KCSE-Biology

Q1. Explain the meaning of each of the following terms.

Cell - Basic unit of organization in an organism
Tissue these are cells of a particular type grouped together to perform a certain function

Q2. State the importance of nutrition

For respiration to get energy
For growth
For development
To repair and replace worn out and damaged tissues

Q3. State the importance of photosynthesis

Formation of sugars/glucose which is a source of energy
Purification of air
storage of energy to be used later in respiration

Q4. Discuss how the human ear is adapted to its functions. (20mks)

Pinna a funnel shaped structure / made of skins and cartilage; receive sound waves and direct it to ear tube/ external auditory meatus.
External auditory meatus, a canal lined with hair and wax secreting cells to allow passage of sound waves of eardrum/ middle ear (hair and wax) to trap dust particle.
Wax maintains the flexibility of the eardrum.
The tympanum/eardrum is a thin, sheet-like structure to receive sound waves, vibrate and pass vibration to ossicles.
Ear ossicles (malleus tiny bones incus stapes) act as lever system which amplifies and transmit vibration to the oval window.
The eustachian tube is a hollow structure that connects the middle ear nasal cavity and equalizes pressure between inside and outside of the eardrum/ balancing.
The inner ear has interconnected canals filled with fluids that conduct vibration from middle ear hearing has semi-circular canals filled with fluids that suspend hair cells in the ampullar for balancing.
Fluids also absorb mechanical shock to protect the delicate sensory structures.
The cochlea is coiled to increase surface area for sound reception.
The cochlea has an auditory nerve that transmits sound impulses to the brain for interpretation.

Q5. Explain how comparative embryology is evidence for organic evolution. (2mks)

is comparing formation and development of embryos; this study shows that vertebrate embryos have similar morphological features during their early development and it is impossible to tell them apart; this indicates a common ancestry; some features include a single circulatory system, segmented myotomes gill slits/ visceral clefts, notochord and tail.

Q6. Describe the structure and functions of the various parts of the human ear. (18mks)

Pinna- its funnel shaped to collect and direct sound waves into the auditory meatus.
External auditory meatus- concentrates or direct sound waves to the tympanic membrane which vibrates; has hair that prevents entry of dust particles or any foreign materials to avoid obstruction of sound waves
Ear ossicles- they are joined firmly to one another by ligaments/muscles to transmit vibration across the middle ear
The oval window-thin membrane vibrates effectively, and smaller in size than the tympanic membrane; and transmits them to the fluids in the cochlea.
Eustachian tube –opens at the pharynx to communicate to the mouth cavity; to equalize the air pressure in the middle ear with the atmospheric air pressure
Round window- is a thin membrane that stops disturbance/ displacement /distortion of cochlea fluid; by pushing towards the middle ear for vibration to die/ diffuse off.
Cochlea – has fluids perilymph and endolymph; that distort/displace sensory hair thereby generating a nerve impulse.

Q7. Describe the mechanism of gaseous exchange in a mammal.(16mks)

Inhalation(breathing in )

external intercostal muscle contract; while internal intercostal muscles relax; this cause rising of the ribcage upward and outwards; muscle of the diaphragm contract hence diaphragm flattens; the volume of the thoracic increases; and pressure decreases than the atmospheric pressure; the higher air pressure in the atmosphere forces air into the lungs; and inflate

Exhalation(breathing out)

the intercostal muscles relax; while the internal intercostal contract; this causes the ribcage dome-shape; this makes the volume of the thoracic cavity to decrease; while pressure increase compared to the atmospheric pressure; higher pressure in the thoracic cavity forces air out of the lungs and the lungs deflate.

Q8. Explain the mechanism of stomatal opening in plants. (4mks)

during the day photosynthesis takes place in the guard cell; forming sugar/ glucose; glucose is osmotically active hence guard cells draw water by osmosis from adjacent epidermal cells; guard cells become turgid and bulge outwards; thin outer walls expand faster hence thick inner wall curve; causing the stomata aperture to open

Q9. Explain the role of human skin in:

Thermo-regulation.(16mks)

when the temperature is low, the erector pili muscles contract; marking the hair follicles to stand erect; the hair follicles trap a layer of hair; between them which reduces heat loss due to poor heat conduction

the skin has a sweat gland which secretes sweat; when the temperature is high water from the sweat evaporates

blood vessels vasoconstrict; less blood flows close to the skin surface; hence less heat is lost to the environment

When the temperature is low no sweat is produced.

When the temperature is high the blood vessels vasodilate and this encourages loss and more heat; as more flow close to the skin surface

Protection (4mks)

the skin has a cornified layer made of dead cells which protect the entry of bacteria and inner tissues from mechanical damage; the sebaceous gland, secrete sebum which has antiseptic properties hence protects the body from bacteria. The skin has melanin pigments which protect the body from harmful UV rays

Q10. State the structural adaptation of the insects' tracheal system. (10mks)

spiracles are openings through which gases(oxygen and carbon (14) oxide) enter or exit the tracheal system;/ventilate;
vales on the spiracles; control opening and closing of spiracles;
tracheoles have a moist lining that dissolves respiratory gases before they diffuse
tracheoles have a thin epithelium; to shorten distance over which gases diffuse;
the trachea is highly branched into tracheoles; to increase surface area for gaseous exchange;
hair on the spiracles traps dust/foreign particles and prevent their entry into the tracheal system

Q11. Describe how various hormones influence the menstrual cycle. (10mks)

Follicle stimulating hormone;

Stimulate the development of Graafian follicles in the ovary;

Stimulates the ovarian tissues to secrete oestrogen

Oestrogen;

Initiates/ stimulates the healing and repair of the uterine lining after menstruation

High levels stimulate the pituitary gland to secrete luteinizing hormone;

Luteinizing hormone

Stimulates maturation of Graafian follicle;

Stimulates the rapture of mature Graafian follicle to release the ovum during ovulation.

Stimulates the remains of Graafian follicle to from corpus luteum/yellow body;

Stimulates the corpus luteum to secrete progesterone;

Progesterone

Promotes the thickening of the uterine lining in preparation for implantation;

Inhibit secretion of follicle stimulating hormone and luteinizing hormone

Q12. Explain the process of formation and removal of urea in the human body.(20mks)

Excess amino acid are deaminated in the liver; the amino acid group is reduced to form ammonia; the carboxyl group is oxidized to release energy, or converted glycogen and store in the liver; can also be converted to fats; the ammonia produced is converted to urea; urea form in the liver is shed into the bloodstream; it is transported through the blood plasma;; out of the liver through the hepatic vein; into inferior vena cava to right auricle; through the tricuspid valve into right ventricle; through the pulmonary artery into lungs; blood carrying urea flows out of the lungs through the pulmonary vein to the left auricle; through bicuspid valve into left ventricle; out through aorta; to dorsal aorta then into renal artery which branch into afferent arteriole to glomerulus; into bowman’s capsule; proximal convoluted tubules loop of henle; distal convoluted tubule; enter into the collection dust which drains urea in urinary bladder; the through urethra excreted as urine;

Q13. Describe the adaptation of floating water lily leaf its photosynthetic function.(10mks)

Broad/flat lamina/ large; to provide a large surface for carbon (IV) oxide; and light absorption
Thin leaf to allow light/ carbon (IV) oxide to pass through a short distance
Presences of numerous/ many stomata; on the upper epidermis, ensuring efficient diffusion of carbon (IV) oxide
Cuticle/epidermis translucent; to allow penetration of light to palisade cells/photosynthetic cell
Numerous aerenchyma cells; for buoyancy; to reach light and carbon (IV) oxide
Has an extensive network of veins; conducting water and mineral salts; to the photosynthetic cells

