KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

It has a selective permeable Bowman's capsule that only allows food substances and food products to pass through but prevents the passage of plasma proteins and blood cells.
The afferent arteriole is highly branched in the glomerulus and this provides a larger surface area for blood to flow in the kidney for filtration.
The efferent arteriole have a narrower lumen than the afferent arteriole and this builds up higher pressure necessary for ultra-filtration.

Adaptations for reabsorption

Kidney tubules are long and coiled and this provides a larger surface area for reabsorption and more time is allowed for reabsorption of the useful products.
The kidney tubules are highly vascularised to ensure constant removal of reabsorbed substances hence creating more room for further reabsorption.
The microvilli on the inner surface of epithelial lining of proximal convoluted tubules provide a larger surface area for reabsorption.
Cells lining the kidney tubules/proximal convoluted tubule have numerous mitochondria which provide energy for active reabsorption of glucose, amino acids, vitamins and mineral salts.
The loop of henle is U -shaped and this creates a multiple counter current system for efficient reabsorption of substances

Comments

State three ways in which blood capillaries are structurally adapted to their functions.

18/3/2022

Comments

K.C.S.E Biology Q & A - MODEL 2018PP1QN08

State three ways in which blood capillaries are structurally adapted to their functions.

Numerous to increase surface area through which materials diffuse;
Thin/one-cell thick/single cell epithelium/endothelium for faster diffusion;
Lined with a single cell epithelium for faster diffusion;
Are selectively permeable for passage of materials;
Narrow lumen to maintain pressure;

Comments

Explain structure and functions of the human eye.

4/11/2021

Comments

Explain structure and functions of the human eye. (20mks)

Conjuctiva - Protects eyeball from mechanical injury.
Cornea - Allows light to pass through
Iris - Controls amount of light passing through
Forea - Where image is formed
Sctera - Protect the eye ball; give it shape
Choroid - Absorbs stray lights
Provide nourishment to the eye.
Aqueous/vitreous humour - refract light into the eye towards retina maintain shape of eye ball.
Ciliary body - Controls curvature of the lens.
Rods - Perceive light of low intensity
Cones - Perceives light of high intensity.

Comments

Describe the mechanism of inhalation in man

4/11/2021

Comments

(a) Describe the mechanism of inhalation in man. (10mks)

External intercostals muscles contract; internal intercostals muscle relax, Rib cage move outwards; and upwards; Diaphragm muscles contract, Diaphragm flatten; volume in thoraci cavity increases; pressure reduces.
Atmospheric air enters the lungs; inflate (correct sequence to be followed)

(b) Using photosynthesis theory explain the mechanics of opening of stomata. (10mks)

Guard cells have chloroplast which photosynthesis in the presence of light, to form sugar, the osmotic pressure of guard cell increases; water move from neighbouring cells into guard cells being thicker than outer walls. Causes the outer wall to stretch more resulting guard cells budging outwards.

Comments

A group of students carried out a study of the population growth of flour weevils.

4/11/2021

Comments

A group of students carried out a study of the population growth of flour weevils. They put 16 grams of maize flour into two equal boxes K and L respective . They then introduced equal numbers of weevils into the boxes. The boxes were kept under similar environmental conditions. The weevils were counted at intervals and the results recorded in the table below.

(a) Using a suitable scale ,draw two graphs on the same axes from the results in the table.
Plot approximate number of weevils present on the Y – axis( Use graph paper provided) (8mks)

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

K - 555
L - 1020

(c) (i) On what day was the population of weevils in K 580. (1mk)

86th Day

(ii) Between which days was the population difference greatest . (1mk)

100 - 120

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

Increase in population; because there is adequate food; the number of reproducing individuals is increasing; wastes products have not accumulated to toxic levels.

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

Diseases
Lack of food
Death rate equal to birth rate.

