KCSE Biology Questions and Answers 

> Joint development of HIV/AIDS vaccine by Kenyan and British scientists.

> The coordinated fight against Severe Acute Respiratory Syndrome involving scientist all over the world.

> The fight to save the ozone layer from depletion through various international agreements such as the Kyoto protocol.

> Management of resources through international treaties such as the CITES (Convention against International Trade on Endangered Species).

Characteristics Of Living Things

Living things share a lot of characteristics in common. These characteristics are discussed below.

a) Nutrition

Nutrition is the process by which living things obtain and assimilate (utilize) nutrients. Living things require nutrients for various purposes; growth, repair of worn out tissues and for provision of energy. Plants manufacture their own food using light energy, carbon (IV) oxide, water and mineral salts through the process of photosynthesis. Conversely, animals feed on already manufactured foods from plants and other animals.

b) Respiration

Respiration is the process by which food substances are chemically broken down to release energy. During respiration, oxygen is used while energy, carbon (IV) oxide and water are released. Respiration occurs in all living cells.

The energy produced in living things is very useful as it enables the living things carry out some of their physiological processes.

The energy is also required for growth and development, movement and repair of worn out tissues.

c) Gaseous Exchange

Gaseous exchange refers to the process by which living things exchange oxygen and carbon (IV) oxide across the respiratory surfaces. Animals always take in air rich in oxygen and give out air rich in carbon (IV) oxide.

Carbon (IV) oxide is a waste product of chemical reactions in the body. Animals require oxygen for respiration. Gaseous exchange, therefore, enables animals obtain oxygen for respiration and get rid of carbon (IV) oxide, a waste product.

Plants, however, require carbon (IV) oxide for photosynthesis during the day. They give away oxygen as a by-product. The plants equally require oxygen for respiration and give away carbon (IV) oxide.

d) Excretion

This is the process by which living things separate and eliminate the waste or harmful materials resulting from chemical reactions Within the cells. These harmful waste products of metabolism maybe toxic to the body if they are left to accumulate in the cells of the living things

e) Growth and Development

Growth refers to an irreversible increase in size and mass while development refers to the irreversible change in complexity of the structure of living things. Growth and development of living things is essential as it enables the living things to attain maximum size that can enable them to perform their functions and roles.

f) Reproduction

This is the process by which living things give rise to new individuals of the same kind. All living things reproduce. Reproduction is essential as it leads to perpetuation of species and it avoids extinction of certain animals and plants.

g) Irritability

This is the ability of living things to perceive (detect) changes in their environment and respond to them appropriately. Living things respond to changes in temperature, humidity, light, presence or absence of certain chemicals.

Response of organisms to these changes is crucial as it enables them to escape from harmful stimuli. Ability to detect changes in the environment also enables organisms to obtain resources in their environment.

h) Movement

Movement refers to change is position (displacement) of a part or parts of an organism. Movement in plants includes folding of leaves, closing of flowers and growing of shoots towards light. The change of position of an entire organism from one position to another is locomotion.

Study questions

a) Motor vehicles move, use energy and produce carbon dioxide and water. Similar characteristics occur in living organisms yet motor vehicles are not classified as living. List the other characteristics of living things that do NOT occur in motor vehicles.

b) Give the name to the study of:

Collection of Specimen

We have defined biology as the study of living things. For effective study, a biologist may have to collect some living things or some parts of living things for observation and analysis. The living things or parts of living things that are used for biological study are called specimens.

Biological studies always take place in laboratories. A laboratory is a building or a room that is designed and equipped for scientific studies.

Collections of living things especially animals may not be very easy. Some of the animals are not easy to catch while some are quite dangerous. Knowledge on proper specimen collection and handling of is very important. We will discuss some of the apparatus used in specimen collection.

a) Sweep net- This is used for catching flying insects.

b) Fish net- This is used for trapping small fish and other small Water animals.

c) Pooter- This is used for sucking small animals from rock surfaces or barks of trees.

d) Bait trap- This is used for attracting and trapping small animals including rats.

e) Pit fall trap- This is used for catching crawling animals.

f) Pair of forceps- This is an apparatus used for picking up small crawling animals e.g. stinging insects.

g) Specimen bottles- These are bottles used for keeping collected specimen. They are of different sizes depending on the size of the specimen being studied.

h) Magnifying lens- This is used to enlarge small objects. A hand lens is a common magnifying lens used in the laboratory. The magnifying power of the hand lenses is always indicated on the lens e. g. X10, X5, X8. The magnifying power of a lens shows how many times the image will be enlarged compared to the object.

How to use a magnifying lens

To use a magnifying lens, place the object to be enlarged on the bench. Hold the magnifying lens on one hand and while closing one eye, move the lens towards the object until the image comes into clear focus.

If a magnifying lens is used to make a drawing of a specimen, the magnification of the drawing will have no relation with the size of the drawing.

The magnification of the drawing can be calculated using the formula shown below.

Drawing magnification: Length of drawing divided by Length of the actual object

The sign of “times” must come before the magnification value e. g. X10, X5, X15 etc.

Precautions During Collection and Observation of Specimen

While collecting specimen for observation, a biologist should play close attention to the following:

Comparison Between Plants and Animals

Plants

Animals

Chapter Two: Classification 1

Introduction

In particular, animals and plants are all living things yet they differ in many aspects. Amongst animals and plants also there exist a lot of differences.

There are millions of different plant and animal types exhibiting a range of differences. This created a need for a classification system of living things to make study of the living organisms easier.

External features of plants used in classification

External features of animals used in classification

Importance of Classification

Historical background of Classification

a) Edible or non edible

b) Flowering or non-flowering

Taxonomic Units of Classification

1. Kingdom

2. Phylum (animals)/division (plants)

3. Class

4. Order

5. Family

6. Genus

7. Species

All living organisms are classified into five major kingdoms:

a) Kingdom Monera- This is composed of microscopic unicellular organisms mainly bacteria e.g amoeba.

b) Kingdom Protoctista- This kingdom is comprised of members who are microscopic. Though, some are large enough to be seen with the naked eyes.

Members of this kingdom include algae and protozoa.

c) Kingdom Fungi- Members of this kingdom comprises the mushrooms, toadstools, moulds and yeast.

d) Kingdom Plantae- This kingdom comprises the moss plant, ferns, maize plants, hibiscus, meru oak tree etc.

e) Kingdom Animalia — Members of this kingdom include the tapeworms, hydra, fishes, human beings, lizards, earthworms etc.

In hierarchy of classification, a kingdom is further divided into several phyla (plural of phylum) or divisions (in plants). Within the phyla or divisions, organisms are further sorted out into groups known as classes based on their similarities and mode of life.

Each class is further subdivided into small groups called orders based on structural similarities. Orders subdivide into families which subdivide into genera (plural for genus).

Genera are then subdivided into smaller units of classification called the species.

Species is the smallest unit of classification whose members share many similarities and can freely interbreed to give rise to fertile or viable offspring.

Members of a particular species can, however, exhibit various differences e. g. differences in skin colour or body forms. Within the species, organisms can further be classified based on the differences in colour or forms.

In humans, this gives the races, in animals the term used is breed while in plants, variety is preferred. In bacteria, the term strain is used to describe the variant forms.

Members of different but very closely related species can breed but the resulting offspring will be sterile (infertile). In particular, a mule is a sterile offspring between a horse and a donkey.

Moving from kingdom to species, it is important to note that the number of organisms in each taxon decreases. The similarities, however, increase as one moves from kingdom to species.

Scientific Naming of Living Organisms

Rules of Binomial Nomenclature

Binomial nomenclature requires that:

a) The first part of the scientific name is that of the genus name which should begin with a capital letter. The second name is that of species. The species name should be written in small letters e. g.

a) Maize- Zea mays

b) Lion- Panthera leo

c) Leopard- Panthera pardus

d) Domestic dog- Canisfamiliaris

e) Human being- Homo sapiens

b) When printed in books and other printed works, the scientific names should be printed in italics. However, in handwritten manuscripts and typed works, the genus and species names should be lined separately.

Printed work- Homo sapiens

c) The specific name is frequently written with the name of the scientist who first adequately described and named the organism e. g. Balanus balanoides Linneaus. d) Scientists must give a latinised name for a newly described animal or plant species where a Latin name is missing e,g.

Aloe kilzfiensis- A type of aloe found in kilifi

Meladogyne kikuyuensis- A nematode found in kikuyu.

Origin of scientific names

Scientific names assigned to organisms can be:

Chapter Three: The Cell

Introduction

The Light Microscope

Magnification=Eyepiece magnification X Objective lens magnification

= 10 X 8

=X80.

Figure 1. The light microscope

Handling and Care of the Microscope

Part of the microscope: Limb

function: supports the body tube and stage

Base:

function: provides firm and steady support to the microscope

Body tube:

function: holds the eyepiece and the revolving nose piece

Coarse adjustment knob:

function: raises or lowers the body tube through longer distances to bring the image into sharper focus

Fine adjustment knob:

function: raises or lowers the body tube through smaller distances to bring the image into sharper focus. it is mostly used with the high power objective lens

Diaphragm:

function: an aperture that regulates the amount of light passing through the condenser to illuminate the specimen

Eye-piece:

function: contains a lens which contributes to the magnification of the specimen under review

Objective lens:

function: bring image into focus and magnifies it.

Mirror:

function: reflects light through the condenser to the object on the stage

Revolving nose piece:

function: holds the objective lenses in place and enables the change from one objective lens to the other

Condenser:

function: concentrates light on the object on stage

Stage:

function: flat platform where specimen on the slide is placed.it has two clips to hold the slide into position

The following rules should be observed when handling the microscope:

> Always use both hands when carrying the microscope. One hand should hold the base to provide support while the other hand holds the limb.

> Never place the microscope too close to the edge of the working bench or table.

> Do not touch the mirror or the lenses with your fingers.

> Dirty lenses should be cleaned using a special soft lens tissue paper or tissue paper moistened with ethanol. The other parts of the microscope may be cleaned using a microscope.

> Do not wet any part of the microscope.

> Make sure the low power objective lens clicks into position in line with the eye piece before and after use.

> After use, always clean and store the microscope in a safe place, free from moisture and dust.

How to use the Microscope

Cell Structures as seen under the Light Microscope

Figure 2 Plant and animal cells as seen under the light microscope

The cell as seen under the Electron Microscope

Figure 4. The plant cell

Structure and Functions of the Cell Organelles

Cell membrane

Cytoplasm

c) Mitochondrion

> Mitochondria are self replicative that is they can divide to form new ones.