Q14. Describe the following stages of photosynthesis

Light stage

Occurs in the grana/ granum containing chlorophyll which traps/ absorbs light energy
Energy splits water molecules/ photolysis into hydrogen ion and hydroxyl ion
Oxygen gas removed through stomata/ respired
Light energy used in ATP formation; dark stage / carbon (IV) oxide fixation
Simple sugars formed respired/ oxidized or converted to storable form
ATP energy from light stage/ photolysis used to catalyze the reaction

Q15. Discuss how the mammalian heart is adapted to its function( 20mks)

The heart has atrioventricular valves and semi lunar valves; allowing blood flow in one direction only and prevent backflow
Valves have non-elastic chordae tendoneae preventing atrioventricular valves from turning inside out into auricles during ventricular systole
Has thick muscular walls which contract to pump and push blood
Made of cardiac muscles which are myogenic
The heart served by vagus sympathetic nerves which regulate the rate of heartbeats depending on the body’s physiological/ requirements
Cardiac muscle served by coronary artery and coronary vein for the supply of nutrients O2 and removal of waste respectively
Has specialized interconnected cardiac Purkinje fibres which spread the wave of excitation throughout the heart muscles
Has four chambers that hold the blood briefly before it is pumped to the lungs and the rest of the body
Has a septum wall preventing oxygenated blood on the left side of the heart from mixing with deoxygenated blood on the right side
Has vena cava and pulmonary vein that transport blood to the heart auricles from the rest of the body and lungs respectively
The pulmonary artery and aorta transport blood away from the heart ventricles to the lungs and rest of the body respectively
Entire heart is enclosed by a tough double layered protective sac, the pericardium, preventing it from overstretching as it pumps

Q16. Discuss the various evidences which show that evolution has taken place (20mks)

Comparative anatomy/ taxonomy

Members of a phylum/ group show similarities; organisms have similar structures / similar organs performing the same functions

Analogous structure / different structure with different organs performing same functions/ showing convergent evolution

Fossil records/ paleontology

These are remains of organisms preserved in naturally occurring materials for many years; show morphological changes of organisms over a long period of time

Comparative embryology

Vertebrates embryos are similar; suggesting that the organisms have a common origin/ ancestry

Geographical distribution

Present continents are thought to have been a large landmass joined together as a result of continental drift; isolation occurred bringing about a different pattern of evolution

Cell biology/ cytological

Occurrence of cell organelles; point to a common ancestry

Q17. Describe the structure and functions of various organelles in a mature animal cell(20mks)

Mitochondria

Has a double membrane the outer and the inner surrounding it; the inner folded to form cristae which increase surface area for attachment of respiratory enzymes

Golgi apparatus

These are stacks of membrane-bound sac-like structures that transport glycoproteins, they also pack glycoproteins

Lysosome

Are spherical shaped organelles bounded by a single membrane they contain lytic enzymes which destroy old worn-out organelles

Endoplasmic reticulum

Are membranes bond cavities in the cytoplasm

Smooth endoplasmic reticulum that transport lipids and steroids

Rough endoplasmic reticulum has ribosomes on its surface and transport proteins

Centrioles

Rod shape located outside the nuclear membrane; for the formation of cilia and flagella

Cytoplasm

It is a fluid medium where chemical reactions occur; contains organelles and inclusion

Granules; cell membranes

The cell membrane encloses all cell organelles; has a phospholipid layer between two protein layers, with pores that selectively allows substances to pass in and out/semi-permeable

Nucleus;

Has double membrane around it; with pores allow substances in and out

Ribosome

Are spherical in shape and suspended in the cytoplasm and attached to the endoplasmic reticulum; synthesis proteins

Q18. Describe how the male reproductive system in suited to its functions

Penis; high vascularized / spongy; sensitive glans penis become erect to allow entry/ penetration during copulation; scrotum; contains testis outside the body
Testis; contains numerous/ many seminiferous tubules ; on whose walls spermatogenesis take place; the process is favoured by lower temperature; contains Sertoli cells which nourish sperms until they are mature
Epididymis; which is the long and coiled tube for storage of sperms
Vas deferens; a muscular tube that upon contraction pushes sperms out and allow ejaculation; gametes are produced in large numbers to increase chances of fertilization; has a tail for swimming/ has a large number of mitochondria to provide energy for swimming (to reach the egg)

Q19. Describe the process of fertilization in flowering plants. (10mks)

Pollen grains land onto the stigma; and adhere to it as a result of cells secreting a sticky substance pollen absorbs nutrients; and germinates forming a pollen tube; the tube grows down to the ovary ; deriving nourishment from surrounding tissues; the pollen tube nucleus at the tip; the generative nucleus divides mitotically; to give rise to two nuclei; which represents the male gametes; the pollen tube penetrates the ovule/embryo sac, the tube nucleus breaks down; leaving two male nucleus; then enter into the embryo sac, where one fuses with egg nucleus; to form a diploid zygote; which develops into embryo the other male nucleus fuses with the polar nuclei; to from a tripod endosperm nucleus; which becomes the endosperm; this is called double fertilization

Q20. Describe the changes in the eye when moving from bright sunlight into a dimly lit room.(10mks)

In bright light the amount of light entering the eye should be reduced to ensure the eye is not damaged by the bright light; light enters the eye through the pupil; the radial muscles of the iris relax; while circular muscle contract; the diameter of the pupil decrease; less light gets into the eye; in dim light; the amount of light entering the eye should be more and hence the pupil should widen; radial muscles contracts; while circular muscles relax; causing the diameter of the pupil to increase and hence more light enters the eye

Q21. Describe how the cervical, lumbar and sacral vertebrae are suited to their function.(20mks)

Cervical vertebrae

Have vertebraterial canals for passage of artery; atlas has a (broad) surface for articulation with condyles of the skull to permit nodding; axis has odontoid process on the centrum to permit rotating movement/ turning act as a pivot for atlas /skill/movement of atlas; broad transverse processes for attachment of muscles; zygapophysis for articulation between vertebrae; has a short reduced spine for attachment of muscles; has wide neural canal; for passage of spinal cord; alternatively has wide neural canal for protection of spinal cord

Lumbar vertebrae

Broad/ long spine for attachment of muscle; long/large developed transverse processes; for attachment of muscles; has metapophysis and anapophysis; for muscles attachment; large/thick centrum for support

Sacral vertebrae

Anterior vertebrae have a well-developed transverse process; which is fused to the pelvic girdle; vertebrae fused, for strength; transmit the weight of the stationary animal to the rest of the body; sacrum has a broad base; short neural spine; for attachment of muscles

Q22. Explain the causes and the effects of soil erosion.(20mks)

(a) aerosols

These contain heavy metals like mercury; whose high concentration in plants leads to animals poisoning through the food chain causing death; the microbes in the soil are killed resulting in soil infertility

(b) acid rain

This increase the soil PH and causes damage/ death of pants/ animals; it also leads to leaching resulting in soil infertility

Are non-biodegradable; destroy the aesthetic values of the environment; they also become breeding sites are pests/ insects/ rodents which are a vector for disease; they also limit soil aeration/ decay/ microbial activities; the micro-organisms in the soil/ slowing down decomposition; this affects plants growth, and subsequently the life of animals

(d) Radioactive emissions; from nuclear power stations; and nuclear wastes affect the soil. They cause cancer/ mutations death of organisms.

Q23. State Characteristics of living things?

