Theory question 106
Ecological Associations(a) (i) Name two types of competition (ii) State four factors that bring about competition among organisms.
(b) Outline the relationship between competition and succession.
(c) (i) Explain briefly Darwin's Theory of Natural Selection. (ii) List five evidences to support the occurrence of evolution.
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(a)(i) Intraspecific competition (between members of the same species) and interspecific competition (between different species).
(ii) Any four: limited food/nutrients; space; light; water; mates; shelter/breeding sites; oxygen.
(b) During succession new species invade an area and compete with those already there for light, water and nutrients; stronger competitors replace weaker ones, changing the community step by step until a stable climax community is reached; so competition drives the replacement of species in succession.
(c)(i) Organisms produce many more offspring than can survive; so there is a struggle for existence; offspring vary; those with variations that suit the environment survive (survival of the fittest) and reproduce, passing these variations to their young; over many generations this gives rise to new species.
(ii) Any five: fossil records; comparative anatomy (homologous organs); vestigial organs; comparative embryology; geographical distribution; comparative biochemistry/molecular evidence; adaptive radiation; observed changes such as industrial melanism and drug/pesticide resistance.
Struggle, variation, survival of the fittest, inheritance: the four steps of natural selection.