Explain the processes involved in the translocation of food in plants Identify unicellular organisms such as amoeba
Describe transport of substances in unicellular organisms
Explain the necessity of an elaborate transport system in most animals
Define an open circulatory system
Discuss the open circulatory system
Draw the open circulatory system of an insect
Define an closed transport system
Identify animals with the open circulatory system
Distinguish between closed and open circulatory systems
Define an Double circulatory system
Draw and label circulatory systems in mammals
Dissect a rabbit and observe its transport system
Draw and label the external parts of the mammalian heart
Draw and label the internal structure of the mammalian heart
Explain the functions of the heart
Relate the structure of the heart to its functions
Trace the path taken by blood from the heart to the body parts and back to the heart
State the substances supported by the blood of mammals
Describe the flow of oxygenated blood in and out of the body through the heart
Explain the structure of arteries, veins and capillaries
Relate the structure of the arteries, veins and capillaries to their function
Name the common diseases of circulatory system such as thrombosis, varicose veins
Suggest methods of control/prevention for the diseases.
List the components of the blood
State the functions of each of the blood components
Explain how oxygen and carbon dioxide are transported in the blood
Describe the mechanisms of blood clotting and its importance
Describe the human blood group system
State the importance of blood groups in blood transfusion
Discuss the rhesus factor
State the role of the rhesus factor in blood transfusion
Examine the external and internal structure of a cows heart
Investigate pulse rate at the wrist
Defining immunity
Describe immune response
Differentiate between natural and artificial immunity
Define vaccination
Describe importance of vaccination against diseases such as tuberculosis, poliomyelitis, measles, diphtheria, whooping cough
Define allergic reactions and explain their causes
Carry out an experiment to demonstrate the unidirectional flow of blood in the cutaneous veins of the forearm
Define gaseous exchange
Identify the gases that are exchanged in the living organism
Explain the importance of gaseous exchange in organisms
Describe the stomata
Draw and label open and closed stomata
Explain stomata and gaseous exchange
Investigate the presence of stomata on leaves
Investigate the shape of guard cells and the distribution of stomata on leaves
Explain the mechanism of opening and closing of stomata
Describe photosynthetic/glucose accumulation theory of opening and closing stomata
Describe inter-conversion of starch and glucose and ion accumulation theories
Investigate the internal structure of stems and leaf stalk in aerial and aquatic plants
Investigate tissue distribution in aerial leaves and stems
describe Cuticular and lenticular gaseous exchange
Draw the structure of the root
Describe how gaseous exchange takes place through the epidermis of the roots
Examine various types of gaseous exchange structure in different organisms
Relate the various types of gaseous exchange structure to their functions in different organisms
State the characteristics of gaseous exchange surfaces in different organisms
Examine the gaseous exchange structures of a grasshopper or a locust
Draw the gaseous exchange structure of an insect
Draw and label the structure of gaseous exchange in bony fish
Relate the gills to their function
describe the mechanism of gaseous exchange in bony fish
Examine the location and number of gills in gill chambers of bony fish
Examine, draw and label the gill of a bony fish
describe the gaseous exchange I a frog through its gills, skin, mouth and lungs.
State the structure involved in gaseous exchange in human beings
Explain the features of the structures involved in gaseous exchange in human beings
Draw and label the structures involved in gaseous exchange in human beings
Examine a dissected mammal to locate the gaseous exchange structures
Describe the mechanism of breathing in human beings
Draw and label the alveoli where gaseous exchange occur in human beings
Describe how gaseous exchange occurs in alveoli
Explain how human beings are adapted to their functions
Able to examine the mammalian lung
Demonstrate the breathing mechanism of the lungs and diaphragm in a model thoracic cavity
Demonstrate the breathing movement of ribs and muscles by using a model
Examine the factors affecting the rate of breathing in human beings
Explain the factors which control the rate of breathing in human beings
State the causes of respiratory diseases
Discuss the symptoms of respiratory disease
explain the prevention measures of respiratory diseases
demonstrate the effect of exercise on the rate of breathing
Define respiration
State the significance of respiration
Draw and label mitochondria
Define Anaerobic respiration
Describe Anaerobic respiration in plants
Describe Anaerobic respiration in animals
Identify the gas given off when food is burnt
Investigate the gas produced during fermentation
State the economic importance of anaerobic respiration
Discuss the economic importance of anaerobic respiration in both plants and animals
Explain anaerobic respiration
Distinguish between anaerobic and aerobic respiration
Compare energy production in anaerobic and aerobic respiration
Investigate the production of heat by germinating seeds
Demonstrate that respiration takes place in plants
Show aerobic respiration in animals
Show the aerobic respiration takes place in animals
Define terms stated
Distinguish between excretion and egestion
Explain the necessity of excretion in plants and animals
Describe the methods of excretion in plants
List down useful and harmful excretory products in plants
Identify the uses of excretory products in plants
Describe the uses of excretory products in plants
Describe excretion and homeostasis in unicellular animals such as amoeba
Draw an amoeba
Describe excretion in fresh water amoeba
Explain the need for complex animals for excretion
List down organs involved In excretion in animals
List down waste products released by various organs
Examine the kidney of a mammal
Draw and label the external structure of a kidney
Make a vertical section through the kidney
Identify the internal parts of the kidney
Draw and label parts of the nephron
Relate its structure to its role in urine formation
Identify the hormones involved in Neuro-endoctrine system and homeostasis eg insulin
Explain the process of urine formation in the kidney
Describe the role of various hormones in urine formation
Describe the components and role of Neuro-endoctrine systems
Distinguish between internal and external environments
Explain the general working of the homeostatic mechanism
Define osmoregulation
Describe the role of the kidney in osmoregulation
Explain the role of hypothalamus in osmoregulation
Explain Diabetes insipidus and other common kidney diseases
Describe the causes of Diabetes insipidus and other common kidney diseases
State possible control/prevention methods of Diabetes insipidus
Draw and label parts of the skin
Relate the parts of the skin to their functions
Distinguish between osmoregulation and thermoregulation
Describe the role of the skin in osmoregulation
Describe the role of the skin in thermoregulation
Identify behavioral and physiological means of thermoregulation in animals
Describe behavioral and physiological means of thermoregulation in animals
Explain Heat loss and heat gain
Describe the various methods of Heat loss and heat gain in mammals
Explain the terms Surface area to volume ratio in relation
Relate the body size of mammals to heat loss and heat gain
Draw and label the liver and its associated parts
Describe the liver and its role in homeostasis
List down some of the functions of the liver
Describe the functions of the liver
Identify all the diseases of the liver
Describe the symptoms and possible control of diabetes mellitus and other liver diseases
Explain the causes symptoms and diseases of the liver
explain catalase enzyme and hydrogen peroxide
describe the role of catalase enzyme in breaking down hydrogen peroxide,,use liver and kidney to investigate the reaction
Describe the role of the liver in blood sugar control
Describe the role of insulin hormone
Explain the regulation of blood sugar
Describe a flow chart showing the regulation of blood sugar
Describe temperature regulation in other animals
Relate parts of the lungs to its functions
Draw and label parts of the lungs
describe the functions of the lungs as discussed during gaseous exchange
Identify a mammals lungs
Observe and describe structures of lungs in relation to functionsTransport in Plants and Animals.Introduction
Transport is the movement of substances within an organism.
All living cells require oxygen and food for various metabolic processes.
These substances must be transported to the cells.
Metabolic processes in the cells produce excretory products which should be eliminated before they accumulate.
The excretory products should be transported to sites of excretion.
Organisms like amoeba are unicellular.
They have a large surface area to volume ratio.
The body is in contact with the environment.
Diffusion is adequate to transport substances across the cell membrane and within the organism.
Large multi-cellular organisms have complex structure where cells are far from each other hence diffusion alone cannot meet the demand for supply and removal of substances.
Therefore an elaborate transport system is necessary.Transport in plants
Simple plants such as mosses and liverworts lack specialized transport system.
Higher plants have specialized transport systems known as the vascular bundle.
Xylem transports water and mineral salts .
Phloem transports dissolved food substances like sugars.Internal structure of roots and root hairs
The main functions of roots are ;
Anchorage
absorption.
storage
gaseous exchange.
The outermost layer in a root is the piliferous layer.
This is a special epidermis of young roots whose cells give rise to root hairs.
Root hairs are microscopic outgrowths of epidermal cells.
They are found just behind the root tip,
They are one cell thick for efficient absorption of substances.
They are numerous and elongated providing a large surface area for absorption of water and mineral salts.
Root hairs penetrate the soil and make close contact with it.
Below the piliferous layer is the cortex.
This is made up of loosely packed, thin walled parenchyma cells.
Water molecules pass through this tissue to reach the vascuiar bundles.
In some young plant stems, cortex cells contain chloroplasts.
The endodermis (starch sheath) is a single layer of cells with starch grains.
The endodermis has a casparian strip which has an impervious deposit controlling the entry of water and mineral salts into xylem vessels.
Pericyc1e forms a layer next to the endodermis.
Next to the pericycle is the vascular tissue.
In the Dicotyledonous root, xylem forms a star shape in the centre, with phloem in between the arms.
It has no pith. In monocotyledonous root, xylem alternates with phloem and there is a pith in the centre.Internal structure of a root hair cell
The Stem
The main functions of the stem are;
support and exposure of leaves and flowers to the environment,
conducting water and mineral salts
conducting manufactured food from leaves to other parts of the plant.
In monocotyledonous stems, vascular bundles are scattered all over the stem, while in dicotyledonous stems vascular bundles are arranged in a ring.
Vascular bundles are continuous from root to stems and leaves.
The epidermis forms a single layer of cells enclosing other tissues.
The outer walls of the cells have waxy cuticle to prevent excessive loss of water.
The cortex is a layer next to the epidermis.
It has collenchyma, parenchyma and schlerenchyma cells.Collenchyma
Is next to the epidermis and has thickened walls at the corners which strengthen the stem.Parenchyma
Cells are irregular in shape, thin walled and loosely arranged hence creating intercellular spaces filled with air.
They are packing tissues and food storage areas. Sclerenchyma
Cells are closely connected to vascular bundles.
These cells are thickened by deposition of lignin and they provide support to plants. Pith
Is the central region having parenchyma cells.Absorption of Water and Mineral Salts Absorption of Water
Root hair cell has solutes in the vacuole and hence a higher osmotic pressure than the surrounding soil water solution.
Water moves into the root hair cells by osmosis along a concentration gradient.
This makes the sap in the root hair cell to have a lower osmotic pressure than the surrounding cells.
Therefore water moves from root hair cells into the surrounding cortex cells by osmosis.
The process continues until the water gets into the xylem vessels .Uptake of Mineral Salts
If the concentration of mineral salts in solution is greater than its concentration in root hair cell, the mineral salts enter the root hair cell by diffusion.
If the concentration of mineral salts in the root hair cells is greater than in the soil water, the mineral salts enter the root hairs by active transport.
Most minerals are absorbed in this way.
Mineral salts move from cell to cell by active transport until they reach the xylem vessel.