Figure 5. The Mitochondrion (Animal)

Figure 6, (generalize(lmage23 mitochondrion Structure)

d) Endoplasmic Reticulum

e) Ribosomes

f) Lysosomes

g)Golgi bodies/Golgi apparatus

1) They package and transport glycoproteins.

2) They are involved in secretion of synthesized proteins and carbohydrates.

3) They manufacture lysosomes.

Note: Golgi bodies are abundant in cells that are active in secretion. For instance pancreatic cells which secrete enzymes and the nerve cells which secrete neurotransmitter substances.

h)Centrioles

i) Chloroplasts

j) Vacuoles

k) Cell wall

1. It gives plant cells their definite shape

2. It provides mechanical support and protection against mechanical injury.

3. The cell wall allows gases, water and other substances to pass through it.

i) Nucleus

Comparison between Plant Cells and Animal Cells

While there exist many similarities between plant and animal cells, there are a number of differences.

Plant cells

Animal cells

Estimation of Cell Size

The light microscope can be used to estimate the size of a cell. Most cells have diameters smaller than a millimeter. Due to this, cell sizes are always measures in smaller units.

These are micrometres and nanometers. These units of measurements are related as shown below.

1 millimeter (mm) = 1000 micrometres (pm).

1 micrometer (pm) = 1000 nanometres (nm).

Procedure in cell size estimation

cell diameter = diameter of the field of view in micrometers divided by number of cells.

Cell Specialization. Tissues. Organs and Organ Systems

Cell Specialization/Cell Differentiation

Tissues

a) Tissue types in animals

1. Epithelial tissue- This is a thin continuous layer of cells for lining and protection of internal and external surfaces.

2. Skeletal muscle- This is a bundle or sheets of elongated cells with fibres that can contract. Its contraction and relaxation brings about movement.

4. Blood tissue- This is a fluid containing red blood cells, white blood cells and platelets.

The main functions of blood tissue are transportation of nutrients and gases as well as protection of the body against infections.

5. Connective tissue- This tissue consists of strong fibres that connects other tissues and organs thereby holding them in position.

b)Tissue types in plants

1. Epidermal tissue- This is a single thin layer of cells covering the outer surfaces. It protects inner tissues of plants from mechanical damage and infection.

2. Palisade tissue- This is a group of cells rich in chloroplasts containing chlorophyll. It has a site for the absorption of light energy and manufacture of food by photosynthesis.

3. Parenchyma tissue- This tissue consists of special thin walled irregularly shaped cells. They form packaging and storage cells.

4.Conducting tissue/Vascular bundle- This tissue consists of xylem and phloem. Xylem conducts water and dissolved mineral salts in a plant while phloem conducts food substances in solution.

Organs

a) Heart- composed of connective, muscle, epithelial and blood tissues.

b) Kidney- Composed of connective, epithelial and muscle tissues

c) Brain- Composed of epithelial, connective tissues

d) Lungs- Composed of epithelial, connective tissues.

a) Roots- composed of epidermal, conducting and parenchyma tissues.

b) Flowers- This is composed of epidermal, conducting tissues.

c) Stem- Composed of conducting, parenchyma, and epidermal tissues and palisade tissues in some cases

d) Leaves- Composed of palisade, conducting and epidermal tissues.

Organ system

This is a group of organs Whose functions are coordinated and synchronized to perform the same function.

Organ systems are more pronounced in animals than in plants

Organ systems in animals include

a) Digestive system composed of organs such as oesophagus, stomach, intestines and their associated glands.

b) Circulatory system composed of the heart, blood vessels (arteries, veins, capillaries). c) Excretory this is composed of kidney, liver, and blood vessels.

d) Respiratory system composed of trachea, bronchus, and lungs.

e) Reproductive system composed of the reproductive organs and associated glands.

f) Nervous systems composed of the brain, spinal cord, eye, ear organs.

Chapter Four: Cell Physiology

Introduction

a) Chloroplasts play a vital role in carbohydrate synthesis.

b) Mitochondrion produces energy required to carry out life processes.

c) Ribosomes manufacture of proteins.

Structure of the membrane

Properties of the cell membrane

a) The cell membrane is semi permeable- The pores that occur on the cell membrane allows the passage of the small size molecules but does not allow the passage of the large sized molecules.

Such a membrane is said to be selectively permeable or semi-permeable. In particular, when a cell is surrounded by a dilute sugar solution, the small sized water molecules will enter the cell but the larger sugar molecules will not pass through the cell membrane.

In contrast, the cell wall is permeable as it allows both sugar and water molecules to pass through it; it has larger pores. This property of selectively permeability enables the cell membrane to select what enters and leaves the cell.

b)The cell membrane is sensitive to changes in temperature and pH- Cell membranes are made up of protein. Proteins are adversely affected by extreme changes in temperature and pH.

Changes in temperature and pH will alter the structure of the cell membrane thereby hindering the normal functioning of the cell membrane. High temperature denatures (destroys) the proteins thereby impairing the functions of the cell membrane.

c)The cell membrane possesses electric charges- The cell membrane has both positive and negative charges. These charges affect the manner in which substances move in and out of the ells. The charges also enable the cell to detect changes in the environment.

Physiological Processes of the Cell membrane

a) Diffusion

b) Osmosis

c) Active transport

Diffusion

Demonstration of the process of diffusion using_potassium manganate (VII)

Requirements: potassium manganate (VII) crystals, glass tubing, 100 cm3 beaker and water.

Procedure

a) Hold the glass tubing vertically in a beaker so that one end of the tubing rests on the bottom of the beaker.

b) Cautiously and quickly drop a crystal of potassium manganate (VII) through the upper opening of the glass tubing.

c) Close the upper hand of the glass tubing with the thumb.

d) Half fill the beaker with water.

e) Carefully withdraw vertically the glass tubing so that the crystal is left undisturbed at the bottom of the beaker.

f) Record your observations for the first 15 minutes.

g) Explain your observations.

Expected observations

Explanation

The Role of Diffusion in Living Organisms

a) In Plants

Diffusion plays an important role in plants in that:

b) In Animals

In animals diffusion plays the following important roles

These include the skin, gills, lungs, tracheal system and the cell membrane (in unicellular organisms). Gaseous exchange at these surfaces occurs through the process of diffusion.

Factors affecting the rate of Diffusion

a) Diffusion gradient

b) Surface area to volume ratio

c) Thickness of membranes and tissues

d) Size of molecules

e)Temperature

Osmosis

Demonstration of Osmosis Using a Visking Tubing

Requirements

5OOcm3 beaker, visking tubing, a piece of thread, glass rod, concentrated sugar solution, 500 cm3 distilled Water.

Procedure

1. Into the beaker, put 350 cm3 of the distilled water.

2. Dip the visking tubing in water to moisten it. Open the visking tubing and tie one end with the thread provided.

3. Half fill the visking tubing with the sugar solution provided and then tie the open end of the tubing. Ensure no sugar solution spills out of the tubing.

4. Immerse the visking tubing into the distilled water in the beaker and suspend it using the glass rod provided.

5. Leave the set up for about 30 minutes.

6. Record your observations.

7.Explain the observations made.

Observations

Explanation

Even though there is a higher concentration of sugar molecules in the visking tubing, they were not able to diffuse out of the visking tubing due to their large molecular sizes. The visking tubing is semi permeable.

Osmosis explained

Osmotic pressure

Osmotic potential

Water Relations in Animals

a) Red blood cell in hypotonic solution e. g. distilled water

When a red blood cell is placed in a hypotonic solution, water will move into the cell through osmosis. The cell will swell and burst. Swelling of red blood cell when placed in a hypotonic solution is referred to as haemolysis. The cell is said to be haemolysed.

b) Red blood cell in hypertonic solution

Water will, therefore, be drawn out of the cell into the hypertonic solution. The cell will shrink and become small. The cell is said to be crenated.

The process by which animal cells shrink and become smaller when placed in hypertonic solutions is referred to as crenation.

c) Red blood cell in isotonic solution

When placed in an isotonic solution, the cell remains unchanged. This is because there will be no net inflow or outflow of water between the cell and the solution.

Note:

This will prevent bursting or shrinking of the cells that would otherwise impair their physiology.

Water Relations in Plants

a) Plant cell in hvpotonic solution e. g. distilled water

Wilting

Role of Osmosis in Organisms

As glucose accumulates in the guard cells, the osmotic pressure of the guard cells increase making them to draw water from adjacent cells through osmosis. When the guard cells become turgid, they bulge outwards leading to opening of the stomata.

Opening of the stomata is crucial as it allows for gaseous exchange in plants. At night, there is no glucose synthesis.

The glucose available in the guard cells is respired on leading to reduction of glucose and consequently reduction in osmotic pressure. The guard cells lose turgidity and close the stomata.

The change in turgor pressure enables the special structures to rapidly close thereby trapping the insects.

Factors Affecting the Rate of Osmosis

Active Transport

Some of these mineral salts cannot be absorbed by the plants through diffusion. A mechanism that would move them into the cells against the concentration gradient will be useful.

Role of active transport in living organisms

Factors affecting the rate of Active Transport

a) Oxygen concentration

Oxygen is required in respiration process that yields energy for active transport. Under low oxygen concentration, the rate of respiration will be low hence there will be production of little energy leading to low rate of active transport. Increase in oxygen concentration translates into a higher energy production leading to high rate of active transport.

b) Change in pH

Change in pH affects the respiratory process which is enzyme controlled. Respiratory enzymes require optimum pH for their efficient activity. Extreme pH conditions will increase lower the rate of active transport since the enzymes controlling respiration Will be denatured.

c) Glucose concentration

Glucose is the chief respiratory substrate. At low glucose concentration, there will b less production of energy leading to decreased rate of active transport. Rate of active transport increases with increase in glucose concentration due to increase in the rate of energy production.

d ) Temperature

Temperature affects the enzyme controlled respiration process. At low temperatures, the enzymes are inactive hence the rate of respiration will be low resulting into low rate of active transport since there will be less production of energy. An increase in temperature increases the rate of respiration since the enzymes become more activated. At temperatures beyond 40 degrees celcius, the enzymes become denatured, respiration stops and so does active transport.

e) Presence of metabolic inhibitors e. g. cyanide.

