Question

1. Define natural selection. 2. What three conditions did Darwin conclude are necessary for natural selection to take place?

Answer 1

1. Natural selection: the theory of natural selection is proposed by Charles Darwin in 1859 in his book "origin of species". Natural selection is the key mechanism of evolution. Natural selection is a complex phenomena involving many factors. For natural selection variation is necessary, and this variation must be heritable and passed on to progeny.

2. Darwin mentioned following factors (conditions) for natural selection:

a) Overproduction:

b) Struggle for existence :

c) Apearance of variation;

d) Survival of the fittest:

e) the advantageous variations are inherited through fittest and accumulation for a period gives rise to a new species.

According to Lewontin (1970) there are the three principles conditions that explains the on” Darwin’s theory

1. Different individuals in a population have phenotypic variation e.g., different morphology, different physiology, and differentbehavior.
2. Different phenotypes have different survival rates  and reproduction rate in different environmental conditions i.e., differential fitness.
3. There is a correlation between parents and their progenis in the contribution of each to next generations i.e., fitness is heritable