Once inside the xylem vessels, mineral salts are transported in solution as the water moves up due to root pressure, capillary attraction and cohesion and adhesion forces.Transpiration
Transpiration is the process by which plants lose water in the form of water vapour into the atmosphere.
Water is lost through stomata, cuticle and lenticels.
Stomatal transpiration:
This accounts for 80-90% of the total transpiration in plants.
Stomata are found on the leaves.Cuticular transpiration:
The cuticle is found on the leaves, and a little water is lost through it.
Plants with thick cuticles do not lose water through the cuticle.Lenticular transpiration
Is loss' of water through lenticels.
These are found on stems of woody plants.
Water lost through the stomata and cuticle by evaporation leads to evaporation of water from surfaces of mesophyll cells .
The mesophyll cells draw water from the xylem vessels by osmosis.
The xylem in the leaf is continuous with xy lem in the stem and root.Structure and function of Xylem
Movement of water is through the xylem.
Xylem tissue is made up of vessels and tracheids.Xylem Vessels
Xylem vessels are formed from cells that are elongated along the vertical axis and arranged end to end.
During development, the cross walls and organelles disappear and a continuous tube is formed.
The cells are dead and their walls are strengthened by deposition of lignin.
The lignin has been deposited in various ways.
This results in different types of thickening
Annular.
Simple spiral.
Double spiral.
Reticulate.The bordered pits are areas without lignin on xylem vessels and allow passage of water in and out of the lumen to neighbouring cells.
Tracheids
Tracheids have cross-walls that are perforated.
Their walls are deposited with lignin.
Unlike the xylem vessels, their end walls are tapering or chisel-shaped.
Their lumen is narrower.
Besides transport of water, xylem has another function of strengthening the plant which is provided by xylem fibres and xylem parenchyma.Xylem fibres ;
Are cells that are strengthened with lignin.
They form wood.Xylem parenchyma:
These are cells found between vessels.
They form the packing tissue.Forces involved in Transportation of Water and Mineral Salts
Transpiration pull
As water vaporises from spongy mesophyll cells into sub-stomatal air spaces, the cell sap of mesophyll cells develop a higher osmotic pressure than adjacent cells.
Water is then drawn into mesophyll cells by osmosis from adjacent cells and finally from xylem vessels.
A force is created in the leaves which pulls water from xylem vessels in the stem and root.
This force is called transpiration pull .Cohesion and Adhesion:
The attraction between water molecules is called cohesion.
The attraction between water molecules and the walls of xylem vessels is called adhesion.
The forces of cohesion and adhesion maintain a continuous flow of water in the xylem from the root to the leaves.Capillarity:
Is the ability of water to rise in fine capillary tubes due to surface tension.
Xylem vessels are narrow, so water moves through them by capillarity.Root Pressure:
If the stem of a plant is cut above the ground level, it is observed that cell sap continues to come out of the cut surface.
This shows that there is a force in the roots that pushes water up to the stem.
This force is known as root pressure.Importance of Transpiration
Transpiration leads to excessive loss of water if unchecked.Some beneficial effects are:
Replacement of water lost during the process.
Movement of water up the plant is by continuous absorption of water from the soil.
Mineral salts are transported up the plant.
Transpiration ensures cooling of the plant in hot weather.
Excessive loss of water leads to wilting' and eventually death if water is not available in the soil.Factors Affecting Transpiration The factors that affect transpiration are grouped into two.
i.e. environmental and structural.Environmental factors
Temperature
High temperature increases the internal temperature of the leaf .
which in turn increases kinetic energy of water molecules which increases evaporation.
High temperatures dry the air around the leaf surface maintaining a high concentration gradient.
More water vapour is therefore lost from the leaf to the air.Humidity
The higher the humidity of the air around the leaf, the lower the rate of transpiration.
The humidity difference between the inside of the leaf and the outside is called the saturation deficit.
In dry atmosphere, the saturation deficit is high.
At such times, transpiration rate is high.Wind
Wind carries away water vapour as fast as it diffuses out of the leaves.
This prevents the air around the leaves from becoming saturated with vapour.
On a windy day, the rate of transpiration is high.Light Intensity
When light intensity is high; more stomata open hence high rate of transpiration.Atmospheric Pressure
The lower the atmospheric pressure the higher the kinetic energy of water molecules hence more evaporation.
Most of the plants at higher altitudes where atmospheric pressure is very low have adaptations to prevent excessive water-loss.Availability of Water
The more water there is in the soil, the more is absorbed by the plant and hence a lot of water is lost by transpiration.Structural Factors Cuticle
Plants growing in arid or semi-arid areas have leaves covered with a thick waxy cuticle.Stomata
The more the stomata, the higher the rate of transpiration.
Xerophytes have few stomata which reduce water-loss.
Some have sunken stomata which reduces the rate of transpiration as the water vapour accumulates in the pits.
Others have stomata on the lower leaf surface hence reducing the rate of water-loss.
Some plants have reversed stomatal rhythm whereby stomata close during the day and open at night.
This helps to reduce water-loss.Leaf size and shape
Plants in wet areas have large surface area for transpiration.
Xerophytes have small narrow leaves to reduce water-loss.
The photometer can be used to determine transpiration in different environmental conditions.Translocation of organic compounds
Translocation of soluble organic products of photosynthesis within a plant is called translocation.
It occurs in phloem in sieve tubes.
Substances translocated include glucose, amino acids, vitamins.
These are translocated to the growing regions like stem, root apex, storage organs e.g. corms, bulbs and secretory organs such as nectar glands.Phloem
phloem is made up of;
sieve tubes,
companion cells
parenchyma, a packing tissue
schlerenchyma, a strengthening tissue Sieve Tubes
These are elongated cells arranged end to end along the vertical axis.
The cross walls are perforated by many pores to make a sieve plate.
Most organelles disappear and those that remain are pushed to the sides of the sieve tube.
Cytoplasmic strands pass through the pores in the plate into adjacent cells.
Food substances are translocated through cytoplasmic strands.Companion Cells
Companion cells are small cells with large nuclei and many mitochondria.
They are found alongside each sieve element.
The companion cell is connected to the tube through plasmodesmata.
The mitochondria generate energy required for translocation. Phloem Parenchyma
These are parenchyma cells between sieve elements.
They act as packing tissue.Transport in Animals
The Circulatory System
Large and complex animals have circulatory systems that consist of tubes, a transport fluid and a means of pumping the fluid.
Blood is the transport fluid which contains dissolved substances and cells.
The tubes are blood vessels through which dissolved substances are circulated around the body.
The heart is the pumping organ which keeps the blood in circulation.MThe types of circulatory system exist in animals: open and closed.
In an open circulatory system;
The heart pumps blood into vessels which open into body spaces known as haemocoel.
Blood comes into contact with tissues.A closed circulatory system;
Found in vertebrates and annelids where the blood is confined within blood vessels and does not come into direct contact with tissues.Transport in Insects
In an insect, there is a tubular heart just above the alimentary canal.
This heart is suspended in a pericardial cavity by ligaments.
The heart has five chambers and extends along the thorax and abdomen .
Blood is pumped forwards into the aorta by waves of contractions in the heart.
It enters the haemocoel and flows towards the posterior.
The blood flows back into the heart through openings in each chamber called ostia.
The ostia have valves which prevent the backflow of blood.
Blood is not used as a medium for transport of oxygen in insects.
This is because oxygen is supplied directly to the tissues by the tracheal system.
The main functions of blood in an insect are to transport nutrients, excretory products and hormones.Mammalian Circulatory System
Mammals have a closed circulatory system where a powerful heart pumps blood into arteries.
The arteries divide into smaller vessels called arterioles.
Each arteriole divides to form a network of capillaries inside the tissues.
The capillaries eventually re-unite to form venules, which form larger vessels called veins.
The veins take the blood back to the heart.
Blood from the heart goes through the pulmonary artery to the lungs and then back to the heart through pulmonary vein.
This circulation is called pulmonary circulation.
Oxygenated blood leaves the heart through the aorta and goes to all the tissues of the body.
From the tissues, deoxygenated blood flows back to the heart through the vena cava.
This circulation is called systemic circulation.
In each complete circulation, the blood flows into the heart twice.
This is called double circulation.
Some other animals like fish have a single circulation.
Blood flows only once through the heart for every complete circuit.Structure and Function of the Heart
The heart has four chambers:
Two artria (auricles) and two ventricles.
The left and right side of the heart are separated by a muscle wall (septum) so that oxygenated and deoxygenated blood does not mix.
Deoxygenated blood from the rest of the body enters the heart through the vena cava .
Blood enters the right atrium, then through tricuspid valve into right ventricle.
Then via semi-lunar valve to the pulmonary artery to the lungs.
Oxygenated blood from the lungs enters the heart through pulmonary vein.
It enters the left atrium of the heart, then through bicuspid valve into left ventricle.
Then via semi-lunar valves to aorta which takes oxygenated blood round the body.
A branch of the aorta called coronary artery supplies blood to the heart muscle.
The coronary vein carries blood from the heart muscle to the pulmonary artery which then takes it to the lungs for oxygenation.Pumping Mechanism of the heart
The heart undergoes contraction (systole) and relaxation ( diastole). Systole
When the ventricular muscles contract, the cuspid valves (tricuspid and bicuspid) close preventing backflow of blood into auricles.
The volume of the ventricles decreases while pressure increases.
This forces blood out of the heart to the lungs through semi-lunar valves and pulmonary artery, and to the body tissues via semi-lunar valve and aorta respectively.
At the same time the atria are filled with blood.
The left ventricle has thicker muscles than the right ventricle, and pumps blood for a longer distance to the tissues.Diastole
When ventricular muscles relax, the volume of each ventricle increases while pressure decreases.
Contractions of atria force the bicuspid and tricuspid valves to open allowing deoxygenated blood from right atrium into right ventricle which oxygenated blood flows from left atrium into the left ventricle.
Semi-lunar valves close preventing the backflow of blood into ventricles.
The slight contractions of atria force the , blood flow into ventricles. The Heartbeat
The heart is capable of contracting and relaxing rhythmically without fatigue due to its special muscles called cardiac muscles.
The rhythmic contraction of the heart arise from within the heart muscles without nervous stimulation.
The contraction is said to be myogenic.
The heartbeat is initiated by the pacemaker or sino-artrio-node (SAN) which is located in the right atrium.
The wave of excitation spreads over the walls of atria.
It is picked by the artrio-ventricular node which is located at the junction:
Of the atria and ventricles, from where the purkinje tissue spreads the wave to the walls of the ventricles.
The heart contracts and relaxes rhythmically at an average rate of 72 times per minute.
The rate of the heartbeat is increased by the sympathetic nerve, while it is slowed down by the vagus nerve.
Heartbeat is also affected by hormones e.g. adrenaline raises the heartbeat.Structure and Function of Arteries,Capillaries and Veins
Arteries
Arteries carry blood away from the heart.
They carry oxygenated blood except pulmonary artery which carries deoxygenated blood to the lungs.
Arteries have a thick, muscular wall, which has elastic and collagen fibres that resist the pressure of the blood flowing in them.
The high pressure is due to the pumping action of the heart.
The pressure in the arteries originate from the pumping action of the heart.