These are substances which act as metabolic poisons. They stop the rate of respiration leading to production of no energy. Active transport is, thus, stopped.

Nutrition Plants And Animals

Introduction

a) The nutrients are required for growth and development of the living organisms.

b) The nutrients are required for energy provision as they are broken down to release energy.

c) They nutrients are also required for repair of worn out tissues

d) Nutrients are required for synthesis of very vital macromolecules in the body such as hormones and enzymes.

Modes of nutrition

There are two main nutrition modes:

a) Autotrophism mode of nutrition through which living organisms manufacture their own food from simple inorganic substances in the environment such as carbon (IV) oxide, water and mineral ions. Organisms that make their own food through this mode are autotrophs.

b) Heterotrophism mode of nutrition in which living organisms depend on already manufactured food materials from other living organisms. Heterotrophs are the organisms that feed on already manufactured food materials.

Autotrophism

In this mode of nutrition, organisms manufacture their own food from readily available materials in the environment. These organisms use energy to combine carbon (IV) oxide, water and mineral salts in complex reactions to manufacture food substances. Depending on the source of energy used to manufacture the food, there are two types of autotrophism:

a)Chemosynthesis

This is the process whereby some organisms utilize energy derived from chemical reactions in their bodies to manufacture food from simple substances in the environment. This nutrition mode is common in non green plants and some bacteria which lack the sun trapping chlorophyll molecule.

b) Photosynthesis

Importance of Photosynthesis

1. Photosynthesis helps in regulation of carbon (IV) oxide and oxygen gases in the environment.

2. Photosynthesis enables autotrophs make their own food, thus, meet their nutritional requirements.

3. Photosynthesis converts sunlight energy into a form (chemical energy) that can be utilized by other organisms that are unable to manufacture their own food.

External leaf structure

This helps reduce the rate of water loss in such plants. However, the plants in areas of water abundance have broad leaves to enable them lose the excess Water.

a) Cuticle

Functions of the cuticle

a) Being waterproof, it minimizes water loss from the leaf cells to the environment through transpiration and evaporation.

b) It protects the inner leaf tissues from mechanical damage.

c) It prevents entry of pathogenic microorganisms into the leaf.

b) Epidermis

Functions of the epidermis:

a) It protects the leaf from mechanical damage.

b) It also protects the leaf from entry of disease-causing microorganisms.

c) It secretes the cuticle.

Adaptations of the guard cells

c) Palisade mesophyll

d) Spongy mesophyll layer

e) Vascular bundle/tissue

Chloroplast

Adaptations of the leaf to photosynthesis

Raw materials for photosynthesis

Conditions for photosynthesis

Photosynthesis Process

a)Light reaction/Light stage

i) Photolysis of water

Water-- Hydrogen atoms + Oxygen gas

ii) Formation of adenosine triphosphate (ATP)

ADP + P = ATP

b) Dark reaction/Dark stage

Testing for starch in a leaf

Requirements

Procedure

Observations

Factors affecting the rate of photosynthesis

a) Carbon (IV) oxide concentration

At this point, other factors such as light intensity, water and temperature become limiting factors.

b)Light intensity

c)Temperature

Rate of photosynthesis is optimum at (35-40) °C. Beyond 40°C the rate of photosynthesis decreases and eventually stops since the enzymes become denatured.

d) Water

Experiment to investigate the gas produced during photosynthesis

Requirements

Procedure

a) Set up the apparatus as shown in the figure below

b) Place the set up in the sunlight to allow photosynthesis to take place.

c) Leave the set up in the sun until sufficient gas has collected in the test tube.

d) Test the gas collected with a glowing splint.

e) Record your observations.

Note:

1) Carbon (IV) oxide concentration: Carry out the experiment using different amounts of dissolved sodium hydrogen carbonate e. g 5 g, 10g, 15g, 20g and examine the rate at which the gas collects.

2) Light intensity: An artificial light source can be used. Illuminate the plant and vary the distance between the set up and the light source While recording the time it takes for the gas jar to fill or counting the number of bubbles peer unit time.

3) Temperature: carry out the experiment at varying temperatures and record the rate at which the gas collects.

Experiments on factors necessary for photosynthesis

Light

Requirements

Carbon (IV) oxide

Requirements

Procedure

Chemicals Of Life

Carbohydrates

Monosaccharides

Properties of Monosaccharides

Note:

Disaccharides

Properties of Disaccharides

Functions

Polysaccharides

Properties of polysaccharides

Examples of polysaccharides

a) Starch- Made by linking numerous glucose molecules. It is a form in which carbohydrates are stored in plants.

b) Glycogen- Is a storage carbohydrate in liver and muscles of animals. It is broken down to glucose in animals when blood glucose falls.

c) Cellulose- This is a structural polysaccharide in plants. It is a component of the cell wall

d) Chitin- A structural carbohydrate found in cell wall of fungi and arthropod exoskeletons

Functions of polysaccharides

Lipids

Properties of lipids

Functions

Proteins

a) Essential- These are those amino acids that cannot be synthesized by the body systems hence have to be supplied in the diet.

b) Non essential- These are amino acids that can be synthesized by the body mechanisms hence do not need to be supplied in the diet.

a) First class proteins- Contain all essential amino acids

b) Second class proteins- Proteins lack one or more essential amino acids

Protein synthesis

Properties of Proteins

Functions of proteins

a) They are structural compounds of the body. Cell membrane is protein in nature. Hair, nails and hooves are made up of protein keratin.

b) Proteins are broken down to release energy during starvation when all carbohydrate and lipid reserves are depleted.

c) Functional proteins play vital roles in metabolic regulation. Hormones are chemical messengers while enzymes regulate the speed of metabolic reactions.

d) Proteins such as antibodies provide protection to the body against infections

e) Some protein molecules are transport molecules. Haemoglobin molecule plays a crucial role in transportation of respiratory gases.

f) Proteins play a vital role in blood clotting e. g. fibrinogen.

g) Contractile proteins such as actin and myosin bring about movement.

Enzymes

What are enzymes?

Types of enzymes

a) Extracellular: Are produced within the cells but used outside the cells e. g. digestive enzymes.

b) Intracellular: Are enzymes produced and used within the cells e. g. respiratory enzymes.

Importance of Enzymes

Enzyme nomenclature

a).Trivial naming

Examples

b). Use of suffix -ase

Substrates

Processes/Reactions

Hydrolysis .................... ..hydrolase

Reduction ..................... ..reductase

Oxidation ...................... ..oxidase

Mechanism of action of Enzymes

Properties of Enzymes

Factors affecting enzyme activity

a)Temperature

b)pH

c)Enzyme Specificity

d)Substrate Concentration

e) Enzyme Concentration

f) Enzyme co-factors

g) Co-enzymes

Examples

NAD- Nicotine Adenine Dinucleotide.

FAD- Flavine Adenine Dinucleotide.

NADP- Nicotine Adenine Dinucleotide Phosphate.

h) Enzyme inhibitors

1. Competitive

2. Non- competitive

Competitive inhibitors

Non competitive inhibitors

Examples of non competitive inhibitors

Heavy metals (such as lead, mercury, silver), Cyanide, organophosphates such as malathion.

Heterotrophism

Modes of Heterotrophism

a) Parasitism

b) Symbiosis

> Rhizobium and leguminous plants: rhizobium fixes nitrogen for the legume while the bacteria obtains manufactured food from the legumes.

> Lichen: association of fungi (absorbing water and nutrients) and algae (manufacturing food for the association.

> Catalase digesting bacteria and ruminants.

Dentition

Types of Dentition

a) Incisors

a. Canines

b. Premolar and molar

Classes of Holozoic Heterotrophs

a) Herbivores: heterotrophs that exclusively feed on vegetation.

b) Carnivores: heterotrophs exclusively feed on flesh.

c) Omnivores: heterotrophs that feed on both flesh and vegetation.

Dental Formula

a) i-incisors.

b) c-canines.

c) pm-premolars.

d) m-molars.

a) Write down its dental formula.

b) State its mode of feeding.

c) Give a reason.

Herbivores

Carnivores

Dental Diseases

a) Dental Carries

b) Periodontal Diseases

Are of two types:

a) Gingivitis- Characterized by reddening of gums, bleeding and pus in the gums.

b) Pyorrhea- The teeth become loose due to infection of the fibres holding the teeth in the sockets.

Dental Hygiene

Digestion

Digestion in the mouth

a) Sublingual salivary gland; beneath the tongue

b) Sub mandibular gland: under the jaw

c) Parotid gland: Found in the cheeks in front of the ears.

Digestion in the stomach

a) Pepsinogen-This is activated to pepsin which breaks down proteins to peptides.

b) Rennin- Digests caseinogens protein in milk to casein (curd).

e) Hydrochloric acid- This:

d) Mucus- Forms a protective barrier to the stomach wall against corrosion by the HC1. Mucus is secreted by goblet cells in the epithelial membrane of the alimentary canal.

Duodenum

a) Gall bladder in the liver- Secretes bile.

b) Pancreas- Secrete hormones and digestive enzymes.

i. Secretin hormone from the pancreas: Secretin stimulates secretion of pancreatic juice into the duodenum

ii. Cholecystokinin from the duodenal wall: This stimulates secretion of bile from the gall bladder.

a) Pancreatic amylase- This facilitates breakdown of the remaining starch into maltose

b) Trypsin- Digests proteins into peptides.

c) Pancreatic juice-Digests lipids into fatty acids and glycerol

d) Sodium hydrogen carbonate- This:

Provides alkaline medium for activity of the duodenum enzymes.

i. Aid in emulsification (breakdown of fat molecules into tiny fat droplets to increase surface area for digestion).

ii. The salts also provide a suitable alkaline medium for action of the duodenal enzymes.

iii. In addition they neutralize the acidic chyme.

Digestion in the ileum

a) Maltase: speeds up breakdown of maltose to glucose

b) Sucrase: speeds breakdown of sucrose to glucose and fructose

c) Peptidase: speeds breakdown of peptides to amino acids

d) Lipase: speeds breakdown of lipids to fatty acids and glycerol.

e) Lactase: speeds breakdown of lactose to glucose and galactose.

f) Polypeptidase: speeds breakdown of plypeptides into amino acids

Note:

The mucus secreted by the goblet cells lubricates food along the alimentary canal and also protect the canal from being digested by enzymes.

