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1. All the living species seen today on earth arose from an original ancestor withsimple structure, through, gradual evolution over millions of years. Natural

selection is the motive force of this process. Darting presented this theory in the

form of 5 observations and 3 inferences.

2. Observations:i. The reproductive capacity of all organisms far outstrips the requirement for

propagation/multiplication of the species, with the potential for uncontrolled

increase in numbers.

ii. But the population of all organism are seen to be stable, our severalgeneration, expect for slant fluctuation.

iii. Natural resources are limited, compared to the reproductive potential oforganisms.

iv. No two organisms are similar in all respects.v. Individual variation can be transmitted to succeeding generation.

3. Inferences:i. Excessive reproduction leads to struggle for existence in which only a

small minority in able to service.

ii. Those individuals with characteristics best adapted to the environmentsucceeds in the struggle.

iii. In this way characteristics better adapted to the environment increase andthose which are poorly adapted gradually decrease in a species. This is

natural selection, the force which drives evolution.

4. Artificial SelectionSome useful variations are found to appear occasionally in herds of domestic

animals. Such animals are selected, and mated to produce offsprings which

express the particular character in a more pronounced way. Continuing the

process through many generations, the characterisations are accumulated to

produce better varieties by farmers. Many types of garden plants, fishes and

crops have been produced by man in this manner.

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5. Natural Selection:As man artificially selects better domestic animal and plants, so a similar process

is going in nature. Here instead of variations useful to man, what is selected is

characteristics useful for the survival of the spices and there are accumulated and

developed.

6. Sexual Selection:The elaborate plumage of peacock, and the sweet songs of many birds have no

role in survival, sometimes even become a hindrance. Preserve of such

characters seem to go against theory of natural selection. Fact is, there

characters play important role in mating, so they are selected. Among wild

animals, the strongest made eliminate or dominate other males in the fight for

mates, leading to selection of strong and ferocious race of animals.

7. Speciation:Suppose, from a species of animals, one herd in isolated in a desert and another

in the arctic region. It is possible that the animals with long body hair will survive

more in the arctic. Where as in the desert, characters suitable for life in the desertwill be selected. After many generations, it will be found that, from the original

single type, two sub types or varieties have originated. Small differences

accumulate over generations and give rise to big differences. In coerce of time,

they develop into different species.