The pulse or number of times the heart beats per minute can be detected by applying pressure on an artery next to the bone.
e.g. by placing the finger/thumb on the wrist.
The innermost layer of the artery is called endothelium which is smooth.
It offers least possible resistance to blood flow.
Have a narrow lumen .
The aorta forms branches which supply blood to all parts of the body.
These arteries divide into arterioles which further divide to form capillaries.Capillaries
Capillaries are small vessels whose walls are made of endothelium which is one cell thick.
This provides a short distance for exchange of substances.
Capillaries penetrate tissues,
The lumen is narrow therefore blood flowing in capillaries is under high pressure.
Pressure forces water and dissolved substances out of the blood to form tissue fluid.
Exchange of substances occurs between cells and tissue fluid.
Part of the tissue fluid pass back into capillaries at the venule end.
Excess fluid drains into small channels called lymph capillaries which empty their contents into lymphatic vessels.
Capillaries join to form larger vessels called venules which in turn join to form veins which transport blood back to the heart.Veins
Veins carry deoxygenated blood from the tissues to the heart (except pulmonary vein which carries oxygenated blood from the lungs to the heart).
Veins have a wider lumen than arteries.
Their walls are thinner than those of arteries.
Blood pressure in the veins is low.
Forward flow of blood in veins is assisted by contraction of skeletal muscles, hence the need for exercise.
Veins have valves along their length to prevent backflow of blood.
This ensures that blood flows towards the heart.
The way the valves work can be demonstrated on the arm.
By pressing on one vein with two fingers, leaving one and pushing blood toward the heart then releasing the latter finger, it can be observed that the part in between is left with the vein not being visible.
This is because bleed does not flow back towards the first finger.Diseases and Defects of Circulatory System
Thrombosis
Formation of a clot in the blood vessels is called thrombosis.
Coronary thrombosis is the most common.
It is caused by blockage of coronary artery which supplies blood to the heart.
Blockage may be due to artery becoming fibrous or accumulation of fatty material on the artery walls.
Narrow coronary artery results in less blood reaching the heart muscles.
A serious blockage can result in heart attack which can be fatal.
Heavy intake of fat, alcohol, being overweight and emotional stress can cause coronary thrombosis.
A blockage in the brain can lead to a stroke causing paralysis of part of the body, coma or even death.
A healthy lifestyle, avoiding a lot of fat in meals and avoiding alcohol can control the disease.Arteriosclerosis
This condition results from the inner walls having materials being deposited there or growth of fibrous connective tissue.
This leads to thickening of the wall of the artery and loss of elasticity.
Normal blood flow is hindered.
Arteriosclerosis can lead to thrombosis or hypertension.
A person with hypertension which is also called high blood pressure has his/her blood being pumped more forcefully through the narrow vessels.
This puts stress on the walls of the heart and arteries.
Regular exercise, healthy diet and avoiding smoking can help maintain normal blood pressure.Varicose Veins
Superficial veins especially at the back of the legs become swollen and flabby due to some valves failing to function properly.
This results to retention of tissue fluid.
Regular physical exercise will prevent this condition.
Repair of valves through surgery can also be done.
Wearing surgical stockings may ease a mild occurence.Structure and Function of Blood
Composition of Blood
The mammalian blood is made up of a fluid medium called plasma with substances dissolved in it.
Cellular components suspended in plasma include;
erythrocytes (red blood cells),
leucocytes (white blood cells)
thrombocytes (platelets)
blood proteins.Plasma
This is a pale yellow fluid consisting of 90% water.
There are dissolved substances which include;
glucose, amino acids, lipids, salts,
hormones, urea, fibrinogen, albumen,
antibodies, some enzymes suspended cells.
Serum is blood from which fibrinogen and cells have been removed.The functions of plasma include:
Transport of red blood cells which carry oxygen.
Transport dissolved food substances round the body.
Transport metabolic wastes like nitrogenous wastes and carbon (IV) oxide in solution about 85% of the carbon (IV) oxide is carried in form of hydrogen carbonates.
Transport hormones from sites of production to target organs.
Regulation of pH of body fluids.
Distributes heat round the body hence regulate body temperature.Erythrocytes (Red Blood Cells)
In humans these cells are circular biconcave discs without nuclei.
Absence of nucleus leaves room for more haemoglobin to be packed in the cell to enable it to carry more oxygen.
Haemoglobin contained in red blood cells is responsible for the transport of oxygen.
Haemoglobin + Oxygen =oxyhaemoglobin
(Hb) + (4O2) __ (HbOg)
Oxygen is carried in form of oxyhaemoglobin.
Haemoglobin readily picks up oxygen in the lungs where concentration of oxygen is high.
In the tissues, the oxyhaemoglobin breaks down (dissociates) easily into haemoglobin and oxygen.
Oxygen diffuses out of the red blood cells into the tissues.
Haemoglobin is then free to pick up more oxygen molecules.
The biconcave shape increases their surface area over which gaseous exchange takes place.
Due to their ability, they are able to change their shape to enable themselves squeeze inside the narrow capillaries.
There are about five million red blood cells per cu bic millimetre of blood.
They are made in the bone marrow of the short bones like sternum, ribs and vertebrae.
In the embryo they are made in the liver and spleen.
Erythrocytes have a life span of about three to four months after which they are destroyed in the liver and spleen.
Also in the red blood cells is carbonic anhydrase which assists in the transport of carbon (IV) oxide.Leucocytes (White Blood Cells)
These white blood cells have a nucleus. They are divided into two:- Granulocytes (also phagocytes or polymorphs) - Agranulocytes .
White blood cells defend the body against disease.
Neutrophils form 70% of the granulocytes.
Others are eosinophils and basophils.
About 24% agronulocytes are called lymphocytes, while 4% agranulocytes are monocytes.
The leucocytes are capable of amoebic movement.
They squeeze between the cells of the capillary wall to enter the intercellular spaces.
They engulf and digest disease causing organisms (pathogens) by phagocytosis.
Some white blood cells may die in the process of phagocytosis.
The dead phagocytes, dead organisms and damaged tissues form pus.
Lymphocytes produce antibodies which inactivate antigens.Antibodies include:
Antitoxins which neutralise toxins.
Agglutinins cause bacteria to clump together and they die.
Lysins digest cell membranes of micro¬organisms.
Opsonins adhere to outer walls of micro¬organisms making it easier for phagocytes to ingest them.
Lymphocytes' are made in the thymus gland and lymph nodes.
There are about 7,000 leucocytes per cubic millimetre of blood.Platelets (Thrombocytes)
Platelets are small irregularly shaped cells formed from large bone marrow cells called megakaryocytes.
There are about 250,000 platelets per cubic millimetre of blood.
They initiate the process of blood clotting.
The process of clotting involves a series of complex reactions whereby fibrinogen is converted into a fibrin clot.
When blood vessels are injured platelets are exposed to air and they release thromboplastin which initiates the blood clotting process.
Thromboplastin neutralises heparin the anti-clotting factor in blood and activates prothrombin to thrombin.
The process requires calcium ions and vitamin K.
Thrombin activates the conversion of fibrinogen to fibrin which forms a meshwork of fibres on the cut surface to trap red blood cells to form a clot.
The clot forms a scab that stops bleeding and protects the damaged tissues from entry of micro-organisms.
Blood clotting reduces loss of blood when blood vessels are injured.
Excessive loss of blood leads to anaemia and dehydration.
Mineral salts lost in blood leads to osmotic imbalance in the body.
This can be corrected through blood transfusion and intravenous fluid.ABO Blood Groups
There are four types of blood groups in human beings: A, B, AB and O.
These are based on types of proteins on the cell membrane of red blood cells.
There are two types of proteins denoted by the letters A and B which are antigens.
In the plasma are antibodies specific to these antigens denoted as a and b.
A person of blood group A has A antigens on the red blood cells and b antibodies in plasma.
A person of blood group B has B antigens on red blood cells and a antibodies in plasma.
A person of blood group AB has A and B antigens on red blood cells and no antibodies in plasma .
A person of blood group a has no antigens on red blood cells and a and b antibodies in plasma.Blood groups
Blood TransfusionBlood transfusion is the transfer of blood from a donor to the circulatory system of the recipient.
A recipient will receive blood from a donor if the recipient has no corresponding antibodies to the donor's antigens.
If the donor's blood and the recipient's blood are not compatible, agglutination occurs whereby red blood cells clump together.
Blood typing
A person of blood group 0 can donate blood to a person of any other blood group.
A person of blood group 0 is called a universal donor.
A person of blood group AB can receive blood from any other group.
A person with blood group AB is called a universal recipient.
A person of blood group A can only donate blood to another person with blood group A or a person with blood group AB.
A person of blood group B can only donate blood to somebody with blood group B or a person with blood group AB.
A person with blood group AB can only donate blood to a person with blood groupAB.
Blood screening has become a very important step in controlling HIV/AIDS.
It is therefore important to properly screen blood before any transfusion is done.Rhesus Factor
The Rhesus factor is present in individuals with the Rhesus antigen in their red blood cells.
Such individuals are said to be Rhesus positive (Rh+), while those without the antigen are Rhesus negative (Rh-).
If blood from an Rh+ individual is introduced into a person who is Rh- , the latter develops antibodies against the Rhesus factor.
There may not be any reaction after this transfusion.
However a subsequent transfusion with Rh+ blood causes a severe reaction, and agglutination occurs i.e. clumping of red blood cells.
The clump can block the flow of blood, and cause death.
Erythroblastosis foetalis (haemolytic disease of the newborn) results when an Rh- mother carries an Rh+ foetus.
This arises when the father is Rh+.
During the latter stage of pregnancy, fragments of Rhesus positive red blood cells of the foetus may enter mother's circulation.
These cause the mother to produce Rhesus antibodies which can pass across the. placenta to the foetus and destroy foetal red blood cells.
During the first pregnancy, enough antibodies are not formed to affect the foetus.
Subsequent pregnancies result in rapid production of Rhesus antibodies by the mother.
These destroy the red blood cells of the foetus, the condition called haemolytic disease of the newborn.
The baby is born anaemic and with yellow eyes (jaundiced).
The condition can be corrected by a complete replacement of baby's blood with safe healthy blood.Lymphatic System
The lymphatic system consists of lymph vessels.
Lymph vessels have valves to ensure unidirectional movement of lymph.
Lymph is excess tissue fluid i.e. blood minus blood cells and plasma proteins.
Flow of lymph is assisted by breathing and muscular contractions.
Swellings called lymph glands occur at certain points along the lymph vessels.
Lymph glands are oval bodies consisting of connective tissues and lymph spaces.
The lymph spaces contain lymphocytes which are phagocytic.
Lymph has the same composition as blood except that it does not contain red blood cells and plasma proteins.Lymph is excess tissue fluid.
Excess tissue fluid is drained into lymph vessels by hydrostatic pressure.
The lymph vessels unite to form major lymphatic system.
The main lymph vessels empty the contents into sub-clavian veins which take it to the heart.Immune Responses
Immune response is the production of antibodies in response to antigens.
An antigen is any foreign material or organism that is introduced into the body and causes the production of antibodies.