At the end of digestion in the ileum, the resulting watery emulsion is called chyle; it contains soluble end products of digestion ready to be absorbed.

Absorption

a) It is long to provide a large surface area for absorption

b) It has a narrow lumen so as to bring the digested food into close contact with the walls of the ileum for easier absorption

c) It is highly coiled to slow down movement of food thus allowing more time for digestion and absorption of food.

d) The inner surfaces have numerous villi and microvilli to increase surface area for absorption of end products of digestion.

e) The epithelial lining is one cell thick to reduce the distance through which digested food diffuses.

f) Has a dense network of blood capillaries into which digested food materials diffuse to increase transport and thus maintain a steep concentration gradient.

g) Have lacteal vessels in the villi for absorption of fatty acids and glycerol.

Egestion

> This is the process through which the undigested and indigestible food substances are eliminated from the body. Caecum and Appendix

a) Glucose

b) Fatty acids and glycerol

c) Amino acids

Vitamins

a) Fat soluble vitamins- They dissolve in fats and are often stored in the liver. Include Vitamins A, D, E, K.

b) Water soluble vitamins- Dissolve in water. Include vitamins B1, B2, B5, B12 and C.

Vitamin A (retinol)

main food source

Vitamin B1 (thiamine)

main food source

uses in the body

deficiency disease symptoms

Vitamine B2 (riboflavine and nicotinic acid)

main food source

uses in the body

deficiency disease symptoms

Vitamin B5 (pentathonic acid)

main food source

uses in the body

deficiency disease symptoms

main food source

uses in the body

deficiency disease symptoms

Vitamin C (absorbic acid)

main food source

uses in the body

deficiency disease symptoms

Vitamin D (calciferol)

main food source

uses in the body

deficiency disease symptoms

Vitamin E (tosopherol)

main food source

uses in the body

deficiency disease symptoms

Vitamin K (quinone)

main food source

uses in the body

deficiency disease symptoms

Mineral salts

a) Macro-nutrients: Nutrients required in large quantities. These include nitrogen, sulphur, phosphorous, calcium, sodium, iron and magnesium.

b) Micro-nutrients: Nutrients required in small quantities. Include copper, manganese, boron, iodine and cobalt.

Element: Nitrogen

source

function in the body

deficiency symptoms

-

Element: Phosphorous

source

function in the body

deficiency symptoms

Element: Calcium

source

function in the body

deficiency symptoms

Element: Iodine

source

function in the body

deficiency symptoms

Element: Potassium

source

function in the body

deficiency symptoms

Element: Iron

source

function in the body

deficiency symptoms

Element: Sodium

source

function in the body

Element: Chlorine

source

function in the body

Element: Sulphur

source

function in the body

Element: Magnesium

source

function in the body

deficiency symptoms

Roughage

Importance of roughage

a) It rubs against the walls of the alimentary canal stimulating secretion of digestive enzymes and mucus to lubricate the epithelial lining.

b) Roughage enhance peristalsis since as they rub against the walls of the alimentary canal, they stimulate contraction and relaxation of the muscles.

c) Roughage is an absorbent; it extracts water from the alimentary canal making the fecal matter bulky and moist hence can be easily propelled by peristaltic movements. This prevents constipation.

Factors affecting energy requirements in humans

Discuss how the following factors affect energy requirements in humans:

KCSE Biology Questions and Answers Form 2 - Biology Form Two Notes

BIOLOGY NOTES FORM 2

1. a) i) Define transport

ii) Explain the necessity of transport in plants and animals

b) i) Describe the structure and function of root hair

ii) State ways in which the root hairs are adapted to their functions

c) i) Compare the internal structure of a dicotyledonous root and a monocotyledonous root

Monocot root

ii) State the similarities and differences between a dicotyledonous and monocotyledonous root

Similarities

Differences

Monocotyledonous

Dicotyledonous

iii) Compare the internal structure of a monocotyledonous and dicotyledonous stem

Monocotyledonous stem

Dicotyledonous stem

i) Give the similarities and differences between a monocotyledonous and dicotyledonous stem

Similarities

Differences

Monocotyledonous

Dicotyledonous

State the differences between the internal structure of a root and a stem.

c) i) Name the transport structures of a flowering plant

ii) State the ways in which xylem vessels are adapted to their function

a) i) Why do flowering plants need water?

ii) Describe the movement of water from the soil to the leaves of a tall plant

Stem

Leaves

iii) Name the process by which mineral salts enter into a plant

i) Explain the forces that make water and mineral salts move through a plant

ii) Explain the uptake of mineral salts by plants

b) i) What is transpiration?

ii) Name the sites through which transpiration takes place in a plant

iii) State the importance of transpiration to plants

excess transpiration causes wilting

i) Explain the structural factors that affect the rate of transpiration in plants

ii) Explain the environmental factors that affect rate of transpiration in plants

iii) State the structural differences between xylem vessels and sieve tubes

iv) State the adaptations of plants which enable them to reduce water loss

v) State the factors that cause increase in the rate of transpiration from leaves

vi) Explain how drooping of leaves on a hot sunny day is advantageous to a plant

c) Explain how aquatic and terrestrial plants are adapted to deal with problems of transpiration

a. Mesophytes

b. Xerophytes

c. Hydrophytes

d) i) What is translocation

ii) Name the tissue which is responsible for translocation of manufactured food in flowering plants

iii) Name the processes that bring about the translocation of manufactured food

iv) Draw a labeled diagram to represent phloem tissue

ii) State the functions of the labbeled structures cytoplasmic strands

Companion cell

supply nutrients to sieve tube element

Sieve tubes element

iii) name the compounds that are translocated in phloem

Describe an experiment you would carry out in order to demonstrate that phloem transports manufactured food substances in a plant

a. Ringing experiment

ii) Use the radio-active tracers

iii) Collecting exudate from stylets of aphids

e) Describe an experiment you would carry out to demonstrate that xylem transports water

i. Either

ii. OR

2. a) i)List the components of animal transport systems

ii) Distinguish between closed and open circulatory systems

iii) What are the advantages of the closed circulatory system over open circulatory system?

iv) Distinguish between single circulatory system and double circulatory system Single circulatory

b) i) Describe the general layout of the transport system in mammals

ii) Describe the structure and function of the mammalian heart

iii) Explain how the mammalian heart is adapted to performing its functions

the tricuspid valve

iv) Explain why blood leaving the lungs may not be fully oxygenated

e) Describe the structure and functions of the blood vessels

i. Arteries

ii. Capillaries

iii. Veins

b) i) State the ways in which the composition of blood in the pulmonary arterioles differs from that in the pulmonary venules

pulmonary arterioles

pulmonary venules

ii) Give the reasons why pressure of blood is greater in the arterioles than I the veins of mammals

iii) Name the common heart diseases in humans

c) i) State the functions of mammalian blood

ii) Describe how mammalian blood components carry out their functions Plasma

Red blood cells (Erythrocytes)

White blood cells (leucocytes)

Blood platelets (thrombocytes)

iii) State the Ways in which the red blood cells are adapted to their functions

iv) State the structural differences between a red blood cell and a white blood cell.

Red blood cells

White blood cells

v) State the functional differences between a red blood cell and a White blood cell

Red blood cell

White blood cell

How does the heart increase blood flow to some parts of the body during exercise

Explain how oxygen and carbon Iv oxide are transported in the blood

Oxygen

Carbon IV oxide

Most carbon IV oxide is transported from tissues to lungs within the red blood cells and not in the blood plasma. Give the advantages of this mode of transport.

d) i) what is blood clotting?

ii) Name a protein, vitamin, an enzyme and a mineral element involved in blood clotting

iii) describe the blood clotting process

iv) State the role of blood clotting on wounds

v) Explain why blood flowing in blood vessels does not normally clot

iii. Explain the meaning of :

Universal donor

Universal recipient

iii) What is the difference between rhesus positive and Rhesus negative blood samples?

vi) What is blood transfusion?

v) Under what conditions would blood transfusion be necessary in people?

vi) How can low blood volume be brought back to normal?

How may excessive bleeding result in death?

State the precautions that must be taken before blood transfusion

j) i) What is immunity?

ii) Distinguish between natural and acquired immunity

iii) What are allergic reactions?

vi) How does an allergic reaction occur?

ii) State the role of vaccination against certain diseases

3. a) i) What is gaseous exchange?

ii) Why is gaseous exchange important to organisms?

b) i) name the structure used for gaseous exchange by plants

ii) Briefly describe the structure of stomata

iii) State the factors which affect stomatal opening

iv) Name the theories suggesting the mechanism of opening and closing of stomata

v) Describe the mechanism of opening and closing of stomata

i) What is the advantage of having stomata open during daytime and having them closed at night?

c) i) State the ways in which leaves of plants are adapted to gaseous exchange

ii) Describe how gaseous exchange takes place in terrestrial plants

iii) State the ways in which floating leaves of aquatic plants are adapted to gaseous exchange

iv) How is aerenchyma tissue adapted to its function?

v) Explain stomatal distribution in plants of different habitats

d) i) List the types of respiratory surfaces of animals

ii) State the characteristics of respiratory surfaces in animals

iii) Describe gaseous exchange in protozoa

e) i) Make a labeled drawing of a fish gill

ii) How is a fish gill adapted to its function?

iii) Discuss gaseous exchange in bony fish

iv) What is counter-flow system?

vi) What is the advantage of counter-flow system?

f) i) Describe the mechanism of gaseous exchange in terrestrial insects

ii) State how traceholes are adapted to gaseous exchange

g) i) What is breathing?

ii) Name the structures in humans that are used in gaseous exchange

iii) Describe the mechanism of gaseous exchange in a mammal

Breathing in

Breathing out

iv) Explain how mammalian lungs are adapted to gaseous exchange

v) Name the features of alveoli that adapt them to their function

vii) How is the trachea of a mammal suited to its function?

viii) State the advantages of breathing through the nose rather than through the mouth

ix) Give the conditions under which the carbon iv oxide level rises above normal in mammalian blood

x) Explain the physiological changes that occur in the body to lower the carbon iv oxide level back to normal when it rises

h) i)Describe the factors which control the rate of breathing in humans

ii) Name the respirator diseases

4. a) i) Define respiration

ii) Explain the significance of respiration in living organisms

iii) Where does respiration take place?

b) i) Draw and label a mitochondrion

ii) State the most important function of mitochondria

iii) Give the functions of the labeled parts

Outer membrane

Cristae

Matrix

c) Explain the roles of enzymes in respiration

d) i) What is aerobic respiration

ii) Give a word equation for aerobic respiration

iii) What are the end products of aerobic respiration?

e) i) What is anaerobic respiration

ii) What are obligate anaerobes?

iii) What are facultative anaerobes?

iv) State the Word equation representing anaerobic respiration in plants

v) Name the end products of anaerobic respiration in plants

g) i) Give a word equation of anaerobic respiration in animals

Glucose —> lactic acid + energy

ii) Name the end products of respiration in animals when there is insufficient oxygen supply

iii) Why is there a high rate of lactic acid production during exercise?

iv) Why does lactic acid level reduce after exercise?

v) State why accumulation of lactic acid during vigorous exercise lead to an increase in heartbeat

State the economic importance of anaerobic respiration

What is oxygen debt?

h) i) What is respiratory quotient(RQ)?

