K.C.S.E Biology Q & A - MODEL 1996PP1QN 22
Describe how new plants arise by asexual reproduction
K.C.S.E Biology Q & A - MODEL 1996PP1QN 21
Explain how the mammalian skin is adapted to perform its functions
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.
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?
(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
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
(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
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
K.C.S.E Biology Q & A - MODEL 1996PP1QN 17c
How can low blood volume be brought back to normal
K.C.S.E Biology Q & A - MODEL 1996PP1QN 17b
Name the process by which the human body naturally stops Bleeding?
K.C.S.E Biology Q & A - MODEL 1996PP1QN 17a
How may excessive bleeding results in death?
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
(b) Auxins / hormones; move diffuse to the demised/ away from the light side; causing elongation/ growth on the dark sides hence bending
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.
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
K.C.S.E Biology Q & A - MODEL 1996PP1QN14b
Name two structures used for gaseous exchange in plants
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
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
K.C.S.E Biology Q & A - MODEL 1996PP1QN12
Give a reason why it is necessary for frogs to lay many eggs
To increase the chances of fertilization and survival of species
Give a reason why it is only mutation in genes of gametes that can influence evolution.
Gametes form new offspring