Antigens are protein in nature.
An antibody is a protein whose structure is complementary to the antigen.
This means that a specific antibody deals with a specific antigen to make it harmless.
When harmful organisms or proteins invade the body, lymphocytes produce complementary antibodies, while bone marrow and thymus gland produce more phagocytes and lymphocytes respectively.Types of Immunity
There are two types of immunity; natural and artificial. Natural Immunity is also called innate immunity.
It is inherited from parent to offspring. Artificial Immunity can be natural or induced.
When attacked by diseases like chicken pox, measles and mumps, those who recover from these diseases develop resistance to any subsequent infections of the same diseases.
This is natural acquired immunity.Artificial Acquired Immunity:
When attenuated (weakened) or dead micro¬organisms are introduced into a healthy person.
The lymphocytes synthesis the antibodies which are released into the lymph and eventually reach the blood.
The antibodies destroy the invading organisms.
The body retains 'memory' of the structure of antigen.
Rapid response is ensured in subsequent infections.
Vaccines generally contain attenuated disease causing organisms.Artificial Passive Acquired Immunity:
Serum containing antibodies is obtained from another organism, and confers immunity for a short duration.
Such immunity is said to be passive because the body is not activated to produce the antibodies.Importance of Vaccination
A vaccine is made of attenuated, dead or non¬virulent micro-organism that stimulate cells in the immune system to recognise and attack disease causing agent through production of antibodies.
Vaccination protects individuals from infections of many diseases like smallpox, tuberculosis and poliomyelitis.
Diseases like smallpox, tuberculosis and tetanus were killer diseases but this is no longer the case.
Diphtheria Pertussis Tetanus (DPT) vaccine protects children against diphtheria, whooping cough and tetanus.
Bacille Calmette Guerin (BCG) vaccine is injected at birth to children to protect them against tuberculosis.
Measles used to be a killer disease but today, a vaccine injected into children at the age of rune months prevents it.
At birth children are given an inoculation through the mouth of the poliomyelitis vaccine.Allergic Reactions
An allergy is a hypersensitive reaction to an antigen by the body.
The antibody reacts with the antigen violently.
People with allergies are oversensitive to foreign materials like dust, pollen grains, some foods, some drugs and some air pollutants.
Allergic reactions lead to production of histamine by the body.
Histamine causes swelling and pain.
Allergic reactions can be controlled by avoiding the allergen and administration of anti-histamine drugs.
RESPIRATION AND GASEOUS EXCHANGE
Meaning and Significance of Respiration
Respiration is the process by which energy is liberated from organic compounds such as glucose.
It is one of the most important characteristics of living organisms.
Energy is expended (used) whenever an organism exhibits characteristics of life, such as feeding, excretion and movement.
Respiration occurs all the time and if it stops, cellular activities are disrupted due to lack of energy.
This may result in death e.g., if cells in brain lack oxygen that is needed for respiration for a short time, death may occur.
This is because living cells need energy in order to perform the numerous activities necessary to maintain life.
The energy is used in the cells and much of it is also lost as heat.
In humans it is used to maintain a constant body temperature. Tissue Respiration
Respiration takes place inside cells in all tissues.
Every living cell requires energy to stay alive.
Most organisms require oxygen of the air for respiration and this takes place in the mitochondria.Mitochondrion Structure and Function
Structure
Mitochondria are rod-shaped organelles found in the cytoplasm of cells.
A mitochondrion has a smooth outer membrane and a folded inner membrane.
The folding of the inner membrane is called cristae and the inner compartment is called the matrix.Adaptations of Mitochondrion to its Function
The matrix contains DNA ribosomes for making proteins and has enzymes for the breakdown of pyruvate to carbon (IV) oxide, hydrogen ions and electrons.
Cristae increase surface area of mitochondrial inner membranes where attachment of enzymes needed for the transport of hydrogen ions and electrons are found.
There are two types of respiration:
Aerobic Respiration
Anaerobic. RespirationAerobic Respiration
This involves breakdown of organic substances in tissue cells in the presence of oxygen .
All multicellular organisms and most unicellular organisms e.g. some bactena respire aerobically.
In the process, glucose is fully broken down to carbon (IV) oxide and hydrogen which forms water when it combines with the oxygen.
Energy produced is used to make an energy rich compound known as adenosine triphosphate (ATP).
It consists of adenine, an organic base, five carbon ribose-sugar and three phosphate groups.
ATP is synthesised from adenosine diphosphate (ADP) and inorganic phosphate.
The last bond connecting the phosphate group is a high-energy bond.
Cellular activities depend directly on ATP as an energy source.
When an ATP molecule is broken down, it yields energy. Process of Respiration
The breakdown of glucose takes place in many steps.
Each step is catalysed by a specific enzyme.
Energy is released in some of these steps and as a result molecules of ATP are synthesised.
All the steps can be grouped into three main stages:Glycolysis.
The initial steps in the breakdown of glucose are referred to as glycolysis and they take place in the cytoplasm.
Glycolysis consists of reactions in which glucose is gradually broken down into molecules of a carbon compound called pyruvic acid or pyruvate.
Before glucose can be broken, it is first activated through addition of energy from ATP and phosphate groups.
This is referred to as phosphorylation.
The phosphorylated sugar is broken down into two molecules of a 3-carbon sugar (triose sugar) each of which is then converted into pyruvic acid.
If oxygen is present, pyruvic acid is converted into a 2-carbon compound called acetyl coenzyme A (acetyl Co A).
Glycolysis results in the net production of two molecules of ATP.
The next series of reactions involve decarboxylation i.e. removal of carbon as carbon (IV) oxide and dehydrogenation, removal of hydrogen as hydrogen ions and electrons.
These reactions occur in the mitochondria and constitute the Tri-carboxylic Acid Cycle (T.C.A.) or Kreb's citric acid cycle.
The acetyl Co A combines with 4-carbon compound with oxalo-acetic acid to form citric acid - a 6 carbon compound.
The citric acid is incorporated into a cyclical series of reactions that result in removal of carbon (IV) oxide molecules, four pairs of hydrogen, ions and electrons.
Hydrogen ions and electrons are taken to the inner mitochondria membrane where enzymes and electron carriers effect release of a lot of energy.
Hydrogen finally combines with oxygen to form water, and 36 molecules of ATP are synthesised.Anaerobic Respiration
Anaerobic respiration involves breakdown of organic substances in the absence of oxygen.
It takes place in some bacteria and some fungi.
Organisms which obtain energy by anaerobic respiration are referred to as anaerobes.
Obligate anaerobes are those organisms which do not require oxygen at all and may even die if oxygen is present.
Facultative anaerobes are those organisms which survive either in the absence or in the presence of oxygen.
Such organisms tend to thrive better when oxygen is present e.g. yeast.Products of Anaerobic Respiration
The products of anaerobic respiration differ according to whether the process is occurring in plants or animals.Anaerobic Respiration in Plants
Glucose is broken down to an alcohol, (ethanol) and carbon (IV) oxide.
The breakdown is incomplete.
Ethanol is an organic compound, which can be broken down further in the presence of oxygen to provide energy, carbon (IV) oxide and water.C6HI206 _ 2C2H50H + 2C02 + Energy
(Glucose) (Ethanol) (Carbon (IV) oxide)
Fermentation
Is the term used to describe formation of ethanol and carbon (IV) oxide from grains.
Yeast cells have enzymes that bring about anaerobic respiration.Lactate Fermentation
Is the term given to anaerobic respiration in certain bacteria that results in formation of lactic acid.Anaerobic Respiration in Animals
Anaerobic respiration in animals produces lactic acid and energy.C6H1P6 _ 2CH3CHOH.COOH + energy (Glucose) (Lactic acid) + energy
When human muscles are involved in very vigorous activity, oxygen cannot be delivered as rapidly as it is required.
The muscle respire anaerobically and lactic acid accumulates.
A high level of lactic acid is toxic.
During the period of exercise, the body builds up an oxygen debt.
After vigorous activity, one has to breathe faster and deeper to take in more oxygen.
Rapid breathing occurs in order to break down lactic acid into carbon (IV) oxide and water and release more energy.
Oxygen debt therefore refers to the extra oxygen the body takes in after vigorous exercise.Practical Activities
To Show the Gas Produced When the Food is burned
A little food substance e.g., maize flour or meat is placed inside a boiling tube.
The boiling tube is stoppered using a rubber bung connected to a delivery tube inserted into a test-tube with limewater.
The food is heated strongly to bum.
Observations are made on the changes in lime water (calcium hydroxide) as gas is produced.
The clear lime water turns white due to formation of calcium carbonate precipitate proving that carbon (Iv) oxide is produced.Experiment to Show the Gas Produced During Fermentation
Glucose solution is boiled and cooled. Boiling expels all air.
A mixture of glucose and yeast is placed in a boiling tube, and covered with a layer of oil to prevent entry of air.
A delivery tube is connected and directed into a test-tube containing lime water.
The observations are made immediately and after three days the contents are tested for the presence of ethanol.
A control experiment is set in the same way except that yeast which has been boiled and cooled is used.
Boiling kills yeast cells.
The limewater becomes cloudy within 20 minutes.
This proves that carbon (IV) oxide gas is produced.
The fermentation process is confirmed after three days when alcohol smell is detected in the mixture.Experiment to Show Germinating Seeds Produce Heat
Soaked bean seeds are placed in a vacuum flask on wet cotton wool.
A thermometer is inserted and held in place with cotton wool .
The initial temperature is taken and recorded.
A control experiment is set in the same way using boiled and cooled bean seeds which have been washed in formalin to kill micro¬organisms.
Observation is made within three days.
Observations show that temperature in the flask with germinating seeds has risen.
The one in the control has not risen.Comparison Between Aerobic and Anaerobic Respiration
Comparison Between Energy Output in Aerobic and Anaerobic Respiration
Aerobic respiration results in the formation of simple inorganic molecules, water and carbon (Iv) oxide as the by¬products.
These cannot be broken down further. A lot of energy is produced.
When a molecule of glucose is broken down in the presence of oxygen, 2880 KJ of energy are produced (38 molecules of ATP).
In anaerobic respiration the by products are organic compounds.
These can be broken down further in the presence of oxygen to give more energy.
Far less energy is thus produced.
The process is not economical as far as energy production is concerned.
When a molecule of glucose is broken down in the absence of oxygen in plants, 210 KJ are produced (2 molecule ATP).
In animals, anaerobic respiration yields 150 kJ of energy.Substrates for Respiration
Carbohydrate, mainly glucose is the main substrate inside cells.
Lipids i.e. fatty acids and glycerol are also used.
Fatty acids are used when the carbohydrates are exhausted.
A molecule of lipid yields much more energy than a molecule of glucose.
Proteins are not normally used for respiration.
However during starvation they are hydrolysed to amino acids, dearnination follows and the products enter Kreb's cycle as urea is formed.
Use of body protein in respiration result to body wasting, as observed during prolonged sickness or starvation.
The ratio of the amount of carbon (IV) oxide produced to the amount of oxygen used for each substrate is referred to as Respiratory Quotient (RQ) and is calculated as follows:R.Q. = Amount of carbon (IV) oxide produced/ Amount of oxygen used
Carbohydrates have a respiratory quotient of 1.0 lipids 0.7 and proteins 0.8.
