KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

Describe causes and methods of controlling water pollution

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN08

Describe causes and methods of controlling water pollution

answers

It is addition of substance into water that may cause harm to organisms and are disruptive to ecosystem.
The causes of water pollution include:
Industrial effluents that may be toxic chemicals which may kill the aquatic organisms. It can be controlled by treating the effluents before discharging them.
Hot water that reduces concentration of oxygen killing the animals. It is controlled by placing high penalties on factories discharging hot water.
Oil spillage from oil tankers that reduces oxygen in water, penetration of light intensity and clog feathers of marine birds. It can be controlled by regular servicing of oil tankers.
Domestic effluents that include:
Untreated sewerage that causes water borne diseases. It can be controlled by treating sewerage before being discharged.
Detergents that cause eutrophication causing reduced oxygen concentration. It is controlled by banning phosphate based detergents.
Agricultural effluents that include:
Pesticides and herbicides that have heavy metals that they may cumulates along the food chain killing the higher animals. It is controlled by use of biological control of pests.
Inorganic fertilizers that have nitrates and sulphates that cause eutrophication is controlled by use of organic fertilizers.
Silting due to soil erosion reduces penetration of light to the plants and clog respiratory surfaces of animals. It is controlled by proper methods of soil erosion and proper farming methods.

Comments

Describe the structure and functions of the various parts of the human ear

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN07

Describe the structure and functions of the various parts of the human ear

answers

The ear is an organ involved in perceiving sound and maintaining body balance and posture. It is made of the following sections
Pinna – That is funnel shaped structure made of skin and cartilage. It receives sound waves and directs them to the ear tube.
External/auditory meatus – That is a canal lined with air and wax. It allows passage of sound waves to the middle ear. The hairs and wax trap dust particles that enter the ear.
Tympanic membrane – That is a thin flexible sheet-like structure receives sound waves and pass the vibration to the ossicles.
Middle ear that is composed of Tiny bones known as ossicles – They are anvil and incus. They amplify vibration from the tympanic membrane.
Eustachian tube – That connects the ear to the nasal cavity. It balances pressure on both sides of the tympanic membrane.
Oral window – That is a thin flexible membrane that opens into the inner ear. it receives vibrations from the ossicles and passes them to the inner ear.
Inner ear that is compost of;
Vestibular apparatus- That are the semicircular canals, utricles and saccules. They help in maintenance of body balance and posture.
Cochlea – That is a coiled structure that has sensory cells for hearing. It connected to the auditory nerve that is involved in transmission of sounds to the brain

Comments

Other than sugars name two compounds that are translocated in phloem

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

Other than sugars name two compounds that are translocated in phloem

answers

Amino acids
Soluble fats/ lipids

Comments

Name the structures in phloem that are involved in the translocation of sugars

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

Name the structures in phloem that are involved in the translocation of sugars

answers

Sieve plates
Cytoplasm strands

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

In the experiment to determine the effect of ringing on the concentration of sugar in phloem a ring of bark from the stem of a tree was cut and removed. The amount of sugar in grammes per 16cm3 piece of bark above the ring was measured over a 24 hour period. Sugar was also measured in the bark of a similar stem of a tree which was not ringed. The results are shown in the table below.

(a) Using the same axes, plot a graph of the amount of sugar against time
(b) At what time was the amount of sugar highest in the
(i) Ringed stem
(ii) Normal stem?
(c) How much sugar would be in the ringed stem if it was measured at 0345hours?
(d) Give reasons why there was sugar in the stems of both trees at 06 45 hours
(e) Account for the shape of the graph for the tree with ringed stem between:
(i) 06 45 hours and 15 45 hours
(ii) 15 45 hours and 00 45 hours

answers

(b)(i) 15: 45
(ii) 12:45
(c) 0.79 + 0.02 grammes
(d) The food that had been manufactured the previous day had been converted to soluble sugars and was being translocated to other parts of the plant.
(e)0645 hours and 15 45 hours
There was low concentration of sugars early in the morning as there was little translocation
As day progresses the light intensity increases and more food is manufacture thus more translocation increasing concentration of sugars
(ii)15 45 hours and 0045 hours
The light intensity is decreasing reducing rate of photosynthesis. Less food is manufactured hence less is translocation
As it turns dark there is no photosynthesis reducing concentration of sugars translocated.