RQ = volume of CO2 produced

volume of oxygen consumed

ii) Why are respiratory quotient important

iii) Name the respiratory substrates

iv) Why does anaerobic respiration of a given substrate yield a smaller amount of energy than aerobic respiration?

iv) Explain the disadvantages of anaerobic respiration

v) Mention the types of experiments carried out for respiration

5. a) i) Define the following terms

Excretion

Secretion

Egestion

Homeostasis

ii) Explain Why excretion is necessary in plants and animals

-products of excretion are usually harmful while some are toxic

- if allowed to accumulate in the cells they would destroy tissues and interfere with normal metabolism

- They are therefore removed through excretion

b) i) Describe how excretion takes place in green plants

ii) Why do plants lack complex excretory structures like those of animals?

ii) State the excretory products of plants and some of their uses to humans

c) i) Describe excretion in unicellular organisms

-examples are amoeba and paramecium

-They have to remove waste products such as carbon IV oxide and nitrogenous substances e. g urea and ammonia

- These diffuse from the body surface into the surrounding Water

- Diffusion is due to large surface area

ii) List excretory organs and products of mammals

d)i) Draw and label a mammalian skin

ii) Explain how the mammalian skin is adapted to its functions

the skin is made up of dermis and epidermis

Epidermis

Dermis

e) What is the role of lungs in excretion?

f) State the functions of the liver

i. Excretion

ii) Homeostasis

Deamination

g) i) Draw a labeled diagram of mammalian nephrone

ii) Describe how the human kidney functions

iii) State the adaptations of proximal convoluted tubule to its function

iv) Name the common kidney diseases

6. a) i) Why is homeostatic control necessary?

ii) What is internal environment?

b) i) Why is constant body temperature maintained by mammals?

ii) Explain the advantage gained by possessing a constant body temperature

iii) How do mammals regulate body temperature?

iv) Why does body temperature of a healthy person rise up to 37 C on a hot humid day?

v) Name the structures in the human body that detect external temperature changes

vi) State the advantages that organisms with small surface area to volume ratio experience over those with larger

Explain why individuals with smaller sizes require more energy per unit body weight than those with larger sizes.

c) i) What is the meaning of osmoregulation?

ii) State the importance of osmoregulation

iii) State the ways by which desert mammals conserve water fewer glomeruli longer loop of Henle

iv) Explain why some desert animals excrete uric acid rather than Water

v) Explain why eating a meal with too much salt leads to production of a small volume of concentrated urine

vi) Explain how marine fish regulate their osmotic pressure

d) i) What is the biological significance of maintaining a relatively constant sugar level in a human body?

ii) Discuss the role of the following hormones in blood sugar control

Insulin

Glucagon

e) Explain the part played by antidiuretic hormone in homeostasis

f) What is the role of blood clotting in homeostasis?

g) Describe the role of the following hormones in homeostasis

i. Aldosterone

ii. Adrenaline

h) i) Distinguish between diabetes mellitus and diabetes insipidus

ii) How can high blood sugar level in a person be controlled?

iii) Why does glucose not normally appear in urine even though it is filtered in the mammalian Bowman’s capsule?

iv) When is glycogen which is stored in the liver converted into glucose and released into the blood?

v) How would one find out from a sample of urine whether a person is suffering from diabetes mellitus?

KCSE Biology Questions and Answers Form 3 - Biology Form Three Notes

1. a) i) What is meant by the term binomial nomenclature?

ii) State briefly the general principles of classification of living organisms

b) State the main characteristics of the five kingdoms of organisms

i. Monera

ii. Protista(protoctista)

iii. Fungi

iv. Plantae

v. Animalia

c) Describe the economic importance of:

i. Fungi

ii. Bacteria

d) State the main characteristics of the following division of kingdom plantae

i. Bryophyte

ii. Pteridophyta

iii. Spermatophyte

e) Name sub-divisions of spermatophyte and state the characteristics of each class

i. Gymnospermae (cornifers)

ii. Angiospermae (flowering plants)

iii. Name the classes and state characteristics of angiospermae

Dicotyledonae

Monocotyledonae

iv)State the importance of plants

f) i) Give the general characteristics of phylum arthropoda

ii. State the characteristics of the following classes of arthropoda

Diplopoda

Chilopoda

Insecta

Crustacean

Arachnida

iii) State the economic importance of insects

Beneficial effects

Harmful effects

Give the characteristics of the following classes of chordate

Pisces

Amphibian

Reptilia

Aves

Mammalian

a) i) What is a dichotomous key?

i. State the necessity of using a dichotomous key

ii. List the rules followed in constructing a dichotomous key

iv) Describe the procedure of using a dichotomous key. Make a list of major features of the characteristics to be identified

iv You are provided with a specimen kale leaf. Use the dichotomous key below to identify the taxonomic group to which the specimen belongs. Show the steps (number and letter) in the key that you followed to arrive at the identify of the specimen

1 a) Leaf broad....... Go to 2

b) Leaf narrow....... Araicaria

2 a) Leaf parallel vein....... Cynodon

b) Leaf net veined....... Go to 3

3 a) Leaf with one lobe (simple Leaf)....... Go to 4

b) Leaf with many lobes (compound Leaf)....... Grevellea

4 a) Leaf Fleshy....... Kalanchoa

b) Leaf not fleshy....... Go to 5

5 a) Leaf petiole modified to form sheath....... Go to 6

b) Leaf petiole not modified to form sheath....... Brassica

6 a) Leaf purple....... Tradescantia

b) Leaf green....... commelina

Steps 1a, 2b, 3a, 4b, 5b

Identify- Brassica

v) You have been provided with four animals labeled K (mature adult housefly), L (mature adult grasshopper, M(maize flour beetle) and N(Worker termite) use the dichotomous key below to identify the specimens. Write down in the correct order, the steps (number and letter) in the key that you followed to arrive at your answer.

Dichotomous key

1 a) Animal with wings....... Go to 2

b) Animal without wings....... Go to 7

2 a) With two pairs of wings....... Go to 3

b) With one pair of wings....... Diptera

3 a) With membranous wings....... Go to 4

b) Hind pair of membranous wings....... Go to 6

4 a) With long abdomen ....... Odontata

b) Medium sized abdomen....... Go to 5

5 a) Wings with colored scales....... Lepidoptera

b) Wings without scales....... Hymenoptera

6 a) Forewings hard and shell-like....... Coleoptera

b) Forewings hard but not shell-like....... Orthoptera

7 a) Body horizontally flattened....... Isoptera

b) Body laterally flattened....... Symphonopteria

Identify the orders of the various specimen as per the table below

Specimen Order Step followed

K- housefly Diptera 1a, 2b

L- grasshopper Orthoptera 1a, 2a, 3b, 6b

M- beetle Coleoptera 1a, 2a, 3b, 6a

M- termite Isoptera 1b, 7a

2 a) Define the following ecological terms

i. Ecology

ii. Environment

iii. Habitat

iv. Ecological niche

v. Population

vi. Community

vii. Ecosystem

vm. Biosphere

ix. Autecology

x. Synecology

xi. Carrying capacity

xii. Biome

xiii. Biomass

b) i) What are abiotic factors?

ii) Explain how abiotic factors affect living organisms

Wind

Temperature

Light

Humidity

pH

Salinity

Rainfall (Water) or precipitation

Pressure

Mineral salts (trace elements)

c) i) What are biotic factors?

ii) Give examples of biotic factors affecting ecosystems

d) Discuss how the various biotic factors affect living organisms

i. Competition

ii. Predation

iii. Parasitism

iv. Diseases and parasites

v. Symbiotic

and association of organisms of different species where both benefit from the association i.e. there is mutual benefit

vi. Human activities

Saprophytism

e)i) What is nitrogen cycle?

iii) Describe the nitrogen cycle

iii. Nitrogen in the atmosphere cannot be directly utilized by plants. State two ways by which this nitrogen is made available for plant use

f) i) Describe how energy flows from the sun through the various trophic levels in an ecosystem

Give the reasons for loss of energy from one trophic level to another in a food chain

Why are green plants referred to as primary producers in an ecosystem?

vi. Explain the following terms giving suitable examples

Food chain

Food web

Pyramid of numbers

Pyramid of biomass

Account for the decrease of biomass in the successive trophic levels

h) i) Describe the three characteristics of a population growth

Dispersion

Density

ii) Explain how the following methods are used to estimate population of organisms

quadrat method

Line transect

Belt transect

Capture-recapture method

2. a) Describe the adaptations of plants to various habitats

i. Xerophytes

ii. Hyrophytes

iii. Mesophytes

iv. Halophytes

b) 1) What is pollution?

ii) Explain the various human activities that have caused pollution

Causes and effects of air pollution

Control of air pollution

State the causes, effects and methods of controlling and prop roots for support water pollution

Causes and effects

Control of water pollution

iv) State the causes /effects and control methods of soil pollution

Causes and effects

Control of soil pollution

v) Define biological control give suitable examples

vi) What is eutrophication?

i) What are the effects of eutrophication?

vii) What are the effects of eutrophication?

c) Describe the symptoms, mode of transmission and control of cholera, typhoid, malaria and amoebic dysentery in humans

Cholera

causative agent

Transmission

Symptoms

Control

Typhoid

Causative agent

Transmission

Symptoms

Control

Malaria

Causative agent

Transmission

Symptoms

Control

Amoebic dysentery (amoebiasis)

Causative agent

Transmission

Symptoms

Control

d) Discuss Ascaris lumbricoides under the following sub-headings

i. Mode of transmission

ii. Effects of parasite on the host

iii. Adaptations

iv. Control and prevention

e) Discuss schistosoma under the following sub-headings

i. Mode of transmission

ii. Effects on host

iii. Adaptations

Control and prevention

3. a) i) What is reproduction?

ii) Why is reproduction important?

iii) Name the types of reproduction

b) i) What is cell division?

ii) What are chromosomes?

c) i) What is mitosis?

ii) Describe the five stages of mitosis

Interphase

Prophase

Metaphase

Anaphase

Telophase

ii) State the significance of mitosis

d) i) What is meiosis?

ii) State the significance of meiosis

iii) Give a summary of the stages of meioeis

Prophase I

Metaphase I

Anaphase I

Telophase I

Second meiotic division

Prophase II

Metaphase II

Anaphase II

Telophase II

iv) Give the similarities between mitosis and meiosis

v) What are the differences between mitosis and meiosis?

