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

K.C.S.E Biology Q & A - MODEL 2019PP2QN08

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN08

Explain the effect of increased physical activity on the following organ systems:
(a) heart
(b) lungs
(c) kidneys
(d) skin.

answers

(a) Heart
-Increased heart beat/ rate/cardiac frequency; increase blood pressure; pumping more blood to the muscles/Peripheral blood vessels; at a faster rates; supplying oxygen; Nutrients; for continued oxidation/respiration; to yield energy needed to sustain the (vigorous) contraction/relaxation of muscles during the physical activity; carbon (iv) oxide /Lactic acid/other Nitrogenous wastes/Metabolic wastes produced during the process are also eliminated/ transported to the relevant excretory organs for elimination; the wastes ,if left to accumulate Can also intoxicate/poison cells/cause muscle cramps/pain/fatigue;

(b) Lungs
-Panting /increased breathing rates; cause the lungs to expand/increase in volume to take in more air/oxygen; and deflate to expel more carbon (iv) oxide; more oxygen is taken in (during exercise) to sustain the process of muscle respiration/to produce the required energy (for constant muscle contraction and relaxation);

Kidneys

Kidneys also maintain the blood plasma pH; and osmotic balance; by elimination excess hydrogen ions(H+) that accumulate to production of Lactic acid/CO2 during the exercise;
To maintain the osmotic balance kidneys conserve sodium ions (Na+); and reabsorb water (in the kidney tubules); Leading to reduction in the volume of urine produced; During exercise the kidney tend to filter out urine releasing more in the urine;

(d) Skin
- Due to increased muscle activity during physical exercise are sweats(more); Eliminating Nitrogenous wastes/ excess water; through the skin/sweat pores) cooling the body; After (water in) sweat evaporates the increased internal body temperature also leads to dilation of superficial blood vessels (vasodilation)/ blood flowing near the skin; leading to loss of excess heat (to the atmosphere) by radiation/ convection; the hair on the skin surface also lie Flat to allow for loss of heat( to the environment) by radiation/convection;

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN07

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN07

Giving examples, describe the following interactions among organisms:
(a) predator-prey
(b) symbiosis
(c) parasitism.

answers

.(a) Predator-Prey

-Predator is an animal that hunts/kills another/ other animals(prey) for food;
-A dog and a hare; (acc. either correct examples)
Preys desire survival mechanism in their habitats not to be eaten/killed; to survive and reproduce/propagate this in linage; to this end (prey)(adaptations)
-They run faster (strong hind muscles);
-Camouflage with environments;
-Mimic the predators; (acc. some have a wider field of view/vision;)
-Some emits some chemical/smell that turn of predators;
-Others like porcupine use quills/ spikes/spines to fight off predators;
-Some have good sense of smell to detect predators; on the other hand, predators also evolve/desire means to be able to survive in such an ecosystem for instance.
-Running faster; strong jaws/long/sharp canine/talons;
-Camouflaging with the environment;
-Mimicking prey
-Sharp eyesight;
-Strong sense of smell
-Produce venom/poison that paralyze/kill prey.

(b) Symbiosis

A close (long term) association between two organisms of different species where the two mutually benefit from each other;
Example; The bacteria in the rumen/gut of herbivores; which help herbivores digest cellulose; as they are sheltered by the herbivores;
-The bacteria found in the human digestive system/gut/colon
-the bacteria are sheltered by humans;
-The bacteria aid human in synthesis of vitamin K/ B12/enzyme microbial balance;
-The nitrogen fixing bacteria on the root nodules of legumes;
-NFB benefits from shelter offered by the plant;
NFB facilitate conversion of free atmospheric Nitrogen into forms that can be readily used by the plants;

(c) Parasitism

A kind of (inter-specific) relationship/Association where one member/organism, the parasite, benefits while the other the host is harmed/loses; Also called antagonistic symbiosis)
Example;
A tick (parasite) sucking blood /Nutrients from a cow (host); making the cow to be anaemiac/skin destroyed/malnourished/transmission of diseases;
Parasite can be external/Exo-Parasite; or internal/ endo-parasite; e.g. liver fluke
Example- Liver fluke sucks blood/Nutrients from host and cause death/bodily harm on the internal Organs of the host including blocking blood vessels

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN06

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN06

The table below shows the rate of product formation for two enzymes, H and J over a range of pH values

(a) On the same axis, plot graphs of the rate of product formation against pH.
GRAPH PAPER
(b) Account for the rate of product formation for enzyme H between:
(i) pH 1.0 and 3.0
(ii) pH 3.0 and 7.0.
(c) From the graph, determine: .
(i) the pH value at which the rate of product formation of the two enzymes was the same
(ii) the value of the rate of product formation for enzymes H and J at the pH value stated in (c)(i) above
(iii) the optimum pH value for enzyme J
(d) State one variable that may lead to the change in the optimum rate of product-formation of the two enzymes.
(e) Suggest with a reason, the likely part of the human alimentary canal where enzyme H would be found.

answers

(b) (i) Rate of product formation increases with the increase in pH to the optimum then decreases;
   pH 5 is the optimum pH value for activity of enzyme H; between pH 1 and 2 enzyme H/enzyme molecules are activated; Between pH 2 and 3 enzyme H (enzyme molecules) are denatured/destroyed; (. Enzyme is inactivated/ less active for denatured
(ii) Rate of product formation (sharply) decreases with increase in pH; Enzyme H is (not formed by increase in pH hence is denatured); No product forms above pH 4.0 to 7.0; because all enzymes (enzyme molecules) are denatured;
(c) (i) 4.0
   (ii) 15.0 mg/hr
    (iii) 7.0
(d) -Temperature
-Substrate concentration;
-Enzyme concentration;
-Cofactors
-Co-enzymes
-(Enzyme) inhibitors
(e) Stomach;
Acidic medium/Low pH

Comments

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 2019PP2QN03

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN03

In an experiment, students treated seedlings as illustrated below.

(i) Account for the observations made in seedling I.
(ii) Explain the similarity in the end results made in seedlings II and III.
(iii) State the likely treatment that would make seedlings II and III respond like seedling I.

answers

(i) Positive phototropism/tip bends towards light; light causes migration of auxins (produced at the tip) to the darker sides; (of the shoot) resulting in faster division of cells/ elongation/growth on the darker /opposite side of the shoot hence bending towards light
(ii) both seedlings remain upright; ( erect) seedling II does not have tip while seedling III the tip has been covered by opaque material preventing light causing unequal distribution of auxins; . uniform/even distribution of auxins)
(iii) Fitting a gar block treated with auxins at the decapitated end of seedling II; Removing the opaque material covering the tip of seedling III/ replacing the opaque cap with a transparent one;

Comments

State one importance of irritability to living organisms.

2/7/2020

Comments

K.C.S.E Biology Q & A - MODEL 2019PP2QN03

State one importance of irritability to living organisms.

answers

(a) Enable living organisms to avoid dangerous/harmful/hash climatic environmental conditions; Enable living organisms obtain/access favourable environmental conditions (light, water, oxygen,

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)

K.C.S.E Biology Q & A - MODEL 2019PP2QN08

K.C.S.E Biology Q & A - MODEL 2019PP2QN07

K.C.S.E Biology Q & A - MODEL 2019PP2QN06

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 2019PP2QN03

State one importance of irritability to living organisms.

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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)