K.C.S.E Biology Q & A - MODEL 2015PP2QN06
The graph below shows the relative numbers of three main species of organisms in a pond.
​(a) Giving a reason for your answer, which of the species is a
(i) producer? Reason (ii) secondary consumer? Reason (b) State the depths at which each of the populations labelled L, M and N is at its optimum. L M N (c) (i) Which method may have been used to determine the population of organisms labelled N in the pond? (ii) Give a reason for your answer in (c) (j) above. (iii) State the assumptions made when using the method in (c) (i) above. (d) State two reasons why primary productivity in the pond decreases with depth. (e) Explain the ecological importance of fungi to plants. (f) Why is flooding likely to lead to a cholera outbreak?
ANSWERS
​(a) (i) Producer - M
Reason Largest in number hence source of food for the other species Abundant on the water surface to trap light for photosynthesis; (ii) Secondary consumer - N Reason - Smaller in number than L and M (b) L -1.125m; M- 0.75m; N- 2.00m; (c) (i) Capture - Recapture (method) /Capture - mark - release - recapture; (ii) Animals are highly mobile; (iii) No migration during the period of survey/study; No deaths/variation/reproductiori in population during the period; Method of marking does not affect the animal behaviour; Marked/released animals will freely mix with others in the pond; Released/marked animals will have enough time to mix with the others; There is uniform/random distribution of animals within the period. (d) Decrease in light intensity as depth increases; Decrease in temperature as depth increases; (e) Breakdown of organic materials/decompose/rot/decay of materials; to release plant nutrients; (f) Flood water may mix with human waste contaminated with cholera bacteria; The flood water may then contaminate food / water sources; The contaminated water/food causes cholera infection when ingested;
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K.C.S.E Biology Q & A - MODEL 2015PP2QN02
The diagram below illustrates the structure of the female part of a flower.
(a) Name the part labelled W.
(b) Describe what happens when the pollen tube enters the structure labelled V. (c) What do the structures labelled R and T develop into after fertilization? R T
ANSWERS
​ (a) W - ovary wall/ovary;
(b) Tip of pollen tube bursts open; one of the nuclei fuses with the egg cell nucleus; to form a diploid zygote; while the remaining male nucleus fuses with the polar nuclei; to form a triploid endosperm nucleus; (c) R - Endosperm/primary endosperm; T - testa/seed coat; K.C.S.E Biology Q & A - MODEL 2015PP1QN19
(a) Using the axes provided below, sketch a curve to illustrate the growth pattern observed in the phylum arthropoda.
(b) Explain the growth pattern observed observed in arthropods.
K.C.S.E Biology Q & A - MODEL 2015PP1QN18
The diagram below shows an experimental set-up to investigate the conditions necessary for germination. Test tube P was placed in a refrigerator while Q was left at room temperature. The set-ups were observed regularly for two weeks but no germination occurred.
​Explain the observations in P and Q.
P Q
answers
​ P - the low temperature/freezing temperature inactivated enzymes;
Q - Boiling eliminated oxygen; oil layer prevented entry of oxygen necessary for respiration during growth; K.C.S.E Biology Q & A - MODEL 2015PP1QN15
The photomicrographs below show the various stages of cell division in a certain plant.
​(a) (i) Name the type of cell division illustrated.
(ii) Give a reason for your answer in (a) (i) above. (b) (i) Name the stage of cell division labelled K. (ii) Give a reason for your answer in (b) (i) above.
answers
​(a) (i) Mitosis;
(ii) Formation of two daughter cells. (b) (i) Metaphase; (ii) Chromosomes are at the equator
K.C.S.E Biology Q & A - MODEL 2015PP1QN13
State three differences between the end products of mitosis and meiosis.K.C.S.E Biology Q & A - MODEL 2015PP1QN12
​(a) What is meant by each of the following:
(i) pyramid of biomass? (ii) pyramid of numbers’? (b) During an ecological visit to the Savanna Grassland, students were able to see lions, antelopes, vultures and pastoralists grazing their cattle. Construct a food chain with four consumer levels to illustrate the energy flow in the ecosystem. K.C.S.E Biology Q & A - MODEL 2014PP2QN06
An experiment was done to determine the uptake of nitrogen from the soil by broad bean seedlings. The experiment was done with one set of seedlings M grown in the atmosphere enriched with carbon (IV) oxide and another set up of seedlings N grown in the normal atmosphere.
The amount of nitrogen in each seedling was measured in milligrams at intervals often days. The table below shows the results obtained.
​(a) Using the same axis draw line graphs of nitrogen uptake by the two (M and N) sets of broad bean seedlings against time.