Respiratory quotient value can thus give an indication of types of substrate used.
Besides values higher than one indicate that some anaerobic respiration is taking place.Application of Anaerobic Respiration in Industry and at Home Industry
Making of beer and wines.
Ethanol in beer comes from fermentation of sugar(maltose) in germinating barley seeds.
Sugar in fruits is broken down anaerobically to produce ethanol in wines.
In the dairy industry, bacterial fermentation occurs in the production of several dairy products such as cheese, butter and yoghurt.
In production of organic acids e.g., acetic acid, that are used in industry e.g., in preservation of foods.Home
Fermentation of grains is used to produce all kinds of beverages e.g., traditional beer and sour porridge.
Fermentation of milk.End of Topic
Gaseous Exchange in Plants and Animals
Necessity for Gaseous Exchange in Living Organisms
Living organisms require energy to perform cellular activities.
The energy comes from breakdown of food in respiration.
Carbon (IV) oxide is a by product of respiration and its accumulation in cells is harmful which has to be removed.
Most organisms use oxygen for respiration which is obtained from the environment.
Photosynthetic cells of green plants use carbon (Iv) oxide as a raw material for photosynthesis and produce oxygen as a by¬product.
The movement of these gases between the cells of organisms and the environment comprises gaseous exchange.
The process of moving oxygen into the body and carbon (Iv) oxide out of the body is called breathing or ventilation.
Gaseous exchange involves the passage of oxygen and carbon (IV) oxide through a respiratory surface.
Diffusion is the main process involved in gaseous exchange.Gaseous Exchange in Plants
Oxygen is required by plants for the production of energy for cellular activities.
Carbon (IV) oxide is required as a raw material for the synthesis of complex organic substances.
Oxygen and carbon (IV) oxide are obtained from the atmosphere in the case of terrestrial plants and from the surrounding water in the case of aquatic plants.
Gaseous exchange takes place mainly through the stomata.Structure of Guard Cells
The stoma (stomata - plural) is surrounded by a pair of guard cells.
The structure of the guard cells is such that changes in turgor inside the cell cause changes in their shape.
They are joined at the ends and the cell walls facing the pore (inner walls) are thicker and less elastic than the cell walls farther from the pore (outer wall).
Guard cells control the opening and closing of stomata.Mechanism of Opening and Closing of Stomata
In general stomata open during daytime (in light) and close during the night (darkness).
Stomata open when osmotic pressure in guard cells becomes higher than that in surrounding cells due to increase in solute concentration inside guard cells. Water is then drawn into guard cells by osmosis.
Guard cells become turgid and extend.
The thinner outer walls extend more than the thicker walls.
This causes a bulge and stoma opens.
Stomata close when the solute concentration inside guard cells become lower than that of surrounding epidermal cells.
The water moves out by osmosis, and the guard cells shrink i.e. lose their turgidity and stoma closes.Proposed causes of turgor changes in guard cells.
Accumulation of sugar.
Guard cells have chloroplasts while other epidermal cells do not.
Photosynthesis takes place during daytime and sugar produced raises the solute concentration of guard cells.
Water is drawn into guard cells by osmosis from surrounding cells.
Guard cells become turgid and stoma opens.
At night no photosynthesis occurs hence no sugar is produced.
The solute concentration of guard cells falls and water moves out of the guard cells by osmosis.
Guard cells lose turgidity and the stoma closes.pH changes in guard cells occur due to photosynthesis.
In day time carbon (IV) oxide is used for photosynthesis. This reduces acidity while the oxygen produced increases alkalinity.
Alkaline pH favours conversion of starch to sugar.
Solute concentration increases inside guard cells, water is drawn into the cells by osmosis. Guard cells become turgid and the stoma opens.
At night when no photosynthesis, Respiration produces carbon (IV) oxide which raises acidity .This favours conversion of sugar to starch.
low sugar concentration lead to loss of turgidity in guard cells and stoma closes.
Explanation is based on accumulation of potassium ions
In day time (light) adenosine triphosphate (ATP) is produced which causes potassium ions to move into guard cells by active transport.
These ions cause an increase in solute concentration in guard cells that has been shown to cause movement of water into guard cells by osmosis.
Guard cells become turgid and the stoma opens.
At night potassium and chloride ions move out of the guard cells by diffusion and level of organic acid also decreases.
This causes a drop in solute concentration that leads to movement of water out of guard cells by osmosis.
Guard cells lose turgor and the stoma closes.Process of Gaseous Exchange in Root Stem and Leaves of Aquatic and Terrestrial Plants
Gaseous Exchange in leaves of Terrestrial Plants
Gaseous exchange takes place by diffusion.
The structure of the leaf is adapted for gaseous exchange by having intercellular spaces that are filled.
These are many and large in the spongy mesophyll.
When stomata are open,carbon(IV)oxide from the atmosphere diffuses into the substomatal air chambers.
From here, it moves into the intercellular space in the spongy mesophyll layer.
The CO2 goes into solution when it comes into contact with the cell surface and diffuses into the cytoplasm.
A concentration gradient is maintained between the cytoplasm of the cells and the intercellular spaces.
CO2 therefore continues to diffuse into the cells.
The oxygen produced during photosynthesis moves out of the cells and into the intercellular spaces.
From here it moves to the substomatal air chambers and eventually diffuses out of the leaf through the stomata.
At night oxygen enters the cells while CO2 moves out.Gaseous exchange in the leaves of aquatic(floating)plants
Aquatic plants such as water lily have stomata only on the upper leaf surface.
The intercellular spaces in the leaf mesophyll are large.
Gaseous exchange occurs by diffusion just as in terrestrial plants.Observation of internal structure of leaves of aquatic plants
Transverse section of leaves of an aquatic plant such as Nymphaea differs from that of terrestrial plant.The following are some of the features that can be observed in the leave of an aquatic plant;
Absence of cuticle
Palisade mesophyll cells are very close to each other ie.compact.
Air spaces (aerenchyma) in spongy mesophyll are very large.
Sclereids (stone cells) are scattered in leaf surface and project into air spaces.
They strengthen the leaf making it firm and assist it to float.Gaseous Exchange Through Stems Terrestrial Plants
Stems of woody plants have narrow openings or slits at intervals called lenticels.
They are surrounded by loosely arranged cells where the bark is broken.
They have many large air intercellular spaces through which gaseous exchange occurs.
Oxygen enters the cells by diffusion while carbon (IV) oxide leaves.
Unlike the rest of the bark, lenticels are permeable to gases and water.Aquatic Plant Stems
The water lily, Salvia and Wolfia whose stems remain in water are permeable to air and water.
Oxygen dissolved in the water diffuses through the stem into the cells and carbon (IV) oxide diffuses out into the water.Gaseous Exchange in Roots
Terrestrial Plants
Gaseous exchange occurs in the root hair of young terrestrial plants.
Oxygen in the air spaces in the soil dissolves in the film of moisture surrounding soil particles and diffuses into the root hair along a concentration gradient.
It diffuses from root hair cells into the cortex where it is used for respiration.
Carbon (IV) oxide diffuses in the opposite direction.
In older roots of woody plants, gaseous exchange takes place through lenticels.Aquatic Plants
Roots of aquatic plants e.g. water lily are permeable to water and gases.
Oxygen from the water diffuses into roots along a concentration gradient.
Carbon (IV) oxide diffuses out of the roots and into the water.
The roots have many small lateral branches to increase the surface area for gaseous exchange.
They have air spaces that help the plants to float.
Mangroove plants grow in permanently waterlogged soils, muddy beaches and at estuaries.
They have roots that project above the ground level.
These are known as breathing roots or pneumatophores.
These have pores through which gaseous exchange takes place e.g. in Avicenia the tips of the roots have pores.
Others have respiratory roots with large air spaces.Gaseous Exchange in Animals
All animals take in oxygen for oxidation of organic compounds to provide energy for cellular activities.
The carbon (IV) oxide produced as a by-product is harmful to cells and has to be constantly removed from the body.
Most animals have structures that are adapted for taking in oxygen and for removal of carbon (IV) oxide from the body.
These are called "respiratory organs".
The process of taking in oxygen into the body and carbon (IV) oxide out of the body is called breathing or ventilation.
Gaseous exchange involves passage of oxygen and carbon (IV) oxide through a respiratory surface by diffusion.Types and Characteristics of Respiratory surfaces
Different animals have different respiratory surfaces.
The type depends mainly on the habitat of the animal, size, shape and whether body form is complex or simple.
Cell Membrane: In unicellular organisms the cell membrane serves as a respiratory surface.
Gills: Some aquatic animals have gills which may be external as in the tadpole or internal as in bony fish e.g. tilapia.
They are adapted for gaseous exchange in water.
Skin: Animals such as earthworm and tapeworm use the skin or body surface for gaseous exchange.
The skin of the frog is adapted for gaseous exchange both in water and on land.
The frog also uses epithelium lining of the mouth or buccal cavity for gaseous exchange.
Lungs: Mammals, birds and reptiles have lungs which are adapted for gaseous exchange.Characteristics of Respiratory Surfaces
They are permeable to allow entry of gases.
They have a large surface area in order to increase diffusion.
They are usually thin in order to reduce the distance of diffusion.
They are moist to allow gases to dissolve.
They are well-supplied with blood to transport gases and maintain a concentration gradient.Gaseous Exchange in Amoeba
Gaseous exchange occurs across the cell membrane by diffusion.
Oxygen diffuses in and carbon (IV) oxide diffuses out.
Oxygen is used in the cell for respiration making its concentration lower than that in the surrounding water.
Hence oxygen continually enters the cell along a concentration gradient.
Carbon (IV) oxide concentration inside the cell is higher than that in the surrounding water thus it continually diffuses out of the cell along a concentration gradient.Gaseous Exchange in Insects
Gaseous exchange in insects e.g., grasshopper takes place across a system of tubes penetrating into the body known as the tracheal system.
The main trachea communicate with atmosphere through tiny pores called spiracles.
Spiracles are located at the sides of body segments;
Two pairs on the thoracic segments and eight pairs on the sides of abdominal segments.
Each spiracle lies in a cavity from which the trachea arises.
Spiracles are guarded with valves that close and thus prevent excessive loss of water vapour.
A filtering apparatus i.e. hairs also traps dust and parasites which would clog the trachea if they gained entry.
The valves are operated by action of paired muscles.Mechanism of Gaseous Exchange in Insects
The main tracheae in the locust are located laterally along the length of the body on each side and they are interconnected across.
Each main trachea divides to form smaller tracheae, each of which branches into tiny tubes called tracheoles.
Each tracheole branches further to form a network that penetrates the tissues. Some tracheoles penetrate into cells in active tissue such as flight muscles.
These are referred to as intracellular tracheoles.
Tracheoles in between the cells are known as intercellular tracheoles.
The main tracheae are strengthened with rings of cuticle.
This helps them to remain open during expiration when air pressure is low.Adaptation of Insect Tracheoles for Gaseous Exchange
The fine tracheoles are very thin about one micron in diameter in order to permeate tissue.
