It elaborates on the theory of Natural selection for evolutionary transformation, Principles of Darwinism i. Overproduction Living beings have the ability to reproduce more individuals and form their own progeny. They have the capacity to multiply in a geometrical manner. This will increase reproductive potential leading to overproduction.
ii. Struggle for existence Due to over production, a geometric ratio of increase in population occurs. The space to live and food available for the organisms remain the same. This creates an intense competition among the organisms for food and space leading to struggle.
The struggle for existence are of three types: a. Intraspecific struggle: Competition among the individuals of same species. b. Interspecific struggle: Competition between the organisms of different species living together.
c. Environmental struggle: Natural conditions like extreme heat or cold, drought and floods can affect the existence of organisms iii. Variations The occurrence of variation is a characteristic feature of all plants and animals. Small variations are important for evolution.
According to Darwin favourable variations are useful to the organism and unfavourable variations are harmful or useless to the organism. iv. Survival of the fittest or Natural selection During the struggle for existence, the organisms which can overcome the challenging situation, survive and adapt to Flowchart showing the postulates of Darwinism Overproduction Struggle for existence Variations Natural selection Organisms eliminated from the environment Survival of the fittest Inheritance of acquired characters Gradual accumulation of favourable characters Origin of new species Origin and Evolution of Life 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. v. Origin of species According to Darwin, new species originates by the gradual accumulation of favourable variations for a number of generations. .
Variation Sexual reproduction, which involves meiosis helps in recombination of genes during gametic fusion. This leads to differences in the phenotype of the offspring from its parents. These differences are called variation. Variation is the difference found among individuals of the same