KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

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

Identify the type of asexual reproduction exhibited by yeast cells

1/11/2021

Comments

a) Identify the type of asexual reproduction exhibited by yeast cells (1mk)

Budding;

b) List down the functions of the following parts; (3mks)

i) Testis

Production of the male reproductive cell/gamete/sperm;
Production of androgens/male hormones.

ii) Fallopian tube

Fertilization takes place here/where fertilization occurs;
Passage of the female gamete/fertilized ovum to the uterus.

iii) Urethra

Passage of urine/sperms/semen;

Comments

State the importance of breathing through the nose than through the mouth.

1/11/2021

Comments

State the importance of breathing through the nose than through the mouth. (2mks)

Nasal cavity has hairs and mucus that trap solid particles and dust;
Nasal cavity is well supplied with blood that warms and moistens incoming air.
Has olfactory cells that are sensitive to smell;

Comments

A passenger was involved in a road accident. He couldn’t move his limbs and neck. Which part of the brain was affected?

1/11/2021

Comments

(a) A passenger was involved in a road accident. He couldn’t move his limbs and neck. Which part of the brain was affected? (1mk)

Cerebrum;

(b) (i)State two functions of cerebrospinal fluid. (2mks)

Nourishes the brain cells/supplies nutrients/removes metabolic wastes from brain cells.
Acts as a shock absorbs to the CNS

Comments

State how the following parts of the mammalian ear are adapted to their functions.

1/11/2021

Comments

State how the following parts of the mammalian ear are adapted to their functions. (3mks)

(i) Pinna

Funnel shaped to collect and concentrate sound waves into the external auditory meatus;
In some animals its large and when flapped creates air currents lining about cooling effect to the animals;

(ii) Eardrum

Its thin and flexible to enable transformation of sound waves into vibrations

(ii) Cochlea

It’s coiled to offer a large surface area for the attachment of the sensory cells.
Has numerous sensory cells to perceive sound vibrations.
Has thin membrane that vibrates more increasing the intensity of sound vibrations;
It’s filled with a fluid to enhance transmission of sound waves in it.

Comments

Name two types of active immunity

1/11/2021

Comments

Name two types of active immunity (2mks)

Natural active immunity;
Artificial active immunity;

Comments

Form two students set up an experiment as shown in the diagram below;

1/11/2021

Comments

Form two students set up an experiment as shown in the diagram below;

(a) Which process was being investigated? (1mk)

Anaerobic respiration
Rej: Respiration alone

(b) Why was it necessary to boil the glucose solution? (1mk)

To expel all the dissolved oxygen;

(c) Write a word equation representing the chemical reaction taking place above in the boiling tube (1mk)

Comments

Study the bones below and answer the questions that follow;

1/11/2021

Comments

Study the bones below and answer the questions that follow;

(a) Identify the function of the part labeled Q (1mk)

Offers a large surface area for muscle attachment

(b) Name the bone that circulates with the bone above at the proximal end (1mk)

Humerus;
Rej: Humerous or other wrong spellings for humerus

(c) List down two types of support tissue in plants (2mks)

Cellulose
Colenchyma tissue.
Selerenchyma tissue.
lignified xylem and tracheids;

Comments

<<Previous

​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)

​a) Identify the type of asexual reproduction exhibited by yeast cells (1mk)

​b) List down the functions of the following parts; (3mks)

i) Testis

​ii) Fallopian tube

​iii) Urethra

State the importance of breathing through the nose than through the mouth. (2mks)

​(a) A passenger was involved in a road accident. He couldn’t move his limbs and neck. Which part of the brain was affected? (1mk)

(b) (i)State two functions of cerebrospinal fluid. (2mks)

​State how the following parts of the mammalian ear are adapted to their functions. (3mks)

​(i) Pinna

(ii) Eardrum

​(ii) Cochlea

Name two types of active immunity (2mks) ​

​(a) Which process was being investigated? (1mk)

(b) Why was it necessary to boil the glucose solution? (1mk)

(c) Write a word equation representing the chemical reaction taking place above in the boiling tube (1mk)

(a) Identify the function of the part labeled Q (1mk)

​(b) Name the bone that circulates with the bone above at the proximal end (1mk)

(c) List down two types of support tissue in plants (2mks)

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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)

a) Identify the type of asexual reproduction exhibited by yeast cells (1mk)

b) List down the functions of the following parts; (3mks)

ii) Fallopian tube

iii) Urethra

(a) A passenger was involved in a road accident. He couldn’t move his limbs and neck. Which part of the brain was affected? (1mk)

State how the following parts of the mammalian ear are adapted to their functions. (3mks)

(i) Pinna

(ii) Cochlea

Name two types of active immunity (2mks)

(a) Which process was being investigated? (1mk)

(b) Name the bone that circulates with the bone above at the proximal end (1mk)