They are made up of a single epithelial layer and have no spiral thickening to allow diffusion of gases.
Terminal ends of the fine tracheoles are filled with a fluid in which gases dissolve to allow diffusion of oxygen into the cells.
Amount of fluid at the ends of fine tracheoles varies according to activity i.e. oxygen demand of the insect.
During flight, some of the fluid is withdrawn from the tracheoles such that oxygen reaches muscle cells faster and the rate of respiration is increased.
In some insects, tracheoles widen at certain places to form air sacs.
These are inflated or deflated to facilitate gaseous exchange as need arises.
Atmospheric air that dissolves in the fluid at the end of tracheoles has more oxygen than the surrounding cells of tracheole epithelium'.
Oxygen diffuses into these cells along a concentration gradient. '
Carbon (IV) oxide concentration inside the cells is higher than in the atmospheric .
Air and diffuses out of the cells along a concentration gradient.
It is then removed with expired air.Ventilation in Insects
Ventilation in insects is brought about by the contraction and relaxation of the abdominal muscles.
In locusts, air is drawn into the body through the thoracic spiracles and expelled through the abdominal spiracles.
Air enters and leaves the tracheae as abdominal muscles contract and relax.
The muscles contract laterally so the abdomen becomes wider and when they relax it becomes narrow.
Relaxation of muscles results in low pressure hence inspiration occurs while contraction of muscles results in higher air pressure and expiration occurs.
In locusts, air enters through spiracles in the thorax during inspiration and leaves through the abdominal spiracles during expiration.
This results in efficient ventilation.
Maximum extraction of oxygen from the air occurs sometimes when all spiracles close and hence contraction of abdominal muscles results in air circulating within the tracheoles.
The valves in the spiracles regulate the opening and closing of spiracles. Observation of Spiracle in Locust
Some fresh grass is placed in a gas jar.
A locust is introduced into the jar.
A wire mesh is placed on top or muslin cloth tied around the mouth of the beaker with rubber band.
The insect is left to settle.
Students can approach and observe in silence the spiracles and the abdominal movements during breathing.
Alternatively the locust is held by the legs and observation of spiracles is made by the aid of hand lens.Gaseous Exchange in Bony Fish (e.g, Tilapia)
Gaseous exchange in fish takes place between the gills and the surrounding water.
The gills are located in an opercular cavity covered by a flap of skin called the operculum.
Each _gill consists of a number of thin leaf-like lamellae projecting from a skeletal base branchial arch (gill bar) situated in the wall of the pharynx.
There are four gills within the opercular cavity on each side of the head.
Each gill is made up of a bony gill arch which has a concave surface facing the mouth cavity (anterior) and a convex posterior surface.
Gill rakers are bony projections on the concave side that trap food and other solid particles which are swallowed instead of going over and damaging the gill filaments.
Two rows of gill filaments subtend from the convex surface.Adaptation of Gills for Gaseous Exchange
Gill filaments are thin walled.
Gill filaments are very many (about seventy pairs on each gill), to increase surface area.
Each gill filament has very many gill lamellae that further increase surface area.
The gill filaments are served by a dense network of blood vessels that ensure efficient transport of gases.
It also ensures that a favourable diffusion gradient is maintained.
The direction of flow of blood in the gill lamellae is in the opposite direction to that of the water (counter current flow) to ensure maximum diffusion of gases.Ventilation
As the fish opens the mouth, the floor of the mouth is lowered.
This increases the volume of the buccal cavity.
Pressure inside the mouth is lowered causing water to be drawn into the buccal cavity.
Meanwhile, the operculum is closed, preventing water from entering or leaving through the opening.
As the mouth closes and the floor of the mouth is raised, the volume of buccal cavity decreases while pressure in the opercular cavity increases due to contraction of opercular muscles.
The operculum is forced to open and water escapes.
As water passes over the gills, oxygen is absorbed and carbon dioxide from the gills dissolves in the water.
As the water flows over the gill filaments oxygen in the water is at a higher concentration than that in the blood flowing, in the gill.
Oxygen diffuses through the thin walls of gill filaments/lamellae into the blood.
Carbon (IV) oxide is at a higher concentration in the blood than in the water.
It diffuses out of blood through walls of gill filaments into the water.Counter Current Flow
In the bony fish direction of flow of water over the gills is opposite that of blood flow through the gill filaments .
This adaptation ensures that maximum amount of oxygen diffuses from the water into the blood in the gill filament.
This ensures efficient uptake of oxygen from the water.
Where the flow is along the same direction (parallel flow) less oxygen is extracted from the water.Observation of Gills of a Bony Fish (Tilapia)
Gills of a fresh fish are removed and placed in a petri-dish with enough water to cover them.
A hand lens is used to view the gills.
Gill bar, gill rakers and two rows of gill filaments are observed.Gaseous Exchange in an Amphibian - Frog
An adult frog lives on land but goes back into the water during the breeding season.
A frog uses three different respiratory surfaces.
These are the skin, buccal cavity and lungs.Skin
The skin is used both in water and on land.
It is quite efficient and accounts for 60% of the oxygen taken in while on land.Adaptations of a Frog's Skin for Gaseous Exchange
The skin is a thin epithelium to allow fast diffusion.
The skin between the digits in the limbs (i.e. webbed feet) increase the surface area for gaseous exchange.
It is richly supplied with blood vessels for transport of respiratory gases.
The skin is kept moist by secretions from mucus glands.
This allows for respiratory gases to dissolve.
Oxygen dissolved in the film of moisture diffuses across the thin epithelium and into the blood which has a lower concentration of oxygen.
Carbon (IV) oxide diffuses from the blood across the skin to the atmosphere along the concentration gradient.Buccal (Mouth) Cavity
Gaseous exchange takes place all the time across thin epithelium lining the mouth cavity.
Adaptations of Buccal Cavity for Gaseous Exchange
It has a thin epithelium lining the walls of the mouth cavity allowing fast diffusion of gases.
It is kept moist by secretions from the epithelium for dissolving respiratory gases.
It has a rich supply of blood vessels for efficient transport of respiratory gases.
The concentration of oxygen in the air within the mouth cavity is higher than that of the blood inside the blood vessels.
Oxygen, therefore dissolves in the moisture lining the mouth cavity and then diffuses into the blood through the thin epithelium.
On the other hand, carbon (IV) oxide diffuses in the opposite direction along a concentration gradient.Lungs
There is a pair of small lungs used for gaseous exchange.Adaptation of Lungs
The lungs are thin walled for fast diffusion of gases.
Have internal foldings to increase surface area for gaseous exchange.
A rich supply of blood capillaries for efficient transport of gases.
Moisture lining for gases to dissolve.Ventilation
Inspiration
During inspiration, the floor of the mouth is lowered and air is drawn in through the nostrils.
When the nostrils are closed and the floor of the mouth is raised, air is forced into the lungs.
Gaseous exchange occurs in the lungs, oxygen dissolves in the moisture lining of the lung and diffuses into the blood through the thin walls.
Carbon (IV) oxide diffuses from blood into the lung lumen.Expiration
When the nostrils are closed and the floor of mouth is lowered by contraction of its muscles, volume of mouth cavity increases.
Abdominal organs press against the lungs and force air out of the lungs into buccal cavity.
Nostrils open and floor of the mouth is raised as its muscles relax.
Air is forced out through the nostrils.Gaseous Exchange in a Mammal -Human
The breathing system of a mammal consists of a pair of lungs which are thin-walled elastic sacs lying in the thoracic cavity.
The thoracic cavity consists of vertebrae, sternum, ribs and intercostal muscles.
The thoracic cavity is separated from the abdominal cavity by the diaphragm.
The lungs lie within the thoracic cavity.
They are enclosed and protected by the ribs which are attached to the sternum and the thoracic vertebrae.
There are twelve pairs of ribs, the last two pairs are called 'floating ribs' because they are only attached to the vertebral column.
The ribs are attached to and covered by internal and external intercostals muscles.
The diaphragm at the floor of thoracic cavity consists of a muscLe sheet at the periphery and a central circular fibrous tissue.
The muscles of the diaphragm are attached to the thorax wall.
The lungs communicate with the outside atmosphere through the bronchi, trachea, mouth and nasal cavities.
The trachea opens into the mouth cavity through the larynx.
A flap of muscles, the epiglottis, covers the opening into the trachea during swallowing.
This prevents entry of food into the trachea.
Nasal cavities are connected to the atmosphere through the external nares(or nostrils)which are lined with hairs and mucus that trap dust particles and bacteria, preventing them from entering into the lungs.
Nasal cavities are lined with cilia.
The mucus traps dust particles,
The cilia move the mucus up and out of the nasal cavities.
The mucus moistens air as it enters the nostrils.
Nasal cavities are winding and have many blood capillaries to increase surface area to ensure that the air is warmed as it passes along.
Each lung is surrounded by a space called the pleural cavity.
It allows for the changes in lung volume during breathing.
An internal pleural membrane covers the outside of each lung while an external pleural membrane lines the thoracic wall.
The pleural membranes secrete pleural fluid into the pleural cavity.
This fluid prevents friction between the lungs and the thoracic wall during breathing.
The trachea divides into two bronchi, each of which enters into each lung.
Trachea and bronchi are lined with rings of cartilage that prevent them from collapsing when air pressure is low.
Each bronchus divides into smaller tubes, the bronchioles.
Each bronchiole subdivides repeatedly into smaller tubes ending with fine bronchioles.
The fine bronchioles end in alveolar sacs, each of which gives rise to many alveoli.
Epithelium lining the inside of the trachea, bronchi and bronchioles has cilia and secretes mucus.Adaptations of Alveolus to Gaseous Exchange
Each alveolus is surrounded by very many blood capillaries for efficient transport of respiratory gases.
There are very many alveoli that greatly increases the surface area for gaseous exchange.
The alveolus is thin walled for faster diffusion of respiratory gases.
The epithelium is moist for gases to dissolve.Gaseous Exchange Between the Alveoli and the Capillaries
The walls of the alveoli and the capillaries are very thin and very close to each other.
Blood from the tissues has a high concentration of carbon (IV) oxide and very little oxygen compared to alveolar air.
The concentration gradient favours diffusion of carbon (IV) oxide into the alveolus and oxygen into the capillaries .
No gaseous exchange takes place in the trachea and bronchi.
These are referred to as dead space. Ventilation
Exchange of air between the lungs and the outside is made possible by changes in the volumes of the thoracic cavity.
This volume is altered by the movement of the intercostal muscles and the diaphragm.Inspiration
The ribs are raised upwards and outwards by the contraction of the external intercostal muscles, accompanied by the relaxation of internal intercostal muscles.
The diaphragm muscles contract and diaphragm moves downwards.
The volume of thoracic cavity increases, thus reducing the pressure.
Air rushes into the lungs from outside through the nostrils.Expiration
The internal intercostal muscles contract while external ones relax and the ribs move downwards and inwards.
The diaphragm muscles relaxes and it is pushed upwards by the abdominal organs. It thus assumes a dome shape.
The volume of the thoracic cavity decreases, thus increasing the pressure.