Mitosis

meiosis

d) i) What is asexual reproduction

ii) What is the significance of sexual reproduction in living organisms?

iii) State the advantages of sexual reproduction

iv) Give the disadvantages of sexual reproduction

e) i) What is asexual reproduction?

ii) State the advantages of asexual reproduction

iii) Give the disadvantages of asexual reproduction

iv) Explain how reproduction occurs by the following methods of asexual reproduction

Sporulation

Budding

Binary fission

f) i) What is a flower?

ii) Draw a longitudinal section of a labeled diagram of a flower

iii) Give the functions of the parts of a flower

Receptacle

Calyx

Corolla

Androecium

Gynaecium

iv) What is inflorescence?

v) Explain the meaning of the following terms which describe flowers

Hermaphrodite

Unisexual

Carpelate

Staminate

Dioecious plants

Monoecius plants

Complete flower

Incomplete flower

vi) Explain the meaning of the following types of ovary

Superior Q ovary occurs above other floral parts on the receptacle Inferior (epigynous) Q other floral parts arise above ovary on the receptacle

g) i) What is pollination?

ii) Explain the types of pollination

iii) State the advantages of pollination

iv) List the agents of pollination

v) How are flowers adapted to wind and insect pollination?

Insect pollinated flowers (entomophilus)

Wind pollinated flower (anemophilus)

vi) State the Ways in which plants prevent self-pollination

vii) Give the characteristics that ensure cross pollination takes place in flowering plants

viii) State the advantages of cross pollination

h) i) What is fertilization?

ii) Describe how fertilization takes place in a flower

iii) What is double fertilization?

iv) Name the changes that Occur in a flower after fertilization

b) i) Distinguish between a fruit and a seed

ii) How is a seed formed?

iii) Draw a labeled diagram of a seed

iv) Describe the main parts of a seed

Testa

Hilum

Micropyle

Radicle

Cotyledons

v) Draw a labeled diagram of a fruit

vi) How is a fruit formed?

vii) Explain the importance of fruits in the survival of plants

vii. Distinguish between parthenogenesis and parthenocarpy

iv) state the differences between a seed and a fruit

A Seed

fruit

j. i) What is placentation?

ii) Explain the following types of placentation

Marginal

Basal

Parietal

Axile

Free central placentation

c) i) How are fruits grouped?

Simple fruits

Aggregate fruits

Multiple (compound) fruits

ii) What are succulent fruits?

iii) Give types of juicy fruits

Berry

Drupe

Pome

iv) What are dry fruits?

v) What are dehiscent fruits?

vi) Give types of dehiscent fruits

Legumes

Follicle

Capsule

vii) What are indehiscent fruits?

ii) Give main types of indehiscent fruits

Nut

Achene

d) i) What is seed and fruit dispersal?

ii) Why is dispersal of seeds and fruits necessary?

iii) Explain how seeds and fruits are adapted to various methods of dispersal

Adaptations for wind dispersal

Water dispersal seeds

Animal dispersal seeds

Self dispersal/explosive

5. a) i) Distinguish between external and internal fertilization in animals

ii) State the advantages and disadvantages of external fertilization

Advantages

Disadvantages

iii) State the advantages and disadvantages of internal fertilization

Disadvantages

Advantages

iii) Give a reason why it is necessary for frogs to lay many eggs

iv) Compare external and internal fertilization

b) i) Draw and label the human male reproductive system

ii) Describe how the mammalian male reproductive system is adapted to perform its functions

Penis

Scrotum

Epididymis

Vas deferens

Gametes

Accessory glands

iii) How is the sperm adapted to perform its function?

c) i) Draw and label the human female reproductive system

ii) Describe how the various structures of the human female reproductive system are adapted to their function

Ovaries

Oviducts (Fallopian tube)

Uterus

Cervix

Vagina

Clitoris

iii) Explain how the ovum is adapted to its function

iv) Explain the differences between sperm and ovum

d) i) Explain the process of fertilization

i) Explain the process of implantation

State the functions of umbilical cord

State the role of placenta

e) i) What is gestation period?

ii) Explain the functions of the membranes associated with placenta

Chorion

Amnion

Yolk sac

Allantois

iii) Explain the events that take place to facilitate parturition

iv) State the reasons why later in pregnancy the ovary will b e removed without disturbing the pregnancy

f) i) What are secondary sexual characteristics

ii) State the main secondary changes in

Boys

Girls

iii) Describe the role of hormones in secondary sexual characteristics in

Boys

Follicle stimulation hormone (FSH)

Testosterone

Girls

FHS

LH

Oestrogen

Progesterone

Prolactin

Oxytocin

g) i) What is menstruation?

ii) Describe the role of hormones in the human menstrual cycle

iii) What is menopause?

h) Explain the symptoms, methods of transmitting and prevention (control) of the following sexually transmitted diseases

i) Gonorrhea

ii) Herpes

iii) Syphilis

iv) Trichomoniasis

v) Hepatitis

vi) Candidiasis

vii) HIV/AIDS

6. a) Define the terms

i) Growth

ii) Development

iii) Differentiation

b) i) Differentiate growth in plants and animals

More differences between Plant Growth and Animal Growth

Plant Growth:

1. Growth continues throughout the life of the plant.
2. Here the growth involves increases in the number of parts.
3. Growth take place during definite seasons.
4. Growing pattern is distinct each species.
5. Plant possess well-defined growing regions.
6. A seedling does not resemble an adult plant.
7. A juvenile stage with distinct may be present in the life-history of a plant.
8. Growth is by addition of new parts ahead or around the older ones.

Animal Growth:

1. Growth takes place for definite periods before maturity.
2. Here it does not involve increase in the number of parts.
3. Each species has a distinct season for growth.
4. Growing pattern is absent.
5. They have no such defined growing regions.
6. The young one are identical to adults except in the body size and sexual maturity.
7. A juvenile stage with different morphology does not occur in higher animal.
8. Growth is diffused by all round increases in different organs of the body.

ii) List the processes involved in growth

iv) List the parameters used to measure growth

iv) Name the patterns of growth in organisms

c) i) Name the different types of growth curves

ii) Draw a sigmoid growth curve and explain its different phases/stages

- Slow growth rate at first

Organism adapting to the environment

B-exponential phase

- organisms already adapted

- first growth due to birth rate that is higher than death rate

C- Stationery phase (plateau)

- Birth rate equals death rate (equilibrium)

Lack of nutrients, accumulation of toxic waste products

D-phase of decline

- due to depletion of nutrients, accumulation of toxic wastes, lack of space

- some individuals old hence not reproducing

- death rate higher than birth rate

iii) Draw an intermittent curve and explain the various stages

A-growth

B-no growth

C- moulting/ecdysis

- seen in arthropods

- growth in in arthropods is intermittent(takes place during some time only because their hard cuticles (exoskeleton) does not expand to cause growth

- the cuticle must be shed off first to allow further growth

- the shedding is called ecdysis or moulting

- when moulting has taken place animal grows but growth stops when the exoskeleton hardens again

d) i) What is seed dormancy?

- A state where a viable seed is incapable of germinating when all conditions are favorable.

ii) State the biological importance of seed dormancy

- gives embryo time to reach maturity

- gives time for dispersal

- allows plant to survive adverse conditions

iii) State the factors which cause seed dormancy

Internal factors

- presence of abscisic acid/ABA/ presence of germination inhibitors

- embryo not fully developed

- absence of hormones/enzymes/inactivity of hormones/enzymes/gibberellins/cytokinins

- impermeability of seed coat

External factors

- unsuitable temperature

- absence of light

- lack of oxygen

- lack of oxygen

- lack of water

iv) Give the conditions necessary to break seed dormancy

- scarification/scratching to make seed coat impermeable

- vernalisation/cold treatment in some seeds like wheat

- burning/nicking/expose to heat e.g. wattle seeds

- destruction of germination inhibitors

e) i) What is seed germination?

- process by which a seed develops in a seedling

ii) What is viability

- ability of a seed to germinate

iii) Discuss the various conditions necessary for the germination of seeds

Water

- medium for enzymatic activity

- hydrolysis of food into simpler substances

- medium of transport

- softens the seed

- acts as a solvent

Air

- in form of oxygen

- oxygen is used for respiration/oxidation of food to release energy

Suitable (optimum) temperature

- activates enzymes involved in mobilization of food reserves

Enzymes

-breakdown and subsequent oxidation of food

- conservation of hydrolyzed food products in to new plant tissues

Viability

- only viable seed are able to germinate and grow

iv) Name and describe the types of germination

Epigeal

cotyledons are brought above the ground level during germination due to elongation of the bean seed that elongates to bring about epigeal germination

Hypogeal

- the cotyledons remain below the surface during germination due to elongation of epicotyl e.g maize

vi) Account for the loss in dry weight of cotyledons in a germinating bean seed

vii) Describe the physiological changes that occur in a seed during germination

viii) Explain the biological significance of cotyledons being brought above the ground in epigeal germination

f) i) Distinguish between primary and secondary growth

Primary growth

Secondary growth

ii) What are meristems

iii) State the characteristics of meristematic cells

iv) State the location and function of the following meristematic tissues

Apical meristem

Intercalary meristem

Lateral meristems

v) Describe primary growth

vi) Describe secondary growth in plants

vii) State the significance of secondary growth

g) i) Describe one method which can be used to measure the average growth rate of a single leaf of a plant

Either

- chose/identify a young leaf (just unfolded)

- use the same leaf throughout

- measure (total) length of (whole) leaf

- record

- repeat at regular intervals until no more change occurs/constant length

- average rate of growth is equal to total increase in length divided by the period taken to achieve full length

Average rate of growth = total increase in length divide by period taken to achieve full length

OR

- choose/identify a young leaf(just unfolded)

- use the same leaf throughout

- trace the outline on a graph paper and work out the area

- record

- repeat at regular intervals until regular area

- average rate of growth equals to total increase in area divided by the period of time taken to achieve full area

Average rate of growth = total increase in area divide by period of time taken to achieve final area

i) Describe how the growth of a root can be determined

Materials

- fine thread, marking ink, germinating bean seedlings, blotting paper, ruler marked in millimeters, pins, cork, a boiling tube and moist cotton wool

Procedure

- dry seedlings using blotting paper

- place inside against the ruler marked in mm

- dip the fine thread in waterproof ink

- mark the radicle at equal intervals

- pin the seedling to the cork

- suspend the seedling into the boiling tube containing moist cotton wool

- allow the seedling to grow for two days/some time observe the intervals with the marks

- record your observations the Widest intervals are found in the region just behind the tip indicating/showing region of greatest growth

iii) A boy hammered a nail in the bark of a tree at a height of 1.5 metres above the ground Four years later, the nail was found at the same height although the tree had grown 3 meters taller. Explain the above observation

The nail was hammered at a point where vertical growth had stopped/further growth was confined to increase in width/diameter.