Nutrition

The process by which organisms obtain food and utilize nutrients
Organisms acquire nutrients (food) for various life process like growth

Gaseous exchange

The process by which living things take in oxygen and give out carbon (IV) oxide
Oxygen taken in is for respiration

Respiration

The process by which food materials are broken down chemically to produce energy
Energy is used in various activities like growth

Growth and development

Growth is the permanent increase in size
development is a change in the complexity of structure
Enables organism to acquire normal body size essentially for body function

Excretion

The process by which waste materials are eliminated
Enables organisms to eliminate waste materials that are toxic if accumulated

Movement/locomotion -

A change in whole organism or one part of the body
Enables organisms to acquire food, water and mates

Irritability

The ability of organisms to perceive the change in their surrounding
Enables organisms to respond to changes

Reproduction

The process by which organisms give rise to young ones
It prevents the extinction of organisms

Q24. KCSE 2020 Biology Paper 1 Qs 1-4

1.Name the taxonomic grouping that contains individuals with most similar similarities

Species

2.Name the characteristics of living organisms shown by each of the following:

a) Budding in Yeast

Reproduction

b) Enlargement of eye pupil in a dim light

Irritability/Response/Sensitivity

3.Explain why there is no grass in most dense forests

The dense forest prevent sunlight from reaching the grass thus the grass do not photosynthesize hence die due to lack of food

4.State one structural difference between a cell wall and a cell membrane

The cell wall is fully permeable while a cell membrane is semipermeable
The cell wall is made up of cellulose while a cell membrane is made up of a phospholipid layer

Q25. Biology Paper 1 KCSE 2020 QS 5 (Check the Diagram at the bottom)

5.The diagram below shows an organism in a certain kingdom

a. Name the Kingdom to which the organism belongs

Fungi

b. State the mode of nutrition for the organism

Saprophytism/Saprophytic nutrition

b. i. Name the part labelled E

Hypha/Hyphae; Accept Mycelium, Rhizoids

ii. State the two functions of the part labeled E

Secretes enzymes for external digestion
Anchors the organism
Absorbs digested food materials

Q26. KCSE 2020 Biology Paper 1 Q6 and Q7

6.State the importance of a well-developed blood capillary in the alveoli

Increases the surface for gaseous exchange

7. Name the genetic disorder in humans that is characterized by the inability of blood to clot

Haemophilia; Accept Hemophilia

Q27. EXCRETION AND HOMEOSTASIS

1. Explain the role of insulin in blood glucose regulation. (2 marks)

When the blood sugar level is above normal, it stimulates the liver cells; to convert excess glucose to glycogen/increase the rate of respiration/ convert glucose to fats. (Thus lowering the blood glucose level back to normal);

2. Name three methods by which plants eliminate their waste. (3 marks)

Diffusion;
Exudation;
Deposition;
Leaf fall;
Transpiration Mark first three only (3 marks)

3. In an investigation two people M and N drunk some amount of strong glucose solution. Their blood sugar levels were immediately determined and thereafter at one hour intervals for the next six hours. The results were shown in the table below.

a).In the grid provided, plot a graph for the blood glucose level against time for person M and N. (8 marks)

b). In man the normal blood sugar level is about 90ml/100ml of blood. Explain the change in the sugar level in person M during.

(i) The first 4 hours. (2marks)

Blood sugar level rises rapidly in the first hour; due to absorption of glucose from the ileum into the bloodstream;

ii) The 6th hour. (2marks)

Blood sugar level then starts declining as the person secrets insulin hormone (from the pancreas); which stimulates the liver cells to convert excess glucose into glycogen; (to lower blood glucose level)

c) i) Suggest a possible reason for the high blood sugar in person N. (1mark)

failure of the pancreas to secrete sufficient hormone insulin; which acts on the liver cells to lower the blood sugar level when it rises above normal;

ii) How can the high blood sugar in person N be controlled. (1 mark)

Regular intravenous injection of insulin; (so as to lower the blood sugar level);

d)The pancreas and the liver work together in the regulation of glucose in the blood.

The pancreas secretes glucagon hormone; which stimulates the liver cells to raise blood sugar levels by reducing oxidation of glucose/stimulates the conversion of stored glycogen to glucose.

4. State the role of these organs when the concentration of glucose in the blood is below normal. (2 marks)

i) What would be the effect of removing the pancreas from the body? (1 mark)

There would be no secretion of the hormone insulin; hence the blood sugar level would rise far above normal resulting in diabetes mellitus;

ii) Distinguish between diabetes mellitus and diabetes insipidus. (2marks)

Diabetes mellitus – is a kidney disorder due to insufficient or no secretion of insulin by the pancreas, leading to high blood sugar level. (Hence presence of glucose in urine);
Diabetes insipidus – kidney disorder due to failure of the pituitary gland to secrete enough antidiuretic hormone; hence little or no water re – absorption in the kidney tubules;

iii). Name two substances that are excreted through diffusion process in plants. (2mks)

. Carbon (IV) oxide;
Oxygen;
Water vapour; Any 2 x 1

5. (a) Arrange the following nitrogenous waste products in order of decreasing toxicity: urea, uric acid and ammonia.(1mk)

Ammonia, urea, uric acid;

(b) Explain why desert animals excrete their nitrogenous wastes in form of uric acid. (1mk)

It requires little amount of water to eliminate/excrete;

6. Name one waste product that is transported in the blood but not removed by the kidneys. (1mk)

Carbon (IV) oxide;

7.The table below compares the approximate concentration of certain substances in plasma glomeruli filtrate and urine.

a) Account for the absence of

(i) Glucose in the urine. (1mk)

It is completely reabsorbed selectively in the proximal convoluted tubule

(ii) Protein in glomerular filtrate. (1mk)

Proteins have big molecules that cannot be ultra-filtered in the glomerulus.

b) (i) Why is the percentage of urea highest in urine? Give two reasons. (2mks)

All the urea is excreted since it has no use in the body i.e. it is toxic.
A lot of water is reabsorbed in the distal convoluted tubule leaving much urea. Urea is actively secreted into the tubules;

c) How would the composition of urine differ from the one given above in case of:

(i) High protein diet. (2mks)

Urea concentration will increase due to an increase in the deamination process; to eliminate excess amino acids.

(ii) Streneous exercise. (2mks)

The concentration of urea will go down; because some urea will be excreted through sweating;

8. Describe the regulation of blood sugar level in man. (10mks)

When the blood sugar rises, it is detected by the hypothalamus; which stimulates the pancreas; to release insulin; through the blood, the insulin gets to the liver; where it stimulates the conversion of excess glucose to glycogen and fats which are stored; the insulin also enhances rapid breakdown of glucose in the muscle cell; these events lead to a fall in blood sugar back to normal; When the blood sugar is low, the hypothalamus; stimulate the pancreas to release glucagon; which via the bloodstream; get to the liver, where it stimulates the liver to convert glycogen to glucose; and fats to glucose; there is also less breakdown of glucose in the cells; leading to a rise in the blood sugar level back to the norm; total 14mks, maximum 10mks.