Air is forced out of the lungs.
As a result of gaseous exchange in the alveolus, expired air has different volumes of atmospheric gases as compared to inspired air.
Lung Capacity
The amount of air that human lungs can hold is known as lung capacity.
The lungs of an adult human are capable of holding 5,000 cm3 of air when fully inflated.
However, during normal breathing only about 500 cm3 of air is exchanged.
This is known as the tidal volume.
A small amount of air always remains in the lungs even after a forced expiration.
This is known as the residual volume.
The volume of air inspired or expired during forced breathing is called vital capacity.Control of Rate Of Breathing
The rate of breathing is controlled by the respiratory centre in the medulla of the brain.
This centre sends impulses to the diaphragm through the phrenic nerve.
Impulses are also sent to the intercostal muscles.
The respiratory centre responds to the amount of carbon (IV) oxide in the blood.
If the amount of carbon (IV) oxide rises, the respiratory centre sends impulses to the diaphragm and the intercostal muscles which respond by contracting in order to increase the ventilation rate.
Carbon (IV) oxide is therefore removed at a faster rate.Factors Affecting Rate of Breathing in Humans
Factors that cause a decrease or increase in energy demand directly affect rate of breathing.
Exercise, any muscular activity like digging.
Sickness
Emotions like anger, flight
Sleep.Effects of Exercise on Rate of Breathing
Students to work in pairs.
One student stands still while the other counts (his/her) the number of breaths per minute.
The student whose breath has been taken runs on the sport vigorously for 10 minutes.
At the end of 10 minutes the number of breaths per minute is immediately counted and recorded.
It is noticed that the rate of breathing is much higher after exercise than at rest.Dissection of a Small Mammal (Rabbit) to Show Respiratory Organs
The rabbit is placed in a bucket containing cotton wool which has been soaked in chloroform.
The bucket is covered tightly with a lid.
The dead rabbit is placed on the dissecting board ventral side upwards.
Pin the rabbit to the dissecting board by the legs.
Dissect the rabbit to expose the respiratory organs.
Ensure that you note the following features.
Ribs, intercostal muscles, diaphragm, lungs, bronchi, trachea, pleural membranes, thoracic cavity.Diseases of the Respiratory System
Asthma
Asthma is a chronic disease characterised by narrowing of air passages.Causes:
Allergy
Due to pollen, dust, fur, animal hair, spores among others.
If these substances are inhaled, they trigger release of chemical substances and they may cause swelling of the bronchioles and bring about an asthma attack. Heredity
Asthma is usually associated with certain disorders which tend to occur in more than one member of a given family, thus suggesting' a hereditary tendency.Emotional or mental stress
Strains the body immune system hence predisposes to asthma attack.Symptoms
Asthma is characterized by wheezing and difficulty in breathing accompanied by feeling of tightness in the chest as a result of contraction of the smooth muscles lining the air passages.Treatment and Control
There is no definite cure for asthma.
The best way where applicable is to avoid whatever triggers an attack (allergen).
Treatment is usually by administering drugs called bronchodilators.
The drugs are inhaled, taken orally or injected intravenously depending on severity of attack to relief bronchial spasms.Bronchitis
This is an inflammation of bronchial tubes.Causes
This is due to an infection of bronchi and bronchioles by bacteria and viruses.Symptoms
Difficulty in breathing.
Cough that produces mucus.Treatment
Antibiotics are administered.Pulmonary Tuberculosis
Tuberculosis is a contagious disease that results in destruction of the lung tissue.Causes
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis.
Human tuberculosis is spread through droplet infection i.e., in saliva and sputum.
Tuberculosis can also spread from cattle to man through contaminated milk.
From a mother suffering from the disease to a baby through breast feeding.
The disease is currently on the rise due to the lowered immunity in persons with HIV and AIDS (Human Immuno Deficiency Syndrome).
Tuberculosis is common in areas where there is dirt, overcrowding and malnourishment.Symptoms
It is characterised by a dry cough, lack of breath and body wasting.Prevention
Proper nutrition with a diet rich in proteins and vitamins to boost immunity.
Isolation of sick persons reduces its spread.
Utensils used by the sick should be sterilised by boiling.
Avoidance of crowded places and living in well ventilated houses.
Immunisation with B.C.G. vaccine gives protection against tuberculosis.
This is done a few days after birth with subsequent boosters.Treatment
Treatment is by use of antibiotics.Pneumonia
Pneumonia is infection resulting in inflammation of lungs.
The alveoli get filled with fluid and bacterial cells decreasing surface are for gaseous exchange.
Pneumonia is caused by bacteria and virus.
More infections occur during cold weather.
The old and the weak in health are most vulnerable.Symptoms
Pain in the chest accompanied by a fever, high body temperatures (39-40°C) and general body weakness.Prevention
Maintain good health through proper feeding.
Avoid extreme cold.Treatment
If the condition is caused by pneumococcus bacteria, antibiotics are administered.
If breathing is difficult, oxygen may be given using an oxygen mask.Whooping Cough
Whooping cough is an acute infection of respiratory tract.
The disease is more common in children under the age of five but adults may also be affected.Causes
It is caused by Bordetella pertusis bacteria and is usually spread by droplets produced when a sick person coughs.Symptoms:
Severe coughing and frequent vomiting.
Thick sticky mucus is produced.
Severe broncho-pneumonia.
Convulsions in some cases.Prevention
Children may be immunised against whooping cough by means of a vaccine which is usually combined with those against diphtheria and tetanus.
It is called "Triple Vaccine" or Diptheria, Pertusis and Tetanus (DPT).Treatment
Antibiotics are administered.
To reduce the coughing, the patient should be given drugs.Practical Activities Observation of permanent slides of terrestrial and aquatic leaves and stems Leaves
Observation of T.S. of bean and water lily are made under low and 'medium power objectives. Stomata and air space are seen.
Labelled drawings of each are made.
The number and distribution of stomata on the lower and upper leaf surface is noted.
Also the size of air spaces and their distribution. Stem
Prepared slides (TS) of stems of terrestrial and aquatic plants such as croton and reeds are obtained.
Observations under low power and medium power of a microscope are made.
Labelled drawings are made and the following are noted:
Lenticels on terrestrial stems.
Large air spaces (aerenchyma) in aquatic stems.
Excretion and Homeostasis
Introduction
Excretion is the process by which living organisms separate and eliminate waste products of metabolism from body cells.
If these substances were left to accumulate, they would be toxic to the cells.
Egestion is the removal of undigested materials from the alimentary canals of animals.
Secretion is the production and release of certain useful substances such as hormones, sebum and mucus produced by glandular cells.
Homeostasis is a self-adjusting mechanism to maintain a steady state in the internal environmentExcretion in Plants
Plants have little accumulation of toxic waste especially nitrogenous wastes.
This is because they synthesise proteins according to their requirements.
In carbohydrate metabolism plants use carbon (IV) oxide released from respiration in photosynthesis while oxygen released from photosynthesis is used in respiration.
Gases are removed from the plant by diffusion through stomata and lenticels.
Certain organic products are stored in plant organs such as leaves, flowers, fruits and bark and are removed when these organs are shed.
The products include tannins, resins, latex and oxalic acid crystals.
Some of these substances are used illegally.
Khat, cocaine and cannabis are used without a doctor's prescription and can be addictive.
Use of these substances should be avoided.Plant Excretory Products their source and uses
Excretion and Homeostasis in Unicellular Organisms
Protozoa such as amoeba depend on diffusion as a means of excretion.
They have a large surface area to volume ratio for efficient diffusion.
Nitrogenous waste and carbon (IV) oxide are highly concentrated in the organism hence they diffuse out.
In amoeba excess water and chemicals accumulation in the contractile vacuole.
When it reaches maximum size the contractile vacuole moves to the cell membrane, bursts open releasing its contents to the surroundings.Excretion in Human Beings
Excretion in humans is carried out by an elaborate system of specialised organs.
Their bodies are complex, so simple diffusion cannot suffice.
Excretory products include nitrogenous wastes which originate from deamination of excess amino acids.
The main excretory organs in mammals such as human beings include lungs, kidneys, skin and liver.Structure and function of the human skin
Nerve Endings:
These are nerve cells which detect changes from the external environment thus making the body to be sensitive to touch, cold, heat and pressure.Subcutaneous Fat:
Is a layer beneath the dermis.
It stores fat and acts as an insulator against heat loss.
The skin helps in elimination of urea, lactic acid and sodium chloride which are released in sweat.The Lungs
Carbon (IV) oxide formed during tissue respiration is removed from the body by the lungs.
Mammalian lungs have many alveoli which are the sites of gaseous exchange.
Alveoli are richly supplied with blood and have a thin epithelium.
Blood capillaries around the alveoli have a high concentration of carbon (Iv) oxide than the alveoli lumen.
The concentration gradient created causes carbon (IV) oxide to diffuse into the alveoli lumen.
The carbon (IV) oxide is eliminated through expiration.Structure and Functions of the Kidneys
The kidneys are organs whose functions are excretion, osmoregulation and regulation of pH.
Kidneys are located at the back of the abdominal cavity.
Each kidney receives oxygenated blood from renal artery,
while deoxygenated blood leaves through the renal vein.
Urine is carried by the ureter from the kidney to the bladder, which temporarily stores it.
From the bladder, the urine is released to the outside via the urethra.
The opening from the urethra is controlled by a ring-like sphincter muscle.
A longitudinal section of the kidney shows three distinct regions: a darker outer cortex, a lighter inner medulla and the pelvis.
The pelvis is a collecting space leading to the ureter which takes the urine to the bladder from where it is eliminated through the urethra.The Nephron
A nephron is a coiled tubule at one end of which is a cup-shaped structure called the Bowman's capsule.
The capsule encloses a bunch of capillaries called the glomerulus.
The glomerulus receives blood from an afferent arteriole a branch of the renal artery.
Blood is taken away from the glomerulus by efferent arteriole leading to the renal vein.
The Bowman's capsule leads to the proximal convoluted tubule that is coiled and extends into a U-shaped part called loop of Henle.
From the loop of Henle is the distal convoluted tubule that is also coiled.
This leads to the collecting duct which receives contents of many nephrons.
Collecting ducts lead to the pelvis of the kidney.Mechanism of Excretion
Excretion takes place in three steps:
Filtration, reabsorption and removal. Filtration
The kidneys receive blood from renal artery a branch of the aorta.
This blood is rich in nitrogenous waste e.g. urea.
It contains dissolved food substances, plasma proteins,hormones and oxygen.
Blood flow in capillaries is under pressure due to the narrowness of the capillaries.
The afferent arteriole entering the glomerulus is wider than the efferent arteriole leaving it.
This creates pressure in the glomerulus.
Due to this pressure, dissolved substances such as urea, uric acid, glucose, mineral salts and amino acids are forced out of the glomerulus into the Bowman's capsule.
Large sized molecules in the plasma such as proteins and red blood cells are not filtered out because they are too large.
This process of filtration is called ultra-filtration or pressure filtration and the filtrate is called glomerular filtrate.Selective Reabsorption
As the filtrate flows through the renal tubules the useful substances are selectively reabsorbed back into the blood.