(b) Determine the rate of uptake of nitrogen in Set M between 65 and 85 days. (c) (i) What is the relationship between carbon (IV) oxide concentration in the air and nitrogen uptake? (ii) Account for the relationship in (c)(i) above. (d) (i) What would happen to the concentration of nitrogen in the seedlings in set M, if after 75 days the seedlings are transferred to a normal atmosphere. (ii) Explain your answer in (d)(i) above. (e) State three ways in which nitrogen fixation occurs.
answers
(c) (i) The higher the carbon UV) oxide content in air, the higher the nitrogen uptake and vice versa;
(ii) More Carbon (IV) oxide in the air makes the seedlings to photosynthesize more; hence more amino acids/protein; are formed in the dark stage; formation of amino acids/protein requires nitrogen; (d) (i) The concentration of nitrogen would remain constant; (ii) Despite decline in CO,; the nitrogen already absorbed/taken up by the plant will still remain: (iii) Lightning; By free-living bacteria/micro organisms; By Rhizobium (in root nodules of legumes); K.C.S.E Biology Q & A - MODEL 2014PP2QN01
​(a) State four characteristics of fruits dispersed by animals.
(b) State two roles of each of the following hormones in menstruation: (i) luteinising hormone; (ii) oestrogen.
ANSWERS
​(a)
K.C.S.E Biology Q & A - MODEL 2014PP1QN25
State two roles of luteinising hormone in human reproduction.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN18
Explain why four months after fertilisation, ovaries can be removed from a human female, without terminating pregnancy.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN18
Explain why mammalian testes are located to hang outside the body
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN06
State three roles of auxins in a plant stem.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN04
The diagram below illustrates a growing pollen tube.
​(a) Name the part labelled B.
(b) Explain the role of the parts labelled A.
ANSWERS
(a) Tube nucleus;
(b) One male nucleus fuses with the egg cell nucleus to form a zygote; The other male nucleus fuses with the polar nuclei to form the endosperm;
K.C.S.E Biology Q & A - MODEL 2014PP1QN03
State two functions of the placenta in mammals.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2014PP1QN02
What is meant by the term seed dormancy?
ANSWER
K.C.S.E Biology Q & A - MODEL 2013PP2QN06
A scientist carried out an investigation to find out the population growth of mice under laboratory conditions. Twenty young mice were placed in a cage. The results obtained from the investigation were as shown in the table below.
​(a) On the grid provided, draw a graph of the number of mice against time.
GRAPH PAPER (b) Account for the changes in mice population between (i) O to 2 months (ii) 2 to 6 months (iii) 6 to 10 months (iv) 10 to 12 months. (c) (i) Between which two months was the population change greatest? (ii) Calculate the rate of population change over the period in (c)(i) above. (d) What change in population would be expected if the investigation was continued to the 19th month? (e) To obtain the observed results state two variables that were kept constant during the investigation.
answers
(b) (i) No change in population/population is constant: mice still maturing/have not given birth:
(ii) Slow/gradual population growth; few mice have reached sexual maturity; (iii) Faster/rapid rate of population growth/exponential; Many mice sexually matured/reproducing/enough food/space/no competition birth rate higher than death/no diseases: (iv) Population decline; Competition is high / food is limiting / space is limiting/accumulation of toxic waste/disease (outbreak) deathrate higher than birth rate. (c) (i) 6 and 8; (ii) 310-115 = 195 mice per month; (d) Population would increase; (e) Food; space ; cage size; water;
K.C.S.E Biology Q & A - MODEL 2013PP1QN27
State the importance of moulting to an insect.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN27
State two differences between complete and incomplete metamorphosis.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN19
State three factors in seeds that cause dormancy.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN18
How is the human sperm cell structurally specialised?
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN17
Name the flower part that produces gametes.
answers
K.C.S.E Biology Q & A - MODEL 2013PP1QN16
Name three mechanisms that ensure cross pollination takes place in flowering plants.
answers
Describe how environmental factors increase the rate of transpiration in terrestrial plants.26/6/2020
K.C.S.E Biology Q & A - MODEL 2012PP2QN08
Describe how environmental factors increase the rate of transpiration in terrestrial plants.
ANSWERS
In bright light; stomata are fully/wide open; increasing contact between the atmosphere and air spaces in the leaf; This in turn increases water loss by evaporation through the
open stomata High environmental temperatures; increase the rate of evaporation from the leaf surface thus more water leaves cells due to the increased diffusion gradient; Iii a windy day; air around the leaf is carried away reducing water vapour around the leaf; more water moves into the atmosphere from the leaf air spaces; In low humidity/when the atmosphere is less saturated with water vapour; more water will move from leaf air spaces into the atmosphere; leading to increased rate of transpiration; . Low atmosphere pressure; increases diffusion gradient between atmospheric and leaf increased rate of evaporation;Availability of water; causes turgidity of guard cells hence stomata open; increasing rate of transpiration. |
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