9. (a) Given a sample of urine, name one test you would carry out to determine if it was obtained from a person suffering from diabetes mellitus. (1 mark)

Reducing sugar test. (1mk);

(b) What results are expected if one is diabetic? (2 marks)

When the mixture of urine and Benedict solution is heated the colour of the mixture turns from blue to green - to yellow – to orange/brown/red. (1mk); indicating the presence of reducing sugar (1mk);

10. (a) State three processes by which flowering plants excrete waste products and for each process name two waste products that are eliminated. (6 marks)

(a) Process Products

Exudation/guttation; Resins, gums, latex, rubber, calcium oxalate, salts, water.(any two) (2mks)
Transpiration/Diffusion; Water, carbon (IV) oxide, oxygen. (any two) (2mks)
Deposition/leaf fall; Tannins, caffeine, morphine, nicotine, cocaine (any two) (2mks)

11. a) What is diabetes mellitus? (1mk)

A condition in which blood sugar level is high and uncontrolled. Caused by lack of insulin in the blood due to the malfunctions of the pancreas;

b) How can it be controlled? (1mk)

Administration of insulin injections/ tablets
Avoid foods rich in sugar

12. Explain what happens to excess amino acid in the liver of humans (3marks)

Amino acids are broken down into amino groups and carboxyl group deamination;
The amino group combines with hydrogen forming highly toxic ammonia which combines carbon (IV) oxide to form urea; (3mks)

13. Explain why plants do not require specialized excretion organs (2marks)

Plants reuse some of their waste product; Animals do not
Produce lower metabolic waste than animals;

14. Explain the role of human skin in;-

(i) Thermoregulation (14marks)

when the temperature is low (cold), the erector Pilli muscles contract; making hair follicles to stand erect; the hair follicles trap a layer of hair; between them which reduces heat loss due to poor heat conduction through them; when the temperature is high the erector Pilli muscle relax; thus making the hair lie flat; thus reducing the air trapped and more heat will be lost to the environment
The skin has sweat glands that secrete sweat; when temperatures are high water from the sweat evaporates taking away latent heat of vapourization; when the temperature is low, no sweat is produced.
When the temperature is high, the blood vessels vasodilate; and this encourages loss of heat; as more blood flow close to the skin surface; when temperatures are low, blood vessels vasoconstrict; less blood flows close to the skin surface; hence less heat is lost to the environment.
The skin has adipose tissue for insulation against heat loss.

(ii) Protection (6marks)

Skin has a cornified layer made of dead cells; which protects the entry of bacteria and inner tissues from mechanical damage; the sebaceous gland, secret sebum; which has antiseptic properties; hence protects the body from bacteria. The skin has melanin pigment which protect the body from harmful U.V rays.

15. The diagram below illustrates part of a nephron from a mammalian kidney.

(a) Name the fluid found in the part labelled Q. (1mk)

Glomerular filtrate;

(b) Identify the process responsible for the formation of the fluid named in (a) above. (1mk)

Ultra-filtration / pressure filtration;

Antidiuretic hormone / vasopressin; Aldosterone;

16. a) Identify the source of urea that is removed via the kidneys in a healthy human being. (1mk)

Deamination of excess proteins / amino acids in the liver;

b) Explain why a pregnant woman excretes less urea compared to a woman who is non- pregnant. (2mk)

Amino acids are used in the formation of foetal tissues; thus has less excess to be eliminated;

17 a) Explain what happens in humans when the concentration of glucose in the blood rises above the normal level. (3)

Insulin is produced which increases oxidation of glucose; facilitate conversion of glucose into glycogen / fats for storage; inhibits conversion of glycogen into glucose;

b) Describe the process of urea formation. (7 marks)

18. Name two processes by which flowering plants excrete waste products. (2mks)

Exuddation / Guttation;
Transpiration / diffusion;
Deposition / leaf fall / abscission. (any two) (2mks)

19. Describe how excretion takes place in the

i) Mammalian kidney (10 marks)

Blood reaches the kidney from the renal artery, which branches into the renal arterioles. Arterioles further branches into afferent arterioles, which drain into the glomerulus. Enclosed in the Bowman‟s capsule.
The afferent arteriole are wider than the efferent arterioles causing higher pressure to develop in the glomerulus, this causes ultrafiltration of the plasma into the Bowmans capsule, the liquid part of the blood is filtered out, forming glomerular filtrate. This filtrate contains both waste and useful products.
The filtrate moves to the proximal convolute tubules, where selective re-absorption of glucose, amino acids, and some water and vitamins takes place, re-absorption occurs by diffusion and active transport.

The filtrate passes in to the loop of henle where the concentration of sodium and chloride ions are raised to favour the reabsorption of water by osmosis. The filtrate that remains mainly consist of excretory products namely : urea, uric acid, excess water and mineral salts, these are passed to the distal convoluted tubules, where the remaining useful substances mainly water and mineral salts are re-absorbed.
The urea, uric acid, ammonia ions, excess water and excess mineral salts form urine which is removed through the ureter to the urinary bladder and later excreted out of the body.

ii) Green plants (10 marks)

Diffusion :

waste product may be eliminated when concentration gradient exists, such products include carbon (iv) oxide through the lenticels and stomata. iii) Exudation refers to the process by which plants release wastes as components of their secretion such as latex, gums, salts resins, calcium pectate

Transpiration:

this is the process by which plants lose excess water in the form of water vapor through the stomata, lenticels and cuticle into the atmosphere

Guttation

Leaves of certain plants such as potatoes and tomatoes have specialized gland called hydathodes at tips and margins which secrete droplets of water, this aids in elimination of excess water and some dissolved salts.

Deposition

Plants store little waste products in their harmless and insoluble form in tissues and organs such as leaves, fruits and flowers. The wastes are eliminates when these parts die or are shed off from the plant. Such waste include alkaloids,(nicotine, caffeine, oxalates) glycosides (sugar compounds such as plants oils and tannins.

20. (a) Explain why glucose does not appear in the urine of a healthy person even though it is filtered in the Bowman‟s capsule of a mammal. (2mks)

All is actively reabsorbed at the proximal convoluted tubule;

(b) In a certain person, glucose appeared in the urine. State the disease the person was suffering from. (1mk)

Diabetes mellitus;

Q28. Excretion and Homeostasis Answers

Q29. KCSE Biology The Cell

1. Name the function of the following organelles found in a cell. (2 mark)

a) Centrioles

b) Nucleolus

2. The following diagram shows a specialized cell.

(a) identify the specialized cell. (1 mark)

(b) State the function of the cell named in (a) above. (1 mark)

3. The diagram below shows a certain cell. Use it to answer questions that follow.

(a )Identify structures labelled A, B, C, and D. (4 marks)

(b )Measure the length of the distance between X and Y. If the magnification of the cell is X 10,000.

(d) With reason identify the kingdom from which the cell was obtained. (2marks)

4. What is the importance of fixation in the preparation of temporary slides? (1mk)

5. Why are the following steps taken when preparing a crosssection of a leaf for viewing under the microscope?

(a) Cutting thin section. (2 marks)

(b) Placing the section in water. (2 marks)

6. State the functions of the following; i) Lysosomes ii) Ribosomes iii) Mitochondrion (3marks)

7. A student was using a microscope whose eyepiece lens was marked X4. The high powered objective lenses were marked X10. Calculate the total magnification of the microscope (2marks)

8. The diagram below represents microvilli on epithelial cells

Name the parts A and C (2marks)

Name two parts in the human body where the above epithelial cells are found. (2marks)

(a) Name the parts A and C

(b) Name two parts in the human body where the above epithelial cells are found. (2marks)

9. Distinguish between resolving power and magnifying power of a microscope (2 Marks)

10. Name the cell organelles responsible for:

(a) Protein synthesis. (1mk)

(b) Destroying worn-out organelles. (1mk)

11. (a) Lokori school Biology students used a microscope with x40 objective lens and x5 eyepiece lens which had a 2mm radius. Calculate the area of the field of view in micrometres. (2mks)

(b) What is the average size of the cell in micrometres? (2mks)

12. State three differences between plant cell and animal cell (3marks)

13. State one function of revolving nose piece in the light microscope (1mk)

Q30. Genetics Q and A

1a) what is a test cross? (1 mark)

b) The figure below is a structural diagram of a portion from a nucleic acid strand.