Vertical growth is confined to tips/apex/vertical apical meristem

h) i) Describe the role of hormones in growth and development of plants

Cytokinnins (Kinnins/Kinnetin/Zeatin)

- breaks dormancy

- promotes flowering

- promotes cell division

- stabilizes protein and chlorophyll

- promotes root formation on a shoot

- low concentration encourages leaf senses

- normal concentration increases cell enlargement in leaves

- stimulates lateral bud development

Ethylene (ethynel C2H4)

- accelerates ripening in fruits

- encourages fruit fall/leaf fall

- induces thickening in stern/inhibits stem elongation

- promotes flowering (in pineapples)

- promotes germination in certain seeds

Abscisic acid (ABA) abscisin hormone/dormin)

- causes bud dormancy

- encourages fruit/leaf fall

- high concentration causes closing of stomata

- causes seed dormancy

- inhibits cell elongation

Traumatin

- heals wounds by callous formation

Florigen

- promotes flowering

ii) State the applications of plant hormones in agriculture

- induce root growth in stem cuttings

- selective weed killers

- encourage sprouting of lateral buds

- breaking seed dormancy

- induce parthenocarpy

- accelerate ripening of fruits

- promote flowering

- cause dormancy

iii) Explain apical dominance

- a phenomenon whereby production of auxins by a growing apical bud of a shoot inhibits growth of lateral buds

- this inhibition is due to high concentration of auxins (indoleacetic acid/IAA) in apical bud

- removal of terminal/apical bud causes development and sprouting of several buds which later develop into branches

- applied in pruning coffee, tea and hedges

- this leads to more yield

iv) Describe the role of hormones in the growth and development of animal

somatotrophin (growth hormones)

- from anterior pituitary

- promotes cell division

- overproduction causes gigantism

- underproduction causes dwarfism

Thyroxine

- promotes growth and metamorphosis

- underproduction leads to a child becoming a cretin (mentally retarted)

Androgens

- in males

- growth of male reproductive organs

Oestrogen

- in females

- growth of female reproductive organs

Ecdysone

- in arthropods

- moulting (ecdysis)

t) i) What is metamorphosis?

- change in form during which there are changes in structure and function in body of organism

- prepares organism for life in a different habitat

ii) Explain complete metamorphosis

radical changes in the body during the life cycle of an organism

called holometabolous development

example is egg larva pupa adult (imago)

occurs in animals such as butterfly and bee

iii) What is the significance of each of the four stages in complete metamorphosis?

Larval stage

- feeding takes place

- larva is quite different from adult

- larva sheds its cuticle (exoskeleton) several times to emerge as pupa

- dispersal stage avoids overcrowding

Pupa

- enclosed in a case called puparium (cocoon)

- no feeding

- organ formation takes place

Adult

- emerges from puparium

- reproductive stage of the life cycle

iv) Describe incomplete metamorphosis

- called hemimetabolous development

- changes are gradual

- eggs develop into nymphs which develop into adults

- nymph resembles adult but are sexually immature

- a nymph moults several times as some parts develop before it becomes an adult

- stage of development between one moult and another is called instar

- occurs in insects such as locust and cockroach

v) Name the hormones that control metamorphosis in insects

- brain hormone responsible for moulting because it simulates production of ecdyson (moulting hormone)

- ecdysone(moulting hormone) causes moulting

- juvenile hormone causes moulting in larvae

vi) State the advantages of metamorphosis in the life of insects

- the adult and larvae exploit different niches

- do not compete for food

- pupa cam survive adverse pupa can survive adverse conditions eg-feeding stage

- dispersal prevents overcrowding

KCSE Biology Questions and Answers Form 4 - Biology Form Four Notes

Biology Form 4 Notes

a) i) Define the term genetics

ii) List some characteristics which are inherited

iii)State the importance of genetics

b) i) Explain the meaning of the following terms

Heredity

Trait

Gene

Allele

Chromosomes

DNA

ii) List the types of chromosomes

c) i) What is variation?

ii) State the causes of variation in organisms

iii) Name the types of variation

iv) Explain the following terms

Acquired characteristics

Genotype

Phenotype

Dominant gene (character)

Recessive gene

Homozygous

Heterozygous

F1 and F2

d) i) Explain Mendels first law of inheritance

ii) Give an example of this law

iii) What is monohybrid inheritance?

i) What is complete dominance?

ii) Give an example of co dominance

In a certain plant species, some individual plants may have only white, red or pink flowers. In an experiment a plant with white flowers was crossed with a parent with red flowers. Show results of Fl generation. Use letter R for red gene and W for white gene.

If the plants form F1 were selfed, work out the phenotype ratio for the F2 generation Phenotypic ratio 1 red:2 pink: 1 white

Genotypic ratio 1:2:1

f) i) What is a test cross?

OR

ii) State the importance of a test cross in genetics

iii) What are multiple alleles?

example is blood group which can be determined by any two of three alleles i.e. A,B and O

iv) Explain the inheritance of ABO blood groups

ii) Explain the inheritance of Rhesus factor (Rh) in human beings

people who have Rh antigen are Rh(+ve) while those without Rh antigen in their blood are Rh(-ve)

recessive the result is as shown below

Let the gene for dominant Rh factor be R while gene for recessive be r

iii) How is sex determined in human beings .

chromosome

g) i) What does the term linkage mean?

- These are genes which occur together on a chromosome and are passed to offspring without being separated ii) Define the term sex-linked genes

iii) What is meant by the term sex linkage?

iv) Name the sex-linked traits in humans

v) Give an example of a sex linked trait in humans on:

Y Chromosome

X Chromosome

vi) In humans red-green colour blindness is caused by a recessive gene C, which is sex- linked. A normal man married to a carrier Woman transmits the trait to his children. Show the possible genotypes of the children.

Let C represent the gene for normal colour vision (dominant)

Let c represent the gene for colour blindness

Parental phenotype Norman man x carrier woman

iv) State the importance of sex linkage

possible to determine sex of day old chicks

v) Haemophilia is due to a recessive gene. The gene is sex-linked and located on the x chromosome. The figure below shows sworn offspring from phenotypically normal parents

What are the parental genotypes?

Work out the genotypes of the offspring

h) i) What is mutation?

ii) Describe how mutations arise

iii)State the factors that may cause mutation

Radiations Effects

X-rays gene/chromosome alteration

Ultra violet rays structural distortion of DNA

Chemicals Effect

colchicines prevents spindle formation

Cyclamate chromosome aberrations

Mustard gas chromosomes aberrations

Nitrous acid adenine in DNA is deaminated so behaves like guanine

Acridone orange addition and removal of bases of DNA

Formaldehyde

iv) State the characteristics of mutations

v) Explain chromosomal mutation

- Change in nature, structure or number of chromosomes

vi) Explain how the following types of chromosomal mutations occur

Duplication

Inversion

Deletion

Translocation

Non-disjuntion

Polyploidy

vii) What are gene mutations?

i) Explain how the following occur during gene mutation

Deletion

Inversion

Insertion

Substitution

ii) Name the disorders in humans caused by gene mutation

I. State the practical applications of genetics

i. Breeding programmes (research)

ii. Genetic engineering

iii. Law

- legal questions of paternity knowledge of blood groups or blood transfusion

iv) Genetic counseling

v) Others

- Pre-sex determination

Understanding human evolution and origin of other species.

2. a) i) Explain the meaning of evolution

ii) Differentiate organic evolution from chemical evolution as theories of origin of life

iii) What is special creation?

b) Discuss the various kinds of evidence for evolution

i) Fossils

ii) Comparative anatomy

iii) Comparative embryology

iii) Comparative serology/physiology

iv) Geographical distribution

as a result of continental drift isolation of organisms occurred bring about different patterns of evolution

Examples

vi) Cell biology (cytology)

c) i) State the evolutionary characteristics that adopt human beings to the environment

- Brain

- Eyes

- Upright posture/bipedal locomotion

- prehensible arm/hand

- Speech

ii) State the ways in which Homo sapiens differs from Homo habilis

d) i) Explain Larmarck’s theory of evolution

- Inheritance of acquired characteristics/environment induces production of a favorable trait which is then inherited

ii) Explain why Lamarck’s theory of evolution is not accepted by biologists today

- evidence does not support Lamarck’s theory

- acquired characteristics are not inherited/inherited characteristics are found in reproductive cells only

iii) Explain Darwin’s theory of evolution

- inheritance of genetically acquired characteristics

- a character happens to appear spontaneously which gives advantage to an organism therefore adapted then inherited through natural selection

e) i) What is natural selection?

