KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

Describe how new plants arise by asexual reproduction

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 22

Describe how new plants arise by asexual reproduction

ANSWERS

Lower plants/example Bryophyta/pterophyta; produces spores which develops to new plants; budding an overgrowth arises from plant drop off; and develops into a new plant; common in lower plants yeast.
Fragmentation – e.g Spirogyra; breaks off and grows into a new plant
Vegetative propagation: common in higher plants involves growth of new plants from buds/bubils
Root stem/ tubers/ leaves: possesses buds; which develops to new plants
Corns; have terminal buds that grows vertically and produce a new plant
Runners; have lateral buds that produce new plants

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Explain how the mammalian skin is adapted to perform its functions

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 21

Explain how the mammalian skin is adapted to perform its functions

ANSWERS

The cornified layer is made up of dead cells, that prevent entry of bacteria and prevent physical damage; melanin protects the body against U-V variation; sebaceous glands produce a chemical/ ring substance which is of blood vessel; which when the body temperature is high dilate and heat is lost or when body temp is low blood vessels constrict.
And heat is retained. Hair when it is called, stands and traps air between themselves; to retain heat/ stop heat loss or when it is hot hair lies flat close on the skin; so does not trap air, and therefore heat is retained and sweat is lost; the skin has sweat glands which produces sweat;
sweat evaporates thus cooling the body.

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 20

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 20

A culture of bacteria was incubated in nutrient agar at 350C. Samples were taken at intervals in order to estimate the number of bacteria in the population. The data obtained is shown in the graph below.

(a) When was the pollution of bacteria 350 million
(b) Account for the shape of the graph between
(i) A and B
(ii) B and C
(iii) C and D
(c) Give three reasons for the shape of the curve between D and E
(d) (i) Suggest what would happen to the population of the bacteria if the temperature was lowered to 00 after incubating for 12 hours.
(ii) Give a reason for your answer in (d) (i) above
(e) Give three reasons why it is important to control human population growth rate in Kenya?

ANSWERS

(a) 10 HRC and 31 HRC
(b) (i) A and B The number of bacteria dividing are few: bacteria are adjusting conditions: few are dying therefore high increase in population
(ii) B and C More cells are dividing due to suitable environment/ favorable conditions; few are dying; therefore high increase in population
(iii) C and D No population change; number produced is equal to number dying.
(c) Accumulation of toxic wastes; that kills bacteria; depletion of nutrients leading to competition of space.
(d) (i) The population will remain the same
(ii) Temperature not conclusive for division
(e) Food to be sufficient for population
Social amenities/ education; health services

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 19

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 19

The diagram below represents then pathways of water from the soil into the plant.

(a) Name the structures labeled K and L.
(b) Explain how water from the soil reaches the structure labeled L.
(c) Name the process by which mineral salts enter into the plant

ANSWERS

(a) K- Root hair
L- Xylem vessel
(b) Water moves from the soil into the root hair by osmosis; because concentration of cell sap is higher than water in the soil; the cell sap in the root hair is diluted, thus making it less concentrated than neighboring cell; therefore water moves into the neighboring cell; it is actively secreted into structure L.
(c) Active transport/ diffusion

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 18

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 18

In an experiment black mice were crossed and the offspring were back and brown. The gene for black colour is dominant over that of brown colour.
Using letter B to represent the gene for black colour and b to represent the gene for brown colour
(a) Work out the genotypes of the F1 generation
(b) What is the phenotype ration of the spring

answers

(b) 3 black 1 brown

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How can low blood volume be brought back to normal

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 17c

How can low blood volume be brought back to normal

answers

Transfusion; taking fluids) eating iron rich food stuff/ taking iron tablets.

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Name the process by which the human body naturally stops Bleeding?

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 17b

Name the process by which the human body naturally stops Bleeding?

answers

Blood clotting

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How may excessive bleeding results in death?

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 17a

How may excessive bleeding results in death?

answers

Anaemia/ low blood volume/ loss of iron/ low red blood cells/ low haemoglobin; leading to low oxygen; loss of nutrients and dehydrations.

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K.C.S.E Biology Q & A - MODEL 1996PP1QN16

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN 16

A shoot of seedling exposed to light on one side bends towards the source of light as it grows
(a) Name the response exhibited by the shoot of the seedling
(b) Explain how the bending towards the source of light occurs

answers

(a) Phototropism
(b) Auxins / hormones; move diffuse to the demised/ away from the light side; causing elongation/ growth on the dark sides hence bending

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K.C.S.E Biology Q & A - MODEL 1996PP1QN15

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN15

To estimate the population size of crabs in a certain lagoon, traps were laid at random. 400 crabs were caught, marked and released back into the lagoon. Four days later, traps were laid again and crabs were caught. Out of the 374 crabs, 80 were found to be marked.

