7. Formation of new Species: As a result of struggle and natural selection, only the individual fits to the environmental conditions will survive and complete its life-cycle. As a result, the number of these individual will increase over the course of time compared to the less favorable organism. In addition, the variation favoring will be inherieted to the next generation whereas unfavorable variation will be discarded. Due to continous selection, a new organism will appear which will be different from their ancesteral form.

Lets see the example of giraffe to understand the Darwin’t theory of natural selection. According to the the theory of natural selection, in the beginning there were two different types of giraffe present on earth; (1) Deer like short height and (2) Long neck and forearms (Figure 8.1). Until the grass was available on land, both of these species were surviving and be able to complete their life cycle. With change in climate and reduction of grass, there might be a struggle for food. The giraffe with long neck and forearms can still be able to eat leaves on the tress but the deer like giraffe could not be able to reach there and died due to starvation. In due course, several round of the natural selection led the giraffe with long neck and forearms dominated the region and be present as new species.