KNEC KCSE BIOLOGY TOPICAL QUESTIONS

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

2/7/2020

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);

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

2/7/2020

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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

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

2/7/2020

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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.

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

2/7/2020

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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;

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

2/7/2020

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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;

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Name the evidence of organic evolution exhibited by occurrence of similar amino acid molecules in a range of organisms.

2/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN14

Name the evidence of organic evolution exhibited by occurrence of similar amino acid molecules in a range of organisms.

answers

(b) comparative physiology/ biochemistry/cell biology;
Acc. Serology /comparative serology.

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Explain why fossil records as evidence of organic evolution are usually incomplete.

2/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN14

Explain why fossil records as evidence of organic evolution are usually incomplete.

answers

(a) partial/ entire decomposition of dead organisms/ organic matter;
Some parts of or entire dead organisms are eaten by scavengers;
Soft bodied organisms do not fertilize;
Destruction of parts due to natural disasters, like earthquakes/earth movements like, faulting /folding/ volcanicity/ mass movement;
Distortion of parts of an organism due to sedimentary/ faulting/folding/volcanic

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K.C.S.E Biology Q & A - MODEL 2019PP1QN10

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN10

In an investigation, students set up the apparatus below in the laboratory and made observations after 72 hours.

(a) Explain how inclusion of the following components would affect the mouse in the experiment:
(i) light
(ii) sodium hydroxide solution
(b) State why the students preferred to use a bell jar and not a tin box in the experiment.

answers

.(a) i) light enables the potted plant to photosynthesize; producing oxygen which is
Inhaled by the mouse, (sustaining it); the illuminated light can further affect /alter some photosynthesized processes in the mouse as a result of constant direct beam of light.
(ii) Absorbs carbon(iv)oxide (mainly exhaled by the mouse); while at the same time deny the plant the needed raw material, carbon (iv) oxide to photosynthesize hence suffocating the mouse/ emitting its survival / no oxygen;
(b) bell jar is transparent, allow penetration of light for the plant to photosynthesize; tin box is opaque hence does not allow photosynthesis/ could easily heat up altering the temperature inside for the mouse/ plant;

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K.C.S.E Biology Q & A - MODEL 2018PP2QN04

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2018PP2QN04

The diagram below illustrates the arrangement of bones in a human arm.

(a) Name:
(i) the type of joints formed at points H and M.
H
M
(ii) bone G
(b) Name bone J and state how it is adapted to its functions.
Name
Adaptation
(c) State one functional difference between a tendon and a ligament.

answers

a) i. H-Ball and socket (joint);
M - Gliding/planar/plane
ii. Clavicle;
b) Scapula;
Has a spine to increase surface area for muscle attachment;
It is broad/flat to increase the surface area for muscle attachment;
Forms flexible attachment above the ribs that allows movement of the arms;
Has a glenoid cavity/depression for articulation with the humerus/forming the ball and socket joint;
Has acromion for articulation with clavicle/for muscle attachment;
Has coracoid process to increase surface area for muscle attachment;
c) Ligaments hold the bones together (at a joint) while tendons attach muscles to bones;

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K.C.S.E Biology Q & A - MODEL 2018PP2QN03

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2018PP2QN03

The amount of blood flowing tough certain pans in the mammalian body at different activity levels was measured and results tabulated as Shows in the table below.

(a) Account for:
(i) the high blood flow through the cardiac and skeletal muscles during strenuous exercises.
(ii) the results obtained for the alimentary canal at rest.
(b)Name two waste materials excreted by both the skin and the kidneys.

answers

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K.C.S.E Biology Q & A - MODEL 2018PP1QN25

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2018PP1QN25

Desert kangaroo rats spend most of their time in underground burrows,
(a) Name this type of behavioral activity
(b) Explain the significance of this behaviour to the organism.

answers

(a) Aestivation;
(b) Reduced metabolic activity; hence low rate of respiration; minimizing water loss/dessication (to the environment);