Neo-Darwinism (Modern Theory of Origin of Species)

Neo-Darwinism (Modern Theory of Origin of Species)
Neo-Darwinism is a modern theory of evolution. This theory is the combination of mutation theory given by De-Vries and theory of natural selection given by Charles Darwin. This theory consists of three assumptions:-
Mutation
Natural selection
Isolation
Mutation
Mutation is the sudden change expressed by the development of new characters. This sudden change is due to the change in chromosome or genes. Therefore mutation is two types:-
Chromosomal mutation
Gene mutation
Gene mutation
De Vries belived the evolution is series of change and these change are not due to slow variation, but due to sudden changes by mutation. Mutation is the main factor responsible for the changes. He studied a wild prime rose plant (Oenothera lamarckiana). He found the number of chromosome from 14-30 or more. All this difference in chromosome is due to mutation. The varied chromosome number is associated with varied characters;
 Difference in flower size.
 Difference in flower color.
 Difference in leaf size and shape.
 Difference in nature of stem.
 Difference in bud characters.
 Difference in development.
 Difference in ecological growth habitat.
These different plants are called ‘Elementory species’. Such different plants will add new changes after series of mutation and develop into new species.
Natural selection:-
The change occurred due to mutation may be harmful or beneficial. If the change suit the individual to flight in the struggle for existence, which variation/ change is selected by nature known as ‘Natural selection’. Natural selection gives the validity to the changes and stabilizes towards more development and evolution.