What are the key concepts in the evoluti | Class 12 Biology Chapter Evolution, Evolution NCERT Solutions

Charles Robert Darwin provide evidences for the scientific theory that all species have evolved over time from one or few common ancestors by the process of natural selection and this forms the basis of modern evolutionary theory. He publicized a book ‘The Origin of Species’ in which he presented the idea of the natural selection is the mechanism of evolution. Mainly Darwin theory had a combination of five theories: Evolution, Common descent, Multiplication of species (this explains the organic diversity in which species multiply by splitting into daughter species or by budding), Gradualism (evolutionary changes take place gradually not sudden which presents new type of organisms), Natural selection. Mainly there are two key concepts in evolutionary theory of Darwin:

Phylogenetic tree and natural selection:

Phylogenetic tree: it is the most convenient way of presenting evolutionary relationship among the group of organisms through illustrations called phylogenetic trees. It is a two dimensional graph shows evolutionary relationship between organisms and shows by branches and nodes. The branching pattern of the trees is known as tree topology. This contains internal node
(represents last common ancestor of two lineages) and external nodes (represents tip of the trees).

Natural selection: the process by which organisms with favourable conditions or variation will survive and reproduces at higher rate. An inherited variations which increases the chances of organism’s survival in the particular environment is known as adaptation and who will not adapt the variations among the environment will die. Darwin describe the survival of the fittest. Fitness is describe as the ability to survive and reproduce or outcome of the struggle in a specific manner. In the changing environmental conditions which could have the ability to adapt, have the better chances of survival and reproduction.