Giving a reason, name the nucleic acid to which the portion belongs. (2 marks)

c) Write down the sequence of bases of the complementary strand to that shown above. (1 mark)

2. The diagram below shows a template strand of the Deoxyribonucleic acid molecule.

i) Complete the diagram by drawing the missing complimentary strand. (1 mark)

ii) Name two chemical components that make the backbone of deoxyribonucleic acid molecule. (2marks)

(a)A woman who is a carrier for haemophilia got married to normal man. Work out the genotypes of the offsprings. Take the gene for haemophilia to be “h” (4 marks)

(b)Name one disorder in humans due to chromosomal mutations. (1marks)

3. Explain why the garden pea plant was preferred by Gregor Mendel in his crossing experiments (3mks)

4. Give two structural differences between DNA and RNA molecules. (2mks)

5. In a certain plant species which is normally green, a recessive gene for colour (n) causes the plant to be white when present in homozygous state such plants die at an early stage; The plants are pale green in colour when in heterozygous state and grow to maturity.

(a)Give a reason for the early death of plants with homozygous recessive gene. (1mk)

(b)If a normal green plant was crossed with the pale green plant, what would be the genotypes of the F1 generation (use punnet square to work out the answer)

(c)If seeds from the heterozygous plants were planted and the resulting seeds planted, work out the phenotypic ratio of plants that would grow to maturity. (3mks)

(d)Explain the occurrence of the pale green colour in the heterozygous plants. (1mk)

6. Mr. Juma has sued Serenity Hospital on grounds that their child was wrongly identified such that they got the wrong one. The child is blood group O. Mr. Juma is blood group AB while Mrs. Juma is heterozygous blood group A.

(a) Work out the possible blood group of their offsprings. (4 marks)

(b) Is Mr. Juma justified in his claims? (1 mark)

7. The diagrams below illustrate some chromosome mutations.

(a)Identify the mutations illustrated above. (3 marks)

(b) Give an example of a disorder in humans caused by mutation A above. (1 mark)

(d)Name two mutagens. (2 marks)

(e)Give an example of a beneficial mutation in plants. (1 mark)

8. a) Name two disorders in human caused by gene mutation (2marks)

b) Give two examples of continuous variation in plants (2marks)

9. In maize the gene for the purple colour is dominant for the gene for white colour. A purple colour was crossed with heterozygous plant. Using letter G to represent the gene for purple colour, work out the genotypic ratio of the offspring. Show your working. (5marks)

10. The following are short messages (sms) on cell phone communication between Mrs. Mkenzie and her husband. They can be used as analogies of gene mutation

(a)For each of these messages identify the type of gene mutation illustrated (4marks)

(b)State one example of chromosomal mutation that lead to

(i)Change in chromosomal structure (1mark)

(ii)Change in chromosomal number (1mark)

(c)Explain why genetic counselling is termed as one practical application of genetics (2marks)

13. a) what is sex linkage? (1mark)

b) Name the sex linked trait that are only in male (2marks)

14. Pure breed of red cows and pure breed of white bulls were crossed to give F1 calves which had a mixture of red and white coat known as roan. The F1 were selfed.

(a)Using letter R to represent gene for red colour and W to represent gene for white colour work out the phenotypic ratio of F2. (4 marks)

(b)Work out the genotypic ratio of a cross between F1 offspring and white bull. (3marks)

(c)Comment on the gene(s) controlling the colour of coats in cattle mentioned above. (1mark)

15. (a) What is mutation? (1mark)

(b) Name one disorder caused by gene mutation and one disorder caused by chromosome mutation. (2marks)

Gene mutation

Chromosome mutation

16. a) What is heterozygous advantage? (1 Mark)

b) Give an example. (1 Mark)

17. (a) What is meant by the term (2mks)

(i) Allele

(ii)Test cross

(b) Describe the following chromosomal mutations:

i) Inversion (1mks)

ii) Translocation (1mks)

(c) In mice the allele for black fur is dominant to the allele for brown fur. What percentage of offspring would have brown fur from a cross between heterozygous black mice? Show your working. Use letter B to represent the allele for black fur. (4mks)

18. Explain the meaning of the following terms

(i)Phenotype (1 mark)

(ii)Test cross (1 mark)

19. The diagram below represents a stage during cell division

ii) Give two reasons for your answer in a) i) above (2mks)

b) Name the structure labeled M (1 mark)

20. A cross between a red flowered plant and while flowered plant produces plants with pink flowers. Using letter R to represent the gene for red colour and W for white colour,

(a)What were the parental genotypes? (1 mark)

(b)Work out a cross between F1 plants. (4 marks)

ii) Genotypic ratio of F2 plants (1 mark)

(d)Name the characteristic in humans which is controlled by multiple alleles (1 mark)

Q31. KCSE Biology Form 4 - Support and Movement

1.The diagram below represents a mammalian bone.

(a)State the function of the part labeled K and L (2mark)

(b)State the region of the body in which the above bone is found. (1 mark)

2. (a) Name the hard body covering found in organisms of the phylum arthropoda. (1mk)

(b) Give two uses of the structure mentioned in (a) above. (2mks)

3.Below is a diagram showing the forearm bones and muscles covering them?

(a) Name the bones represented by T, X, Y and Z.

(b) Name the joint formed between:

(i) T and X.

(ii) Y and X.

(d) What happens to each muscle as the arm is straightened.

(e) Name two strengthening tissues in woody stems.

4. The diagram below represents a bone of a mammal.

(a)Identify the bone. (1 mark)

(b)Name the part marked X. (1 mark)

(c)Name the bone that articulates at the part labelled F. (1 mark)

(d)Explain one way in which the bone is adapted to its function. (1 mark)

5. The diagram below shows a joint in a mammal. Study it and answer the questions.

(a)State the functions of parts A and B (2marks)

(b)Name the type of joint illustrated by the diagram (1mark)

(c)State two adaptations of joint named in (b) Above (2marks)

6. Name two structures in herbaceous stems that enhance their support. (2mk)

7. The diagram below represents a bone obtained from the hind limb of a goat.

(a)Identify the bone. (1mk)

(b)Name the type of joint formed at the part labelled T. (1mk)

8Explain how the following tissues are adapted to provide mechanical support in plants.

(a)Collenchyma

(b) Sclerenchyma

9. State the role of intervertebral discs (1 mark)

10. State three structural differences between biceps muscles and muscles of the gut (3marks)

11. What are the functions of the odontoid process found on the axis bone of the cervical vertebra?(2mks)

12. Explain the adaptations of thoracic, cervical and lumbar vertebrae to their functions (12 marks)

13. a. Name two bones that form the pectoral girdle. 2mks

(b) Name the cavity formed by the scapula that form a joint with the humerous. 1mk

14. The diagram below represent a mammalian bone.

(a)Name the bone.

