Natural selection is a driving force for evolution-How ?

Explanation

Darwin published his observation under the name ..origin of species... It elaborates on the theory of natural selectron for evolutionary transformation. The principles of Darwinism tells that nature selectrion is a driving force for evolution.
1. Overproduction : Living beings have the ability to reproduce and have the capacity to multiply in a goemetrical manner.
2. Struggle for existence : Due to overproduction a geometric ratio of increase in population occurs . The space to live and food available for organisms remain the same. This creastes a competition among the organisms, for food and space, leading to struggle.
(a) The competition may be among the individuals of the same species (Intraspecific struggle)
(b) Competition between the organisms of different species living together (Interspecific struggle).
(c ) Natural conditions like extreme heat or cold droght and floods can affect the existence of organisms (Environmental struggle).
3. Variations :
Small variations are important for evolution. According to Darwin, Favourable variations are useful to the organisms and unfavourable variations are harmful or useless to the organisms.
4. Survival of the fittest or Natural selection :
During the struggle for existence, the organisms which can overcome the challenging situation, survive and adapt to the surrounding environment. Organisms, which are unable to face the challenges, are unfit to survive and disappear. The process of selection of organisms with favourable variation is called as Natural selection.
5. Origin of species :
According to Darwin, new species originates by the gradual accumulation of favourable variations for number of generations.