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