(b)(i) Which bone articulate with the bone shown in the diagram at the notch ? (1 mark)

ii) Name the type of joint formed when the bone in b(i) articulate. (1mark)

15. a) Name two supporting tissues in plants. (2 marks)

(b)Study the diagram below and answer the question that follows.

i) Identify the muscle represented by X and Y. (2 marks)

ii) Describe how muscle X and Y cause straightening of joint Z. (2 marks)

(c)Name joint Z. (1 mark)

16. The figures below illustrate specialized cells in an animal body.

(a)Identify the cell M and N. (2marks)

(b)State the structural differences between M and N (2marks)

©Which of the above specialized cells is found in the gut. (1mark)

17. The diagram below shows the bones and two of the muscles in the human arm

(a)Name the parts A, C, E and F. (4marks)

(b)i) Name the type of joint present in part X and Y (2marks)

ii) What type of movement is possible at point X. (1marks)

c) What happens when the muscle labelled C contracts. (1mark)

18. State the importance of support in plants. (3marks)

19. The diagram below represents a human arm. Study it and answer the questions that follow.

(a)Name bone T and R (2marks)

(b)Name muscle C and D (2marks)

(c)i) Identify the fluid found at joint 2. (1mark)

ii) State the function of the fluid in (i) above. (1mark)

(d)i) What is the type of the joint found at part labeled 1. (1mark)

ii) Differentiate between a tendon and a ligament. (1mark)

20. a) Distinguish between a hinge joint and a ball and socket joint. 1mk

b) i) Name the cartilage found between the based of the vertebral column. 1mk

ii) State the function of the cartilage named in b (i) above 1mk

Q32. KCSE Form 3 Biology - Ecology

1. a) What is synecology? (1 mark)

b) Name two abiotic factors in water that affect living organisms. (2 marks)

2.Complete the table below: (3 marks)

3.The diagram below represents the recycling of nutrients in a certain ecosystem. Study it and answer the questions that follow.

(a)Name the tropic level represented by M. (1mark)

(b)Name the process represented by I, II, and III. (3 marks)

(c)Name the organism involved in process II. (1mark)

(d)What would happen within the ecosystem if all secondary consumers were eliminated? (3 mks)

4.What is nitrogen fixation? (1mk)

5. Describe the nitrogen cycle. (20mks)

6. The table below shows the approximate numbers of organisms found in an ecosystem.

a) Using the information in the table draw a pyramid of numbers. (3 marks)

b) Explain what would happen to the other organisms if all the lizards suddenly died of ( 2 mks)

7. (a) Name the bacteria found in the root nodules of leguminous plants. (1 mark)

(b) What is the role of the bacteria named in (a) above? (1 mark)

8. The diagram below represents the nitrogen cycle.

(a)Identify the processes labelled A and D. (2 marks)

(b)Name the compound represented by B. (1 mark)

(c)Name the group of organisms labelled C. (1 mark)

(d)(i) Name the group of plants that promote process A. (1 mark)

(ii) In which part of the plant does process A take place? (1 mark)

(iii)How would excess pesticides in the soil interfere with process A? (2 marks)

9. The number and distribution of stomata on three different leaves are shown in the table below;

Suggest the possible habitat of each of the plants from which the leaves were obtained (3marks)

(b)State the modification that may be found in the stomata of leaf C (2marks)

10. Explain why the biomass of producer is greater than that of the primary consumer in a balanced ecosystem (1mark)

11. Explain the Ecological importance of fungi to plants (2marks)

12. Distinguish between community and population (2marks)

13. Name the disease caused by the following causative agent in humans (2marks)

(i)Salmonella typhi

(ii)Plasmodium falciparium

14. In an ecological study, a grasshopper population and that of crows was estimated in a certain grassland area over a period of one year. The results are as shown in the table below;

a. (i) What is the relationship between the rainfall and grasshopper population? (1mark)

ii) Account for the relationship stated in a (i) above. (3marks)

b. Explain the relationship between the grasshopper population and that of the crows. (3marks)

c. If the data was used in the construction of a pyramid of numbers, what would be the trophic level of:-

i) Grasshopper

ii) Crows

iii) The grass in the study area. (3marks)

d) If the area studied were one square kilometre, state-

(i)One method that could have been used to estimate the crow population (1mark)

(ii)One method that could have been used to estimate the grasshopper population.(1 mark)

e) Suggest what would happen if a predator for grasshoppers entered the study area (2 marks)

f) What is meant by the term carrying capacity? (1mark)

g) Why would the carrying capacity of wild animals in woodland grassland be higher than that of cattle? (2marks)

15. What is an ecosystem? (1mark)

Habitat (1mark)

Ecological niche (1mark)

16. State three measures that can be taken to control infection of man by protozoan parasites.( 3mark)

17. Explain the likely effect on humans and other organisms of untreated sewage discharged into a water body that supplies water for domestic use. (3mk)

18. a) State the major factor in the „Global warming‟ experienced in the world today. (1mk)

b) Suggest two ways of reducing Global warming. (2mk)

19. A group of Form four students set up an experiment to investigate a biological process using termites. They used a small box in which a portion was covered with black paper and had moist soil. The open part had dry soil. Termites were placed inside an open area of the box.

(a)Predict what happened to the termites after 30 minutes. (1mk)

(b)What form of response is exhibited by termites? (1mk)

(c)State one biological significance of the above response to termites. (1mk)

20. During an ecological study of a lake, a group of students recorded the following observations.

Planktonic crustaceans feed on planktonic algae;
Small fish feed on planktonic crustaceans, worms and insect larvae;
Worms feed on insect larvae;
A bird species feeds on small fish, planktonic crustaceans, worms and large fish;
Insect larvae feed on planktonic algae;
Large fish feed on small fish.

(a)From this record of observations, construct a food web. (4 marks)

(b)From the food web, isolate and write down a food chain that ends with:-

(i)Bird species as a secondary consumer. (1 mark)

(ii) Large fish as a tertiary consumer. (1 mark)

(c)The biomass of the producers in the lake was found to be greater than that of primary consumers. Explain this observation. (2 marks)

(d)Using the food web, identify three pairs of organisms that compete for food in the lake and for each case, name the food being competed for. (6 marks)

(e)(i) State three ways by which human beings may interfere with this lake ecosystem. (3 marks)

(i) Explain how each of the ways stated in (e) (i) above may affect life in the lake. (3 marks)

21. A person walked bare feet in a swampy area. After a few weeks, he started experiencing abdominal pains and diarrhoea. His urine and stool contained blood.

(a)Name the disease the person was likely to be suffering from and the causative agent of the disease

(i)Disease (1mark)

(ii)Causative agent (1mark)

(b)Apart from avoiding walking bare feet in a swampy area. State two other ways of controlling the disease. (2mks)

22. State three adaptive features of a desert plant. (3 marks)

23. Equal grams of maize flour were placed into two boxes K and L respectively. Equal numbers of weevils were then introduced into the boxes. The boxes were kept under similar environmental conditions. The weevils were counted at intervals and the results were recorded in the table below.

a) Using a suitable scale and on the same axes draw two graphs of the approximate number of weevils present against number of days after the introduction of weevils on the graph paper provided. (8marks)

(b) What were the approximate number of weevils present in the two boxes on the 70th day? (2marks) Number in K:

Number in L:

(ii) Between which days were the population difference greatest? (1mark)

(d)Account for the shape of graph L between day 5 and day 100. (4 marks)

(e)State factors that would make the human species assume the curve K above. (4marks)

24. What is the meaning of the following terms? (2mks)

(a)Autecology:

(b)Synecology:

25. (a)Name the causative agent for the following diseases:-

(i) Amoebic dysentery (1mk)

(ii)Schistosomiasis

(b) Explain why primary productivity in the aquatic environments reduce with an increase in depth. (2mks)

26. Use the graph below to answer the questions that follow.

(a)Calculate the difference in nitrate concentration between the highest and lowest. (1mk)

(b)How can an increase in nitrate concentration in the river lead to the death of fish? (2mks)

(c)Suggest one possible source of nitrate that lead to pollution in a river. (1mk)

27. (a) A wild beast in Maasai Mara National Park was found to be infested with a lot of ticks. State the trophic level occupied by the following organisms. (2mks)

(i). Wild beast:

(ii). Ticks

(b) Study the food below representing a certain ecosystem and use it to answer the questions that follow.

