K.C.S.E Biology Q & A - MODEL 1998PP1QN15

K.C.S.E Biology Q & A - MODEL 1998PP1QN15

The herbivorous mammalian species were introduced into an ecosystem at the same time and in equal numbers. The graph below represents their populations during the first seven years. Study the graph and answer the questions that follow..

(a) (i) Which species has a better competitive ability?
(ii) Give reason for your answer
(b) Account for the shape of the curve species A between
(i) One year and three years
(ii) Three years and seven years
(c) A natural predator for species A was introduced into the ecosystem.
With a reason state how the population of each species would be affected.

answers

(a)  (i) Species A;
(ii) The rate of multiplication/ growth in A is faster than  of species B
(b)  (i) One year and three years 1-3 years shortage of resources more suitable environmental
Conditions/ such as food space e.t.c resource were not limiting hence the population increased exponentially rapidly; acc correctly named resource e.g food space.
(iii) Three years and seven years 3-7 years shortage of resources/ limiting/ birth rate equals death rate; hence the population had become stagnant/ constant; acc; Environmental resistance has set in rej. Incorrect resources e.g PT and T.
(c) Species A would decrease (because of there is less competition with species A/ More resources available.