- Organisms with certain characteristics are favoured by the environment

Such organisms tend to survive and produce viable offspring

Others not favored are eliminated from subsequent generations

ii) With examples, explain how natural selection takes place

- organism with certain characteristics are favored by their environment

- such organisms tend to survive and produce viable offspring

- others not favored are eliminated from subsequent generations

- as the environmental conditions change the survival value of a character may alter with time so that characteristics which were favored may no longer have advantage and other characters may then become favorable

- if a favorable character is inherited, then offspring produce generations which are better adapted to survive in a population

- more offspring are produced than can survive which results in struggle for survival - the fittest survive

iii) State the advantages of natural selection to organisms

- assist to eliminate disadvantageous characteristics/perpetuates advantageous characteristics

- allows better adapted organisms to survive adverse changes in the environment/less adapted organisms are eliminated

iv) State the ways in which sexual reproduction is important in the evolution of plants and animals

- brings about useful variations/desirable characters

- variations make offspring better adapted for survival/more resistant to diseases

- may lead to origin of new species

v) Explain the significance of mutation in evolution

- Mutation bring about variation which can be inherited

- Some of these variations are advantageous to the organism

- Others are disadvantageous

- The advantageous variations favour the organism to compete better in the struggle for survival

- This results into a more adapted organism to its environment or new species/varieties

- Those with disadvantageous characters will be discriminated against therefore eliminated from the population/death/perish

vi) Plain why it is only mutations in genes of gametes that influence evolution

- gametes form the new offspring

vii) How would you prove that evolution is still taking place?

- resistance of organism to antibiotics, pesticides and drugs

- new varieties of bacteria are resistant to certain antibiotics such as penicillin

- houseflies and mosquitoes are resistant to DDT

vii) Explain why some bacteria develop resistance to a drug after they have bee subjected to it for some time

- bacteria mutates/develops a new strain/chemical composition is altered hence is able to produce enzymes/chemicals which degrade the drug rendering it non-susceptible to the drug

- the new strain is favoured by selection pressure natural selection

f) How has industrial melaninism i.e. peppered moth contributed towards the mechanism of evolution

- This is an example of natural selection

- The peppered moth exists in two distinct forms, the speckled white form (normal form) and a melanic form (the black/dark)

- They usually rest on leaves and barks of trees that offer camouflage for protection

- Originally the “speckled white” form predominated the unpolluted area of England

- This colouration offered protection against predatory birds

- Due to industrial pollution tree barks have blackened with soot

- The white form underwent mutation

- A black variety/mutant emerged suddenly by mutation

- It had selective advantage over the white forms that were predated upon in the industrial areas

- The speckled white form is abundant in areas without soot/smoke

3. a) i) Define irritability, stimulus and response irritability

-also called sensitivity

- Responsiveness to change in environment

Stimulus

A change in the environment of organism which causes change in organism’s activity

Response

- change in activity of an organism caused by a stimulus

ii) State importance of irritability to living organisms

- Adjusting to environmental conditions. Sensitive/defect/responding

iii) List the examples of external stimuli to organisms

- air/oxygen (aero)

- light(photo)

- osmotic pressure (osmo)

- current (Rheo)

- chemical concentration (chemo)

- \water/moisture (hydro)

- Touch/contact (hapto/thigmo)

- Gravity/soil (geo)

- Temperature (thermo)

b) i) What are tactic responses?

- response in which whole organism or its motile parts move e. g. gamete

ii) What causes tactic responses?

- caused by unidirectional stimulus

- usually doesn’t involve growth

- response is either positive or negative

- named according to source of stimulus

- e.g phototaxis, aerotaxis, chemotaxis

iii) State the importance of tactic response to:

Members of kingdom protista

- move towards favorable environment/move away from unfavorable environment

- move towards their prey/food

Microscopic plants

- escape injurious stimuli/seek favorable habitats

iv) Name the type of response exhibited by:

Euglena when they swim towards the source of light

- phototaxis

- sperms when they swim towards the ovum

- chemotaxis

v) State the advantages of tactic responses to organisms

- to avoid unfavorable environment/injurious stimuli

- escape from predators

- to seek favorable environment

- to seek for food/prey

c) i) Define the term tropism

- growth movement of plants in response to external unilateral/unidirectional stimuli

ii) Explain the various types of tropism in plants

Phototropism

- growth movements of plant shoots in response to unilateral sources of light

- the tip of the shoots produce auxins down the shoot

- light causes auxins to migrate to outer side/darker side causing growth on the side away from light hence growth curvature towards source of light roots are negatively phototrophic

Geotropism

- response of roots/pans of a plant to the direction of force of gravity

- auxins grow towards the direction of force of gravity causing positive geotropism in roots while shoot grows away from force of gravity (negatively geotrophic)

Thimotropism/Haptotropism

- growth response of plant when in contact with an object

- contact with support causes migration of auxins to outer side causing faster growth on the side away from contact surface

- this causes tendrils/stem to twin around a support

Hydrotropism

- growth movement of roots in response to unilateral source of water/moisture

- the root grows towards the source of water/ positively hydrotropic while leaves are negatively hydrotropic

chemostropism

- growth movement of parts of plant to unilateral source of chemicals

- the chemicals form a gradient between two regions e.g. pollen tube growing towards the ovary through the style

iii) State the ways in which tropisms are important to plants

- expose leaves/shoots in positions for maximum absorption of sunlight for photosynthesis

- enables roots of plants to seek/look/search for water

- enables plant stems/tendrils to obtain mechanical support especially those that lack woody stems.

- enables roots to grow deep into the soil for anchorage

- enables pollen tube grow to embryo sac to facilitate fertilization

iv) Explain the differences between tropic and tactic responses

Tropism

-growth curvature in response

-slow

-influenced by hormones

Taxes

-locomotory response

-fast

-external influence

d) The diagram below represents growing seedlings which were subjected to unilateral light at the beginning of an experiment

i) State the results of P, Q and R after S days

- P will bend/grow towards light

- Q will remain straight/have little or no growth

- R will remain/grow straight/grow upwards

ii) Account for your results in (i) above

P- Growth substance/growth hormone/IAA/auxin are produced by the stem tip

- they move (downwards and get distributed) to the side away from light where they cause rapid/more growth/cell division/elongation that results in bending

Q- Source of auxin has been removed

R- The auxins cannot be affected by light because the tip has been covered

iii) If the tin foil were removed from the tip of seedling R, what results would be observed after two days

- it will bend/grow towards light

iv) State the expected results after 3 day is if the box were removed

- all seedlings will grow straight/upwards

e) In an experiment to investigate a certain aspect of plant response, a seedling was placed horizontally as shown in diagram I below. After seven days the appearance of the seedling was as shown in diagram 2

Account for the curvature of the shoot and root after the seven days

i) Shoot

- auxins accumulate on the lower side of the seedling due to gravity

- high concentration of auxins in shoot stimulates faster growth causing more elongation on the lower side than the upper side hence curvature occurs upwards

ii) Root

- the high concentration of auxins inhibits growth hence the upper side with less auxins grows faster than the lower side therefore the curvature occurs downwards

f) What is etiolation?

- phenomenon exhibited by plants when grown in darkness

- such plants are pale yellow due to absence of chlorophyll, have small leaves, long stems/hypocotyle and slender stems

- plants exhibit etiolation to reach light/obtain light

- this is a survival response

4. a) i) What is coordination in animals

- The linking together of all physiological activities that occur in the body so that they take place at the night time and in the correct place

ii) Name the main systems for coordination in animals

- Nervous system/sensory system

- Endocrine (hormonal system)

iii) List the components of the mammalian sensory system

- Central nervous system (CNS), brain & spinal cord

- Peripheral nervous system (PNS) cranial and spinal nerves

- Sense organs

- Autonomic nervous system (ANS) nerve fibers and ganglia

iv).Explain the terms receptors, conductors and effectors

- Receptors are structures that detect stimuli i.e. sense organs

- Conductors transmit impulses from receptors to effectors e. g. neurons

- Effectors are the responding parts e.g. muscles, glands

v) What are the functions of the central nervous system?

- provides a fast means of communication between receptors and effectors

- coordinates the activities of the body

vi) State the differences between somatic and autonomic systems of peripheral nervous system

- Somatic is concerned with controlling the conscious or voluntary actions of the body i.e. skin, bones, joints and skeletal muscles

- the autonomic (automatic) nervous system controls involuntary actions of internal organs, digestive system, blood vessels, cardiac muscles and glandular products.

b) i) What is a neurone?

ii) Name the parts of a typical neurone and state the functions of each part

i) Describe the structure and function of a motor neurone

ii) Describe the structure and of sensory neurone

iii) State structural differences between motor and sensory neurons

iv) Describe the structure and function of a relay neurone

c) State the function of the major parts of the human brain

i) Cerebrum

ii) Mid brain

i) Hind brain

a) i) What is reflex action?

ii) Describe a reflex action that will lead to the Withdrawal of a hand from a hot object

iii) Explain how an impulse is transmitted across the synapse (gap)

ii) Briefly describe the transmission of a nervous impulse across a neuro-muscular junction

iii) What are the functions of a synapse?

b) i) What is a conditioned reflex?

ii) Explain a conditioned reflex

iii) Compare a simple reflex action with a conditioned reflex

c) i) What are endocrine glands?

ii) State the functions of hormones in animals

iii) Name the main endocrine glands, their secretions and functions in the human body

Hormone:

Thyroxine

Function:

increases the rate of metabolism

Hormone:

Parathyroid hormone

Function:

regulates calcium and phosphate levels

Hormone:

growth hormone

Function:

regulates growth of the body

gonadotrophic hormone

Function:

stimulates the growth of male and female organs

lactogenic hormone (prolactine)

Function:

stimulates secretion of milk after child birth

thyrotropic hormone( TSH)

Function:

proper functioning of thyroid glands/thyroxine production

adrenocorthicotropic hormone (ACTH)

Function:

stimulate release of adrenal cortex hormone

oxytocine hormone

Function:

regulates blood pressure

stimulates smooth muscles

stimulates contraction of uterus during child birth

aids flow of milk from mammary glands

follicle stimulating hormone (FSH)

Function:

causes maturition of egg in females

stimulates sperm production in male

Vasopressin (ADH) antidiuretic hormone

Function:

regulates water balance by kidney

adrenaline (epinephrine hormone)

Function:

for emergency

prepares body to cope up with stress

aldosterone hormone

Function:

maintain balance of salt and water in blood

cortisone hormone

Function:

break down the stored proteins to amino acids

aids in the break down of adipose tissue

regulates sugar levels in the blood

prevents inflammation

sex hormone

Function:

supplements sex hormones produced by gonads

promotes development of sexual characteristics

Hormone:

insulin

Function:

regulates levels of sugar in blood

enables liver to store sugars

glucagon

Function:

regulates levels of sugar in blood