(i)Write down a food chain in which the vulture is a tertiary consumer. (1mk)

(ii)What would be the effect of introducing gazelles and termites into the ecosystem? (1mk)

(c) During an ecology, students collected and marked 40 ants and then released them. After 2 days, the students captured another 100 ants, 40 of which had been marked previously.

(i)How many ants were there in the compound? Show your working. (2mks)

(ii)Give two assumptions of this method in sampling animal population. (2mks)

Q33. KCSE Biology Form One - Introduction to Biology

KCSE FORM I - BIOLOGY

1. Study the diagram below and answer the questions that follow:

(a)Identify the above apparatus. (1mk)

(b)State the function of the above apparatus. (2mks)

(c)Name an apparatus that can be used for catching insects on barks of trees or rock surfaces. (1mk)

(d)Name the branch of Biology that deals with the study of birds. (1mk)

2. Some form one students wanted to collect the following animals for study in the laboratory. State the suitable apparatus they should use.

(i)Flying insects. (1mk)

(ii)Crawling stinging insects. (1mk)

(iii)Small animals from tree barks. (1mk)

3.A scientific space craft brought some material to earth from the outer space. Explain how one would establish if the material is living or non-living. 2mks

4.State the field of biology described below:

(a)Study of interrelationship of living things in their surroundings. (1mark)

(b)Study of fossils. (1mark)

5. Study the diagram below and answer the questions that follow.

(a)Identify the apparatus. (1mark)

(b)State the functions of the part labeled x. (1mark)

6. Name the branch of Biology that involves the study of: 2mks

(a)for the sake of classifying them

(b)Microscopic organisms

7. Differentiate between movement and locomotion as used in characterizing living things. (1mk)

8. State one function of each of the following apparatus in the study of living organisms.

(a)Sweep net (1 mark)

(b)Pooter (1 mark)

(c)Magnifying lens (1 mark)

9. State the functions of the following apparatus;

Pitfall trap (1mk)

10. Plants do not have ability to move from one place to another. How do they compensate for this in order to carry out the following processes.

(a)Reproduction (2 marks)

(b)Nutrition (2 marks)

11a) Name the most suitable biological equipment for collecting the following organisms;

(i)moths from a coffee farm ............................................................................... (1 mark)

(ii)ants from a tree trunk ...................................................................................... (1 mark)

b) State the term that refers to the scientific system of assigning two names to an organism.(1mk)

12.Name two major branches of biology. (2 marks)

13.What name is given to a scientist who studies the following:

(a)Insects (1mark)

(b)Plants (1mark)

(c)Identification and classification of living organisms. (1mark)

14Give the name of the study of (4 marks)

(a)The cell

(b)Microorganism

(c)Insects

(d)Fungi

Q34. CELL PHYSIOLOGY

1. State three roles of osmosis in plants (3marks)

2. Potato cylinders were weighed and kept in distilled water overnight. They were then reweighed.

(a)Calculate the average mass of the potato cylinders at the end of the experiments. (Show your working). (2mks)

(b)Explain why the mass of the cylinders had increased. (3mks)

3. The following set up was used to investigate a physiological process in life.

(a) (i) Name the physiological process that was being investigated. (1mk)

(ii) What is the representative of the visking tubing in life? (1mk)

(b) (i) State the observation that would be made in the visking tubing after few minutes. (1mk)

(ii) Explain why similar results were not obtained inside the beaker. (2mks)

4. Two potato cylinders were carefully dried on a blotting paper and weighed. Each piece weighed 2 grams. One was placed in each test tube as shown in the diagram below.

(a)After 48hrs, which potato cylinder will be heavier. Explain. (2 marks)

(b)Name the substance whose movement was responsible for the weight changes in the potato cylinder you identified in (a) above. (1 mark)

(c)Name the process which was responsible for the movement of the substance you identified in (b) above. (1 mark)

6. An experiment was set up as shown below

What are the observations made after 30 minutes in the experiment above (2marks)

7. State three differences between osmosis and active transport. (3mk

8. What is meant by the following biological terms?

i) Crenation (1mk) ii) Haemolysis (1mk) iii) Plasmolysis (1mk)

9. Examine the diagram below carefully and use it to answer the questions that follow.

(a)Name the parts X, Y and Z. (3 marks)

(b)State the main substance that make-up the part labelled W. (1 mark)

(c)Name the process through which mineral salts move into the structure labeled X. (1 mark)

(d)Explain what happens to a red blood cell when placed in distilled water. (3 marks)

10. Define the following terms in relation to a cell. (3mks)

(i)Isotonic solution:

(ii)Hypotonic solution:

(iii)Hypertonic solution:

11. (a) Define active transport. (2mks)

(b) State two roles of active transport in animals. (2mks)

13. In an experiment, a visking tubing was half filled with concentrated sugar solution containing methylene blue dye. Both ends were tied well to prevent leakage. It was then rinsed with distilled water and immersed in a beaker containing distilled water. The set-up is shown below. After 6 hours the water in the beaker turned blue, and the visking tubing was swollen with more solution.

(a)Explain why the visking tubing was swollen with the solution at the end of the experiment (3 marks)

(b)Name the process through which the water in the beaker turned blue. (1 mark)

(c)Distinguish between diffusion and active transport in a human body (2 marks)

(d)State two roles of active transport in the human body. (2 marks)

12. A group of students set up an experiment as shown below. The experimental set up were left for 20 minutes.

The observation after 20 minutes were as shown in the table below.

(a)State the process being demonstrated in this experiment. 1mks

(b)Explain the results in set up A. 3mks

14. An investigation was set up as shown below.

After 30 minutes, starch suspension had turned blue-black while iodine solution retained its colour.

(a)Name the physiological process that was being investigated in the experiment. (1mark)

(b)Account for the results observed after 30 minutes. (3marks)

14. A group of form 1 West students set up an experiment to demonstrate a certain physiological process. The set up was left to stand for 20minutes.

(a)Name the physiological process demonstrated in the experiment (1mark)

(b)What observations were made after 20minutes? (2marks)

(c)Explain the observations you have made in (b) above. (3marks)

(d)State two roles of the process you have made in (b) above. (3marks)

15. four cylinders of potato were carefully dried on blotting paper and weighed. Each piece weighed 3g. One was placed in each as shown in the drawing below.

(a)After 48hours, which potato would be the heaviest 2mks

(b)Name the substance whose movement was responsible for the weight changes in potato cylinders. 1mk

(c)Name the process which was responsible for this movement in tubes B, C and D. 1mk

16. Explain the term Osmotic potential in plant physiology. 1mk

17. Differentiate between osmosis and diffusion. (4 marks)

18. List three factors that affect the process of active transport. (3 marks)

19. In an experiment two equal volumes of solution L and M were placed into visking tubing. The visking tubing was suspended into beakers containing equal volumes of solutions K. The set –up is as shown in the diagram A and B. The set-up was allowed to stand for 45minutes and results are as shown in the diagrams

(a)Name the process that was being demonstrated. (1mark)

(b)Explain the results that were obtained at the end of the experiment in

(i)Set-up A. (2marks)

(ii)Set up B. (2marks)

(c)What is the biological importance of the process demonstrated in this experiment to plants? (2marks)

20 How do the followin factors affect the rate of diffusion?

(a)Diffusion gradient (1 mark)

(b)Surface area to volume ratio (1 mark)

Q35. KCSE BIOLOGY F4 - EVOLUTION

(1)The wings of a bird and those of a housefly adapt the two organisms to a boreal habitat.

