(a)
▪ There has been gradual evolution of life forms with new forms arising at different periods of history.
▪ Any population has built-in variations in characteristics which adapt it better to environment.
▪ The characteristics which enable some populations or individuals to survive better in natural conditions (climate, food, physical factors) would out-breed others (Survival of the fittest).
▪ Those populations which are better fit (reproductively fit) in an environment will be selected by nature and will survive more (Natural selection).
▪ Adaptability is inherited and fitness is the end result of ability to adapt and get selected by nature.
(b) Natural selection is based on following factual observations:
• Limited natural resources.
• Stable population size except seasonal fluctuation.
• Varying characteristics of members of a population.
• Most of the variations are inherited.
