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

Name the part of a bean that elongates to bring about epigeal germination

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN19

Name the part of a bean that elongates to bring about epigeal germination

ANSWER

Hypocotyl

Comments

State two environmental conditions that can cause seed dormancy

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN19

State two environmental conditions that can cause seed dormancy

ANSWERS

absence of water (moisture)
Unsuitable temperature
Lack of oxygen
Lack of light

Comments

State two disadvantages of sexual reproduction in animals

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN18

State two disadvantages of sexual reproduction in animals

ANSWERS

Harmful characteristics from the parents may be passed on the offsprings
Takes a longer time
Few offsprings are produced at a time

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN17

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN17

The diagram below represents a stage during cell division

(a) (i) Identify the stage of cell division
(ii) Give three reasons for your answer in (a) (i) above
(b) Name the structures labeled M

ANSWERS

(a) (i) Anaphase 1
(i) Homologous chromosomes separates at the equator
(ii) Chromosomes start migrating to opposite poles
(iii) Sister chromatids attached at the centromere
(b) Spindle fibres

Comments

State two ways in which schritosoma species is adapted to parasitic mode of life

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN16

State two ways in which schritosoma species is adapted to parasitic mode of life

ANSWERS

Produce large number of eggs for increased survival
Produce enzymes to digest human skin when penetrating
Can withstand low oxygen concentration
Have hooks – like structures to attach to the intestinal walls

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN15

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN15

Name a method that could be used to estimate the population size of the following organisms
(i) Fish in a pond
(ii) Black jack in a garden

ANSWERS

(i) Capture and recapture method
(ii) Line transect

Comments

Distinguish between population and community

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN15

Distinguish between population and community

ANSWERS

Population – It is all members of a given species in particular habitat at a particular time.
Community-all organisms belonging to different species interact in the same habitat.

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN14

21/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2007PP1QN14

What is the meaning of the terms
(i) Homeostatic
(ii) Osmoregulation?

ANSWERS

maintenance of a concentration of water and salts ion the body fluid.
maintenance by an organism of an internal balance between water and dissolved materials regardless of environmental conditions.

Comments

K.C.S.E Biology Q & A - MODEL 2006PP2QN05

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP2QN05

The diagram below represents human foetus in a uterus.

a) Name the part labeled S.
b) i) Name the types of blood vessels found in the structure labeled Q.
ii) State the differences in composition of blood found in the vessels named in (b)(i) above.
c) Name two features that enable the structure labeled P carry out its function.
d) State the role of the part labeled R

answers

(a) Chorion
(b) (i) Arteries; veins
(ii) More food nutrients; more oxygen in veins less food nutrients more excretory products in arteries
(c) Highly vascular zed; large surface area
Presence of secretory cells
(d) Cushion/ absorb shock

Comments

Give three reasons for loss of energy from one trophic level to another in the food chain.

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP2QN03

Give three reasons for loss of energy from one trophic level to another in the food chain.

answers

Insufficient utilization of food resource/ wastage
Through respiration
Though excretion

Comments

Distinguish between pyramid of numbers and pyramid of biomass.

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP2QN03

Distinguish between pyramid of numbers and pyramid of biomass.

answers

Pyramid of numbers is a diagrammatic representation of the number of organism, at each trophic level in a food chain; While biomass is a diagrammatic representation of dry weight organism at each trophic level in a food chain.

Comments

K.C.S.E Biology Q & A - MODEL 2006PP1QN26

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP1QN26

The chart below represents a simplified nitrogen cycle.

What is represented by X,Y, and Z?

answers

X- Denitrifying bacteria/ denitrification
Y- Animals/ Herbivores; accept primary consumers
Z- Nitrogen fixing bacteria ( in soil) accept Azotobacter.

Comments

Give three advantages of cross pollination.

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP1QN19

Give three advantages of cross pollination.

answers

Increases variety;
Hybrid vigour/ heterosis
Resistance of disease/ drought/ dry climate/ unfavorable environmental conditions/ Frost; E.g. resistance to virus, fungi, bacterial diseases of pest.

Comments

Why is oxygen necessary in the germination of seeds?

19/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2006PP1QN14

Why is oxygen necessary in the germination of seeds?

answer

Required in aerobic respiration/ oxidation; to release energy from food reserve for germination;

Comments

<<Previous

Describe causes and methods of controlling water pollution

Describe causes and methods of controlling water pollution

Name the part of a bean that elongates to bring about epigeal germination

Name the part of a bean that elongates to bring about epigeal germination

State two environmental conditions that can cause seed dormancy

State two environmental conditions that can cause seed dormancy

State two disadvantages of sexual reproduction in animals

State two disadvantages of sexual reproduction in animals

K.C.S.E Biology Q & A - MODEL 2007PP1QN17

K.C.S.E Biology Q & A - MODEL 2007PP1QN17

State two ways in which schritosoma species is adapted to parasitic mode of life

State two ways in which schritosoma species is adapted to parasitic mode of life

K.C.S.E Biology Q & A - MODEL 2007PP1QN15

K.C.S.E Biology Q & A - MODEL 2007PP1QN15

Distinguish between population and community

Distinguish between population and community

K.C.S.E Biology Q & A - MODEL 2007PP1QN14

K.C.S.E Biology Q & A - MODEL 2007PP1QN14

K.C.S.E Biology Q & A - MODEL 2006PP2QN05

K.C.S.E Biology Q & A - MODEL 2006PP2QN05

Give three reasons for loss of energy from one trophic level to another in the food chain.

Give three reasons for loss of energy from one trophic level to another in the food chain.

Distinguish between pyramid of numbers and pyramid of biomass.

Distinguish between pyramid of numbers and pyramid of biomass.

K.C.S.E Biology Q & A - MODEL 2006PP1QN26

K.C.S.E Biology Q & A - MODEL 2006PP1QN26

Give three advantages of cross pollination.

Give three advantages of cross pollination.

Why is oxygen necessary in the germination of seeds?

Why is oxygen necessary in the germination of seeds?

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