Comments

What is meant by hybrid vigour?

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

What is meant by hybrid vigour?

answer

It is when best characteristics are developed from both parents and offspring better than either parent.

Comments

What is genetic engineering?

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

What is genetic engineering?

answer

Deliberate modification of characteristics of an organism by manipulate genes and DNA by transferring genes from one organism to another

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

In maize the gene for purple colour is dominant to the gene for white colour. A pure breeding maize plant with purple grains was crossed with a heterozygous plant.
(a)
(i) Using letter G to represent the gene for purple colour, work out the genotype ratio of the offspring
(ii) State the phenotype of the offspring

answers

(ii) All purple coloured grained maize plants

Comments

State two advantages of having an exoskeleton

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN04

State two advantages of having an exoskeleton

answers

Prevents drying out of organism
Controls size of the organism
Provides protection against microbial infections and mechanical injury

Comments

State the functions of synovial fluid

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN04.

State the functions of synovial fluid

answers

It’s a slippery fluid that lubricates the joints reducing friction during movement

Comments

State the difference between ball and socket and hinge joint

22/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN04

State the difference between ball and socket and hinge joint

answers

Ball and socket joint- allow movement in all directions i.e 360
Hinge joint – Allow movement only on one plane i.e 180

Comments

Name the three type of muscles found in mammals and give an example of where each of them is found

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN04

Name the three type of muscles found in mammals and give an example of where each of them is found

annswers

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

The diagram below shows a stage during fertilization in a plant.

(i) Name the parts labeled Q, R, and S
R
S
(ii) State two functions of the pollen tube
(c) On the diagram label the micropyle

answers

(b)(i) Q – Antipodal cells
R- Polar body/ polar nucleaus
S – egg cell
(ii) Path the rough which the male gametes reach the embryo sac to enhance fertilization
(iii) Prevent other pollen grains from developing into pollen tubes hence no multiple fertilization of embryo sac

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

What is meant by the following terms
(i) Protandry
(ii) Self sterility?

answers

(i) Protandry – stamens mature and pollen grains are shed off before the stigma matures
(ii) Self sterility – Pollen grains from the anthers cannot grow on the stigma of the same flower or plant

Comments

What term is given to the condition described in (c) (i) above

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP2QN02

What term is given to the condition described in (c) (i) above

answer

Diabetes insipidus

Comments

<<Previous

Describe causes and methods of controlling water pollution

Describe causes and methods of controlling water pollution

Describe the structure and functions of the various parts of the human ear

Describe the structure and functions of the various parts of the human ear

Other than sugars name two compounds that are translocated in phloem

Other than sugars name two compounds that are translocated in phloem

Name the structures in phloem that are involved in the translocation of sugars

Name the structures in phloem that are involved in the translocation of sugars

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

K.C.S.E Biology Q & A - MODEL 2007PP2QN06

What is meant by hybrid vigour?

What is meant by hybrid vigour?

What is genetic engineering?

What is genetic engineering?

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

K.C.S.E Biology Q & A - MODEL 2007PP2QN05

State two advantages of having an exoskeleton

State two advantages of having an exoskeleton

State the functions of synovial fluid

State the functions of synovial fluid

State the difference between ball and socket and hinge joint

State the difference between ball and socket and hinge joint

Name the three type of muscles found in mammals and give an example of where each of them is found

Name the three type of muscles found in mammals and give an example of where each of them is found

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

K.C.S.E Biology Q & A - MODEL 2007PP2QN03

What term is given to the condition described in (c) (i) above

What term is given to the condition described in (c) (i) above

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