Mastering KCSE Biology with Comprehensive Topical Questions and Answers
K.C.S.E Biology Q & A - MODEL 1997PP1QN18
An experiment was carried out to determine the growth rates of bamboo and a variety of maize plants in two adjacent plots. The average height and average dry weight of plants from the two populations were determined over a period of twenty weeks. The data is as shown in the table below.
(a) Between which two weeks did the greatest increase in weight occur in
(b) Bamboo plants (ii) Maize plants (b) (i) Which of the two types of plants had a higher productivity by the end of the experiment (ii) Give a reason for your answer in (b) (i) above (c) Between weeks 14 and 18, the average height of the maize plants remained constant while average dry weight increased. Explain this observation (d) Suggest how the change in the average dry weight bamboo and maize Plants would have been at week 22 if the experiment was continued. (e) Why was it appropriate for this experiment to use (i) Dry weight instead of fresh weight (ii) Weight and height (f) Describe how the average height and weight of the plants were determined in this experiment. Average height Average dry Weight (g) Give a reason why secondary thickening does not occur in bamboo and maize plants
answers
(a) (i) Bamboo plants
4 and 6 (ii)Maize plants 12 and 14 (b) (i) Bamboo (ii) It had accumulated more weight and therefore greater dry weight (c) Maize plants have reached maturity/maximum height food being manufactured (in green parts); is utilized for growth storage primary in the cob. (d)Increase in weight – bamboo reject both increase/ decrease accept bamboo and maize increase/ decrease. (e) (i) Dry weight instead of fresh weight Fresh weight is dependant on the amount of water present in the plants and this fluctuates depending on environmental factors. (ii) Weight and height Both given a better measure of growth (f) Average height At every 2 weeks measure the height of samples of plants in each plot: Divide the total height by the number of plants in each of plot. Average dry weight Harvest the sample measure of the plants in each plot; dry to constant weight: And divide by the number of plants (g) Being monocots/ lack (Inter) fascicular cambium:
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K.C.S.E Biology Q & A - MODEL 1997PP1QN17
​Figures 1 and 2 below represent reproductive organ of plants and an animal respectively.
​(a) Which letters in figures 1 and 2 represents the organs that produce female gametes?
Figure 1 Figure 2 (b) What is the function of the structure labeled S? (c) Name the structure labeled W (d) Which letters in figures 1 and 2 represents the structures where fertilization takes place (e) Which letter in figure 1 represents the structure where male gametes are produced?
answers
​(a) Figure 1 R:
Figure 2 T: (b) Development of the foetous/zygote/fertilized/ova/egg/embryo (c) Style (d) R;P; (e) X K.C.S.E Biology Q & A - MODEL 1997PP1QN14
The diagram below represents a simplified nitrogen cycle.
​(a) Name the organisms that cause process E and J
(b) Name the process represented by F and H. (c) Name the group of organism represented by G
ANSWERS
(a) E- Denitrifying bacteria; e.g pseudomonas denitrifications
J- Nitrifying bacteria; Nitrobacteria reject nitrosamines (b) H- Death decay/ decomposition; excretion/ Aminonification putrefaction egestion. F- Nitrogen fixation (c) Plants K.C.S.E Biology Q & A - MODEL 1997PP1QN11
​The following below represents a feeding relationship in an ecosystem
​(a) Write down the food chains in which the guinea fowls are secondary consumers
(b) What would be the short term effects on the ecosystem if lions invaded the area? (c) Name the organism through which energy from the sun enters the food web.
ANSWERS
​(a) Grass→ Grasshoppers → Guinea fowls
Grass→ Termites → Guinea fowls (b) Lions would compete with leopards Gazelle numbers would reduce Grass would increase (c) Grass; 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 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
(a) Describe how insect pollinated flowers are adapted to pollination |
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