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

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

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

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

What are the effects of releasing excess nutrients into lake Naivasha by the nearby flowers farms?

1/11/2021

Comments

What are the effects of releasing excess nutrients into lake Naivasha by the nearby flowers farms? (3mks)

Oxygen depletion due to excessive growth of aquatic plants leading to suffocation and death of aquatic animals;
Entrophication hinder light penetration affecting photosynthesis in submerged hydrophytes;
Cause water surface blockage affecting navigation/fishing.

Comments

Distinguish between homologous structures and analogous structures

31/10/2021

Comments

a) Distinguish between homologous structures and analogous structures (2mks)

Homologous structures have a similar embryonic origin but modified to perform different function;
Analogous structures have different embryonic origin but modified to perform similar function;

b) State a major shortcoming in Jean Baptiste de Lamarck’s theory of evolution (1mk)

That a phenotypically acquired characteristics can be transmitted to the offspring by their parents;

Comments

Define the term allele, Differentiate between a dominant gene and a recessive gene

30/10/2021

Comments

(a) Define the term allele (1mk)

Alternative forms of a gene controlling a particular characteristic

(b) Differentiate between a dominant gene and a recessive gene (2mks)

A dominant gene expresses itself in both its homozygous and heterozygous states; while a recessive gene can only express itself in homozygous state.

Comments

Response and Co-Ordination Questions and Answers

13/11/2020

1. 1989 Q2 P1
State one structural and one functional difference between motor and sensory neurons.

2. 1990 Q15 P1
(a) How are the structures of the human eye adapted to their function?

Support and Movement in Plants and Animals Questions and Answers

13/11/2020

1. 1989 Q6 P1
The diagram below represents a mammalian bone

(a)    State the functions labelled K and L
(b)   State the region of the body in which the bone is found
2.      1991 Q1 P1
State two ways in which skeletal muscle fibers are adapted to their functions
3.      1991 Q5 P1
The diagram below shows the arrangement of bones and muscles in a human arm

K.C.S.E Biology Q & A - MODEL 2019PP2QN05

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN05

A person accidentally touches a hot pan and responds as illustrated in the diagram below.

(a) Explain how the response illustrated above occurs.
(b) Explain how auxins are utilised as selective weed killers in agriculture.

answers

(a) The stimulus /heat/pain is detected by temperature/pain receptor( Thermo receptors) in the skin/dermis; An impulse is generated; impulse is transmitted along a sensory neurone to the CNS/spinal cord; (chemical) transmission across synapse to relay neurone; Across a synapse to motor neurone; across a synapse to biceps muscles,/effector via motor neurone; muscles/effectors contracts; (hand moves away). This is known as (simple reflex action);
Stimulus/pain/temperature detector
Receptor-impulse-sensory neurone-synapse-relay neurone (CNS)-synapse-motor neurone- synapse-biceps-control.
(b) Selective weed killer contains auxins which are absorbed by the weeds (than desired/ beneficial plants); making the weeds to grow abnormally/accelerated die out; (weed of the beneficial plants);

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN04

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN04

In cats, the gene for fur colour is sex-linked. Letter G represents the gene for ginger fur colour while letter B represents the gene for black fur colour in a given cat species. These genes are co-dominant. Heterozygous females have ginger and black patches of fur and their phenotype is described as tortoise-shell.

(a) With reference to the information given above, what is meant by the term co-dominance?
(b) Explain why male cats with a tortoise-shell phenotype do not usually occur.
(c) A tortoise-shell female was crossed with a black male. Determine the genotypes and phenotypes of the offspring.

answers

Comments

K.C.S.E Biology Q & A - MODEL 2019PP1QN25

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP1QN25

State one characteristic of muscles responsible for each of the following:
(a) peristaltic movement
(b) movement of limbs

answers

(a) spindle shape
Lack striations/ not striated
Uninucleated /one nucleus

(b) striated;
Numerous mitochondrion;
Multinucleated/many nucleus
Cylindrical shaped.

Comments

Explain the evolutionary basis for the ever changing drugs for malaria treatment.

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP1QN24

Explain the evolutionary basis for the ever changing drugs for malaria treatment.

answers

malaria causing parasite over time become resistant to some malaria drugs; due to (gradually changing their genetic constitutions) mutation; which with time result in the evolution and eventual, perpetuation of the new strains of parasite hence necessitating the discovery of a more effective drug to counter the new/ emerging strains;

Comments

K.C.S.E Biology Q & A - MODEL 2019PP1QN17

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP1QN17

Below are photographs of two dogs.

Explain the possible reason for the difference in the length of their fur.

answers

Geographical distribution; made the animals adapt to survive in their environments(cold/hot), with those having thick fur being adapted to cold regions (for insulation); acc. Converse animal with short fur to adopt to hot area.
Genetic/being passed from parents to offspring's/genetic inheritance / genes being passed from parents to offspring;

Comments

<<Previous

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

​(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)

​(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

(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)

What are the effects of releasing excess nutrients into lake Naivasha by the nearby flowers farms? (3mks)

​a) Distinguish between homologous structures and analogous structures (2mks)

​b) State a major shortcoming in Jean Baptiste de Lamarck’s theory of evolution (1mk)

​(a) Define the term allele (1mk)

(b) Differentiate between a dominant gene and a recessive gene (2mks)

K.C.S.E Biology Q & A - MODEL 2019PP2QN05

K.C.S.E Biology Q & A - MODEL 2019PP2QN04

K.C.S.E Biology Q & A - MODEL 2019PP1QN25

Explain the evolutionary basis for the ever changing drugs for malaria treatment.

K.C.S.E Biology Q & A - MODEL 2019PP1QN17

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

(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)

(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

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

a) Distinguish between homologous structures and analogous structures (2mks)

b) State a major shortcoming in Jean Baptiste de Lamarck’s theory of evolution (1mk)

(a) Define the term allele (1mk)