Comments

Explain why certain bacteria and other pathogens become resistance to drugs after some time

3/11/2021

Comments

(a) What is mutation? (2mks)

Mutation is a sudden/spontaneous change; in the genetic make up of an organism

(b) Explain why certain bacteria and other pathogens become resistance to drugs after some time. (2mks)

bacterial that survive the drug will undergo mutation: to produce bacteria which are resistance to the prevailing condition/drug. (2mks)

(c) Work out a cross between a Haemophiliac man married to a carrier woman for Haemophilia.
Use letter h to represent genes. (3mks)

(d) State the phenotypic ratio of the children. (1mk)

Phenotypic ratio :

1 male normal
1 male haemophiliac
1 female haemophiliac
1 female carrier

1 male normal:
1 male haemophiliac:
1 female haemophiliac:
1 female carrier: (1mk)

Comments

The diagram below represents female reproductive system;

3/11/2021

Comments

The diagram below represents female reproductive system;

(a) Name the part labelled ;A ,B ,C and D. (4mks)

A:

ovary

B:

Oviduct/fallopian tube

C:

Uterus/uterine wall

D:

D - Cervix

(b) State two functions of structure A. (2mks)

Produce ova femme hormones/ Estrogen and progesterone.

(c) How is part C adapted to its functions? (1mk)

Highly vascularized tosupply nutrients to foetus/drain away excretory wastes.
Inner wall lined with Endometrium for implantation of fertilized egg/zygote.
Muscular for peristalisis to expel menses during menstruation/parturition
Great capacity to expand during gestation to accommodation developing foetus

(d) Of what significance is part E to reproduction? (1mk)

Copulation/Achieve orgasm in Human male followed by ejaculation birth canal

Comments

The diagram below represents a maize seedling.

3/11/2021

Comments

The diagram below represents a maize seedling.

(a) Name the parts labeled P and Q. (2mks)

P:

Coleoptile/plumule sheath;

Q:

Root

(b) State the function of the part labeled R. (1mk)

Storage of food/enzyme/to provide food to the seedling

(c) Give three adaptations of the structure labeled S to its functions. (3mrks)

Elongated to increase surface area for absorption of water ‘b and c’ tied to ‘a’
Has many mitochondria for active transport
Has thin wall/thin walled for paste absorption of water and mineral salts

(d) What is the role of air in germination of the above seedlings? (2mks)

Air contains oxygen for respiration/oxidation to produce energy.

Comments

A group of students set up an experiment to investigate a certain physiological process. The set up was as shown in the diagram below.

3/11/2021

Comments

A group of students set up an experiment to investigate a certain physiological process. The set up
was as shown in the diagram below.

(a) What physiological process was being investigated? (1mk)

Osmosis

(b) (i) State two major observation that was made after some time. (2mks)

Distilled in the Irish potato would reduce in level; (1mk)
Level of concentrated salt solution would increase in the Petri dish(2mks)

(ii) Account for the above observation in b (i) above. (4mks)

Concentrated salt solution in the Petri-dish has higher osmotic pressure than the cells of the Irish potato; these cells lost water to the salt solution by osmosis; these cells become more concentrated and drew water from the neighbouring cells; this process continued until the cells in contact with water in the potato drew it up. (4mks)

(c) State the significance of the biological process involved in the experiment. (1mk)

Support in herbaceous plants
Absorption of water
Opening and closing of stomata
Movement and water between plants
Feeding in sectivorous plants
Folding of leaves of mimosa pudica when touched

Comments

The diagram below shows a specialized cell from a human being.

3/11/2021

Comments

The diagram below shows a specialized cell from a human being.

(a) Identify the cell. (1mk)

Sperm cell/spermatozoon;

(b) Name the parts labelled A,B, and C. (3mks)

A:

A crosome;

B:

Nucleus

C:

Mitochondria

(c) State the functions of the part labeled D. (1mk)

Propels the sperm forward

(d) A student observed cells under a microscope and counted six (6) cells a cross the diameter of view. The diameter of field of view was found to be 1.25mm. Calculate the length of one of the cells observed. ( Answer in micrometer). (3mks)

Comments

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​BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 2 MODEL26092022001

​BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 3 MODEL26092022001

​BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 1 MODEL26092022001

QUESTION PAPER

MARKING SCHEME

​​Explain how the kidney is adapted to its function

​Adaptations for ultra-filtration

​Adaptations for reabsorption

State three ways in which blood capillaries are structurally adapted to their functions.