(a) calculate the population size of the crabs in the lagoon using the formula below

Where N = Total population of crabs in the lagoon
n = Total number of crabs in the second catch
M = Number of marked crabs during the first
m= Number of marked crabs in the second catch

(b) State two assumptions that were made during the investigation
(c) What is the name given to this method of estimating the population size

ANSWERS

(b) There was even distribution of crabs;
No movement in and out of regions; no migration;
There was random distribution of errors after the first capture.
(c) Capture/ recapture; capture release recapture.

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Name two structures used for gaseous exchange in plants

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN14b

Name two structures used for gaseous exchange in plants

answers

Stomata pores / stomata; cuticle

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Describe the path taken by carbon dioxide released from the tissue of an insect to the atmosphere

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN14

Describe the path taken by carbon dioxide released from the tissue of an insect to the atmosphere

answers

CO2 diffuses into tracheoles follows the trachea; not through spiracles

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K.C.S.E Biology Q & A - MODEL 1996PP1QN13

14/6/2020

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The diagram below shows a set – up that was used to demonstrate Fermentation

Glucose solution was boiled and oil added on top of it. The glucose solution was then allowed to cool before suspension.
(a) Why was the glucose solution boiled before adding the yeast Suspension?
(b) What was the importance of cooling the glucose solution before adding the yeast suspension?
(c) What was the use of oil in the experiment?
(d) What observation would be made in test tube B at the end of the experiment?
(e) Suggest a control for this experiment

answers

(a) Drive out oxygen / air
(b)Avoid killing yeast cells/ denaturing enzymes in yeast
(c) To prevent air from getting into the glucose and yeast Suspension
(d) Limewater turns milky
(e) Used boiled yeast on glucose

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Give a reason why it is necessary for frogs to lay many eggs

14/6/2020

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K.C.S.E Biology Q & A - MODEL 1996PP1QN12

Give a reason why it is necessary for frogs to lay many eggs

ANSWERS

To increase the chances of fertilization and survival of species

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K.C.S.E Biology Q & A - MODEL 1996PP1QN11

1/6/2020

Comments

Give a reason why it is only mutation in genes of gametes that can influence evolution.

ANSWERS

Gametes form new offspring

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Describe how new plants arise by asexual reproduction

Describe how new plants arise by asexual reproduction

Explain how the mammalian skin is adapted to perform its functions

Explain how the mammalian skin is adapted to perform its functions

K.C.S.E Biology Q & A - MODEL 1996PP1QN 20

K.C.S.E Biology Q & A - MODEL 1996PP1QN 20

K.C.S.E Biology Q & A - MODEL 1996PP1QN 19

K.C.S.E Biology Q & A - MODEL 1996PP1QN 19

K.C.S.E Biology Q & A - MODEL 1996PP1QN 18

K.C.S.E Biology Q & A - MODEL 1996PP1QN 18

How can low blood volume be brought back to normal

How can low blood volume be brought back to normal

Name the process by which the human body naturally stops Bleeding?

Name the process by which the human body naturally stops Bleeding?

How may excessive bleeding results in death?

How may excessive bleeding results in death?

K.C.S.E Biology Q & A - MODEL 1996PP1QN16

K.C.S.E Biology Q & A - MODEL 1996PP1QN 16

K.C.S.E Biology Q & A - MODEL 1996PP1QN15

K.C.S.E Biology Q & A - MODEL 1996PP1QN15

Name two structures used for gaseous exchange in plants

Name two structures used for gaseous exchange in plants

Describe the path taken by carbon dioxide released from the tissue of an insect to the atmosphere

Describe the path taken by carbon dioxide released from the tissue of an insect to the atmosphere

K.C.S.E Biology Q & A - MODEL 1996PP1QN13

Give a reason why it is necessary for frogs to lay many eggs

Give a reason why it is necessary for frogs to lay many eggs

K.C.S.E Biology Q & A - MODEL 1996PP1QN11

Give a reason why it is only mutation in genes of gametes that can influence evolution.

Gametes form new offspring

TOPICS

Form 2

Form 3

Form 4

Archives

Categories

Describe how new plants arise by asexual reproduction

Explain how the mammalian skin is adapted to perform its functions

K.C.S.E Biology Q & A - MODEL 1996PP1QN 20

K.C.S.E Biology Q & A - MODEL 1996PP1QN 19

K.C.S.E Biology Q & A - MODEL 1996PP1QN 18

How can low blood volume be brought back to normal

Name the process by which the human body naturally stops Bleeding?

How may excessive bleeding results in death?

K.C.S.E Biology Q & A - MODEL 1996PP1QN 16

K.C.S.E Biology Q & A - MODEL 1996PP1QN15

Name two structures used for gaseous exchange in plants

Describe the path taken by carbon dioxide released from the tissue of an insect to the atmosphere

Give a reason why it is necessary for frogs to lay many eggs

​Give a reason why it is only mutation in genes of gametes that can influence evolution.

Gametes form new offspring

TOPICS

Form 2

Form 3

Form 4

Archives

Categories

Give a reason why it is only mutation in genes of gametes that can influence evolution.