In the proximal convoluted tube all the glucose, all amino acids and some mineral salts are actively reabsorbed by active transport.
The cells lining this tubule have numerous mitochondria which provide the energy needed.
Cells of the tubule have microvilli which increases the surface area for re-absorption.
The tubule is coiled, which reduces the speed of flow of the filtrate e.g. giving more time for efficient re-absorption.
The tubule is well supplied with blood capillaries for transportation of reabsorbed substances.
The ascending loop has thick wall and is impermeable to water.
Sodium is actively pumped out of it towards the descending loop.
As glomerular filtrate moves down the descending loop, water is reabsorbed into the blood by osmosis in the distal convoluted tubule and in the collecting duct.
Permeability of the collecting duct and proximal convoluted tubule is increased by anti-diuretic hormone (ADH) whose secretion is influenced by the osmotic pressure of the blood.
The remaining fluid consisting of water, urea, uric acid and some mineral salts is called urine.
The urine is discharged into the collecting d ct and carried to the pelvis.
The loop of Henle is short in semi¬-aquatic mammals, and long in some mammals like the desert rat.Removal
The urine is conveyed from the pelvis to the ureter.
The ureter carries the urine to the bladder where it is stored temporarily and discharged to the outside through the urethra at intervals.Common Kidney Diseases
Uraemia
This is a condition in which concentration of urea in the blood.
It may be due to formation of cysts in tubules or reduction in blood supply to the glomeruli as a result of contraction of renal artery.Symptoms
Symptoms include yellow colouration of skin, smell of urine in breath, nausea and vomiting.
Treatment includes dialysis to remove excess urea and a diet low in proteins and salts especially sodium and potassium.Kidney Stones
Kidney stones are solid deposits of calcium and other saIts.
They are usually formed in the pelvis of the kidney where they may obstruct the flow of urine.Causes: the stones are formed due to crystallisation of salts around pus, blood or dead tissue.
Symptoms: include blood in urine, frequent urination, pain, chills and fever. Severe pain when urinating.
Treatment
Use of laser beams to disintegrate the stones.
Pain killing drugs like morphine.
Stones can be removed by surgery.
Taking hot baths and massage.Nephritis
Nephritis is the inflation of glomerulus of the kidney.Causes: Bacterial infection, sore throat or tonsillitis, blockage of glomeruli by antibody-antigen complex.
Signs and Symptoms: include headaches, fever, vomiting, oedema.
Control includes dietary restrictions especially salt and proteins.
Prompt treatment of bacterial infections.Role of Liver in Excretion
The liver lies below the diaphragm and it receives blood from hepatic artery and hepatic portal vein.
Blood flows out of the liver through hepatic vein.
Excretion of Nitrogenous Wastes
Excess amino acids cannot be stored in the body, they are deaminated in the liver.
Hydrogen is added to amino group to form ammonia which combines with carbon (IV) oxide to form urea.
The urea is carried in the blood stream to the kidneys.
The remaining carboxyl group, after removal of amino group, is either oxidised to provide energy in respiration.
or built up into carbohydrate reserve and stored as glycogen or converted into fat and stored.Breakdown and Elimination of Haemoglobin
Haemoglobin is released from dead or old red blood cells which are broken down in the liver and spleen.
Haemoglobin is broken down in the liver and a green pigment biliverdin results which is converted to yellow bilirubin.
This is taken to the gall bladder and eliminated as bile.Elimination of Sex Hormones
Once they have completed their functions, sex hormones are chemically altered by the liver and then taken to the kidney for excretion.Common Liver Diseases
Cirrhosis
Cirrhosis is a condition in which liver cells degenerate and are replaced by scar tissue .
This causes the liver to shrink, harden, become fibrous and fail to carry out its functions. Causes
Chronic alcohol abuse, schistosomiasis infection, obstruction of gall-bladder.Symptoms
Headache, nausea, vomiting of blood and lack of appetite, weight loss, indigestion and jaundice.Control and Treatment
Avoid alcohol consumption and fatty diet.
Use drugs to kill the schistosomes if that is the cause.Jaundice
This is a yellow colouration of the skin and eyes.Cause: Presence of excess bile pigments.
This happens due to blockage of bile duct or destruction of liver.Symptoms: Yellow pigmentation of skin and eyes, nausea, vomiting and lack of appetite. Itching of skin.
Treatment
Removal of stones from the gall bladder by surgery.
Give patient fat-free diet, reduced amount of proteins.
Give antihistamines to reduce itching.Homeostasis
Homeostasis is the maintenance of a constant internal environment.
The internal environment consists of intercellular or tissue fluid.
This fluid is the medium in the space surrounding cells.
Tissue fluid is made by ultra-filtration in the capillaries.
Dissolved substances in the blood are forced out of the capillaries and into intercellular spaces.
Cells obtain their requirements from tissue fluid while waste products from cells diffuse out into the tissue fluid.
Some of the fluid gets back into the blood capillaries while excess fluid is drained into the lymph vessels.
Cells function efficiently if there is little or no fluctuation in the internal environment.
The factors that need to be regulated include temperature, osmotic pressure and pH.
The body works as a self-regulating system and can detect changes in its working conditions bringing about corrective responses.
This requires a negative feedback mechanism e.g. when body temperature falls below normal, mechanisms are set in place that bring about increase in temperature.
And when the increase is above normal, mechanisms that lower the temperature are set in place.
This is called a negative feedback and it restores the conditions to normal.Neuro-Endocrine System and Homeostasis
Homeostatic mechanisms are brought about by an interaction between nervous and endocrine systems.
Nerve endings detect changes in the internal and external environment and relay the information to the brain.
The hypothalamus and pituitary are endocrine glands situated in the brain.
The hypothalamus detect changes in the blood.
The pituitary secretes a number of hormones involved in homeostasis e.g. anti-duretic hormone (ADH).
The discussion below shows the nature of these interactions.The Skin and Temperature Regulation
The optimum human body temperature is 36.8°C.
A constant body temperature favours efficient enzyme reaction.
Temperatures above optimum denature enzymes, while temperature below the optimum range inactivate enzymes.
The skin is involved in regulation of body temperature as follows:
The skin has receptors that detect changes in the temperature of the external environment.When the body temperature is above optimum the following takes place:
Sweat:
Sweat glands secrete sweat onto the skin surface.
As sweat evaporates it takes latent heat from the body, thus lowering the temperature.Vasodilation of Arterioles:
The arterioles near the surface become wider in diameter.
More blood flows near the surface and more heat is lost to the surrounding by convection and radiation.Relaxation of hair erector muscle:
When hair erector muscles relax, the hair lies flat thus allowing heat to escape from the skin surface.When body temperature is below optimum the following takes place:
Vasoconstriction of Arterioles:
The arterioles near the surface of the skin become narrower.
Blood supply to the skin is reduced and less heat is lost to the surroundings. Contraction of hair erector muscles.
When hair erector muscles contract, the hair is raised.
Air is trapped between the hairs forming an insulating layer.
Animals in cold areas have a thick layer of subcutaneous fat, which helps to insulate the body.
Besides the role of the skin in thermoregulation as discussed above, the rate of metabolism is lowered when temperature is above optimum and increased when temperature is below optimum.
The latter increases the temperature to the optimum.
When this fails, shivering occurs.
Shivering is involuntary contraction of muscles which helps to generate heat thus raising the body temperature.Homeostatic Control of Body Temperature in Humans
Body size and Heat Loss
The amount of heat produced by metabolic reactions in an animal body is proportional to its mass.
Large animals produce more heat but they lose less due to small surface area to volume ratio.
Small animals produce less heat and lose a lot, due to large surface area to volume ratio.
Small animals eat a lot of food in relation .to their size in order to raise their metabolic rate. Behavioural and Physiological Responses to Temperature Changes
Animals gain or lose heat to the environment by conduction, radiation and convection.
Birds and mammals maintain a constant body temperature regardless of the changes in the environment.
They do this mainly by internally installed physiological mechanisms hence they are endotherms, also known as homoiotherms.
At the same time behavioural activities like moving to shaded areas when it is too hot assist in regulating their body temperature.
Other animals do not maintain a constant body temperature e.g. lizards.
They are poikilotherms (ectotherms) as their temperature varies according to that of surroundings.
They only regulate body temperature through behavioural means.
Lizards bask on the rocks to gain heat and hide under rocks when it is too hot.
Some animals have adaptive features e.g. animals in extreme cold climates have fur and a thick layer of subcutaneous fat like polar bear.
Those in extremely hot areas have tissue that tolerate high temperatures e.g. camels.
Some animals avoid cold conditions by hibernating e.g. the frog while others avoid dry hot conditions by aestivation e.g. kangaroo rat.
This involves decreasing their metabolic activities.Skin and Osmoregulation
Osmoregulation is the control of salt and water balance in the body to maintain the appropriate osmotic pressure for proper cell functioning.
Sweat glands produce sweat and thus eliminate water and salt from the body.The Kidney and Osmoregulation
The kidney is the main organ that regulates the salt and water balance in the body.
The amount of salt or water reabsorbed into the bloodstream is dependent on the osmotic pressure of the blood.
When the osmotic pressure of the blood rises above normal due to dehydration or excessive consumption of salt, the osmo-receptors in the hypothalamus are stimulated.
These cells relay impulses to the pituitary gland which produces a hormone called anti-diuretic hormone - ADH (vasopressin) which is taken by the blood to the kidneys.
The hormone (ADH) makes the distal convoluted tubule and collecting duct more permeable to water hence more water is reabsorbed into the body by the kidney tubules lowering the osmotic pressure in the blood.
When the osmotic pressure of the blood falls below normal due to intake of a large quantity of water, osmoreceptors in the hypothalamus are less stimulated.
Less antidiuretic hormone is produced, and the kidney tubules reabsorb less water hence large quantities of water is lost producing dilute urine (diuressis).
The osmotic pressure of the blood is raised to normal.
If little or no ADH is produced, the body may become dehydrated unless large quantities of water are consumed regularly.Diabetes insipidus is a disease that results from the failure of the pituitary gland to produce ADH and the body gets dehydrated.
A hormone called Aldosterone produced by the adrenal cortex regulates the level of sodium ions.
When the level of sodium ions in the blood is low, adrenal cortex releases aldosterone into the blood.
This stimulates the loop of Henle to reabsorb sodium ions into the blood.
Chloride ions flow to neutralise the charge on sodium ions.
Aldosterone also stimulates the colon to absorb more sodium ions into the blood.
If the sodium ion concentration rises above optimum level, adrenal cortex
Notes missing - The liver
Formation of Red Blood Cells.
In the embryo, red blood cells are formed in the liver.
Breakdown and elimination of old and dead blood cells.
Dead red blood cells are broken down in the liver and the pigments eliminated in bile.Manufacture of Plasma Proteins.
Plasma proteins like albumen, fibrinogen and globulin are manufactured in the liver.
Storage of blood, vitamins A, K, BI2 and D and mineral salts such as iron' and potassium ions.Detoxification.
Toxic substances ingested e.g. drugs or produced from metabolic reactions in the body are converted to harmless substances in a process called detoxification.
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