(i)Give the evolutionary process that may have given rise to these structures. (1 mark)

(ii) What name is given to such structures? (1 mark)

(2)The wings of a bird and that of insects are analogous structures.

(a)What are analogous structures? (2mks)

(b)Name this type of evolution. (1mk)

3. Name a vestigial structure found in:

(a)Man. (1mk)

(b)Whale. (1mk)

4. In a prolonged drought period, forage was scarce. It made animals reach out for higher forage and this way the giraffes got the stretched long necks.

(a)What is the term used for a characteristic such as the long necks outlined? (1 mark)

(b)What is the name given to the theory that describes the evolution of such structures like the long necks? (1 mark)

(c)State and explain the limitation of the theory you named in (b) above. (2 marks)

5. The paddles of whales and the fins of fish adapt these organisms to aquatic habitats.

a) Name the evolutionary process that may have given rise to these structures. (1mk)

b) What is the name given to such structures? (1mk)

c) Give two examples of vestigial organs in man. (2mk)

6. a) Outline the main features of the Lamarckian theory of evolution. (2mk)

b) In view of modern genetics, explain why Lamarck’s theory is unacceptable. (1mk)

c) Name one factor in nature that increases the process of evolution. (1mk)

7(a) Define the term evolution (1 mark)

(b) State four sources of evidence that support the theory of organic evolution. (4 marks)

8. After a colony of penicillin-sensitive bacteria was exposed to antibiotic penicillin, penicillin-resistant bacteria emerged. Explain this observation (2 Marks)

9. What is meant by speciation? (2 Marks)

10. a) what is natural selection? (4marks)

b) Describe four evidences of organic evolution. (16marks)

11. (a) Distinguish between homologous and analogous structures in evolution. (2mks)

(b) Give one limitation of fossil records as evidence for organic revolution. (1mk)

12. a) What are vestigial structures? (1 mark)

b) State one major importance of convergent evolution to living organisms. (1 mark)

c) Why is Larmarck‟s theory not popular with scientists? (1 mark)

13. (a) What is meant by the following term Adaptive radiation (1mk)

(b) Evolution is an ongoing process and is still going on even today. State two pieces of evidence that suggest that evolution is still taking place. (2mks)

(i)Predators

(ii)Diseases

(a) Define:

(i)Chemical evolution. 2mks

(ii)Organic evolution. 2mks

14.50 black mice and 50 white mice were released into an area inhabited by a pair of owls. After four months 38 of the black mice and 9 of the white mice were recaptured.

(a)How this observation would be explained. (2 marks)

(b)Name the theory of evolution that support the results in (a) above. (1mark)

(c)Name two vestigial structures in man. (2 marks)

16. State two advantages of natural selection. (2 marks)

17. a) What are fossils? (1mark)

(b) State two different types of fossils. (2marks)

c) State two limitations of the use of fossils as evidence of evolution.(2marks)

18. a) Give two reasons why the evolution of humans enabled him to survive better than his hominid ancestors. (2marks)

b) Why is Lamarck‟s theory of evolution not accepted by biologists today?

9. a) What is meant by the term vestigial structures? 1mk

b) Name the type of evolution illustrated by

(i)Hind limbs of birds 2mks

(ii) Wings of birds and insects. (1mark)

20. a) What is the difference between Darwinian and Lamarckian theories of evolution. 2mks

Q36. KCSE F2 BIOLOGY - GASEOUS EXCHANGE

1. State four adaptations of respiratory surfaces. (4 marks)

2. Study the diagram and use it to answer the questions that follow.

3. Mention the equivalent of the following in the mammalian breathing system.

(a)Bell far……………………………………………………………… (1mk)

(b)Balloon……………………………………………………………… (1mk)

(c)Rubber sheet………………………………………………………… (1mk)

4.Name the structure for gaseous exchange in

Tadpole …………………………..…………………………………. (1mk)

Grasshopper………………………………………………………….. (1mk)

5. Describe the photosynthetic theory of the opening and closing of the stomata. (10mks)

6. (a) Which substance in the cigarettes smoke may cause lung cancer. (1 mark)

(b) The table below shows differences in the air breathed in and out.

(7). What is the reason for their differences? (2 marks)

(8). The diagram below represents an organ of gaseous exchange.

(a)What is the name of the organ? (1 mark)

(b)Name the class to which the animals that have the organ you identified in (a) above belongs. (1 mark)

(c)State one way in which structure X is adapted for gaseous exchange. (2 marks)

7. How does carboxyhaemoglobin lead to death? (2 marks)

8. Explain the following

(a) (i) When transplanting a seedling, it is advisable to remove some of the leaves. (ii) There are generally fewer stomata on the upper side of a leaf than on the lower side 1 mark)

(b) Design a simple experiment to illustrate this observation in (a) (ii) (5marks)

9. State three adaptations of alveolus of a mammal for gaseous exchange (3mks)

10. Explain how Aerenchyma tissue are adapted to their functions (2marks)

11. Describe how gaseous exchange occurs in terrestrial plants. (13 marks)

12. The diagram below shows how gaseous exchange occurs across the gills of a fish.

According to the diagram water and blood flows in opposite directions across the gills.

(a)Give the term used to describe this flow. (1mark)

(b)Explain the advantage of the above flow named in (a) above. 2marks)

(c)What differences would be observed if water and blood flow across the gills in the same direction. (2marks)

13. (a) Name the site of gaseous exchange in mammals. (1mk)

(b) State one characteristics of the site named in (a) above. (1mk)

14(a) Describe three adaptations of a respiratory surface. (6mks)

(b)Describe the mechanism of gaseous exchange in a mammal. (14mks)

15 a) State one function of cilia in organisms. (1 mark)

b) Name two parts of the human body that have cilia. (2 marks)

16. How is the alveolus of a mammal adapted for gaseous exchange? (3 marks)

17. The following diagram represents the internal structure of a leaf. Study it and answer the questions that follow.

(a)Name the parts marked A and E (2 marks)

(b)State the roles of parts marked B and C in plant nutrition (2 marks)

(c)Briefly describe the process of gaseous exchange between part marked D and the cells during the day

(4 marks)

18. The apparatus whose diagram is given below can be used to demonstrate the results of a physiological process that occurs in a mammal. To use the apparatus, the experiment places his mouth at the point marked X and breaths in and out gently.

(a)State the observations in the boiling tube when the experimenter

(i)Breaths in:

Boiling tube, A (2 mark)

Boiling tube, B (1 mark)

ii) Breaths out:

Boiling tube, A (1 mark)

Boiling tube, B (1 mark)

(b) What conclusions can you draw from the results of this experiment (2 marks)

19. The diagram below shows part of a mammalian respiratory system.

(a)Explain two ways in which the part labelled T is adapted to its functions. (2mks)

(b)How does the part labelled S facilitates breathing in? (2mks)

The apparatus below illustrate breathing in a mammal.

(a)Describe what happens if the rubber plug is pulled in the direction shown by the arrow. 1mk

(b)Give the parts of mammal represented by:-

(i)Capillarity tube. 1mk

(ii)Rubber plug. 1mk

KCSE-Biology

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