​Explain structure and functions of the human eye. (20mks)

​(a) Describe the mechanism of inhalation in man. (10mks)

​(b) Using photosynthesis theory explain the mechanics of opening of stomata. (10mks)

(a) Using a suitable scale ,draw two graphs on the same axes from the results in the table. Plot approximate number of weevils present on the Y – axis( Use graph paper provided) (8mks)

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

​(c) (i) On what day was the population of weevils in K 580. (1mk)

​(ii) Between which days was the population difference greatest . (1mk)

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

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

​(a) What is mutation? (2mks)

(b) Explain why certain bacteria and other pathogens become resistance to drugs after some time. (2mks)

​(c) Work out a cross between a Haemophiliac man married to a carrier woman for Haemophilia. Use letter h to represent genes. (3mks)

​(d) State the phenotypic ratio of the children. (1mk)

​The diagram below represents female reproductive system;

(a) Name the part labelled ;A ,B ,C and D. (4mks)

​A:

B:

C:

D:

​(b) State two functions of structure A. (2mks)

(c) How is part C adapted to its functions? (1mk)

​(d) Of what significance is part E to reproduction? (1mk)

​The diagram below represents a maize seedling.

​(a) Name the parts labeled P and Q. (2mks)

​P:

​Q:

​(b) State the function of the part labeled R. (1mk)

​(c) Give three adaptations of the structure labeled S to its functions. (3mrks)

​(d) What is the role of air in germination of the above seedlings? (2mks)

​A group of students set up an experiment to investigate a certain physiological process. The set up was as shown in the diagram below.

​(a) What physiological process was being investigated? (1mk)

​(b) (i) State two major observation that was made after some time. (2mks)

​(ii) Account for the above observation in b (i) above. (4mks)

​(c) State the significance of the biological process involved in the experiment. (1mk)

​The diagram below shows a specialized cell from a human being.

​(a) Identify the cell. (1mk)

​(b) Name the parts labelled A,B, and C. (3mks)

A:

B:

C:

​(c) State the functions of the part labeled D. (1mk)

(d) A student observed cells under a microscope and counted six (6) cells a cross the diameter of view. The diameter of field of view was found to be 1.25mm. Calculate the length of one of the cells observed. ( Answer in micrometer). (3mks)

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BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 2 MODEL26092022001

BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 3 MODEL26092022001

BIOLOGY REVISION KITS FORM 3 TERM 1 PAPER 1 MODEL26092022001

Explain how the kidney is adapted to its function

Adaptations for ultra-filtration

Adaptations for reabsorption

Explain structure and functions of the human eye. (20mks)

(a) Describe the mechanism of inhalation in man. (10mks)

(b) Using photosynthesis theory explain the mechanics of opening of stomata. (10mks)

(a) Using a suitable scale ,draw two graphs on the same axes from the results in the table.
Plot approximate number of weevils present on the Y – axis( Use graph paper provided) (8mks)

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

(c) (i) On what day was the population of weevils in K 580. (1mk)

(ii) Between which days was the population difference greatest . (1mk)

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

(a) What is mutation? (2mks)

(c) Work out a cross between a Haemophiliac man married to a carrier woman for Haemophilia.
Use letter h to represent genes. (3mks)

(d) State the phenotypic ratio of the children. (1mk)

The diagram below represents female reproductive system;

A:

(b) State two functions of structure A. (2mks)

(d) Of what significance is part E to reproduction? (1mk)

The diagram below represents a maize seedling.

(a) Name the parts labeled P and Q. (2mks)

P:

Q:

(b) State the function of the part labeled R. (1mk)

(c) Give three adaptations of the structure labeled S to its functions. (3mrks)

(d) What is the role of air in germination of the above seedlings? (2mks)

A group of students set up an experiment to investigate a certain physiological process. The set up
was as shown in the diagram below.

(a) What physiological process was being investigated? (1mk)

(b) (i) State two major observation that was made after some time. (2mks)

(ii) Account for the above observation in b (i) above. (4mks)

(c) State the significance of the biological process involved in the experiment. (1mk)

The diagram below shows a specialized cell from a human being.

(a) Identify the cell. (1mk)

(b) Name the parts labelled A,B, and C. (3mks)

(c) State the functions of the part labeled D. (1mk)