Write a short note on Neo-Darwinism.

Explanation

Modern synthetic theory of Evolution or Neo-Darwinism : Weismann.s germplasm theory, de Vries. mutation theory and Mendel.s laws of inheritance helped a lot in understanding the origin and inheritance of variations. The scientists such as Huxley, Haeckel, Simpson, etc., supported Darwinism. Later Fisher, Sewall Wright, Mayr explained Natural Selection in the light of post-Darwinian discoveries (Synthetic theory/ Genetical theory/ Neo Darwinism). According to this theory, five basic factors are involved in the process of organic evolution. They are (i) Gene mutations, (ii) Chromosomal mutations (iii) Genetic recombinations, (iv) Natural Selection and (v) Reproductive isolation.
(i) Gene mutations : Changes in the structure of a gene (DNA molecule) are called gene mutations or point mutations . They alter the phenotypic characters of the individuals. Thus, gene mutations tend to produce .variations. in the offspring.
(ii) Chromosomal mutations : Changes in the structure of chromosomes (due to deletion, addition, duplication, inversion or translocation) are called chromosomal mutations. They also bring about variations in the phenotype of organisms which lead to the occurrence of variations in the offspring.
(iii) Genetic recombinations : Recombinations of genes due to crossing over during meiosis are also responsible for bringing about genetic variability among the individuals of the same species, thus, contributing to the occurrence of heritable variations.
(iv) Natural Selection : Natural selection does not produce any genetic changes but once genetic changes occurred , it favours some genetic changes while rejecting others. Hence it is considered the driving force of evolution.
(v) Reproductive isolation : The absence of gene exchange between populations is called the reproductive isolation. It plays a great role in giving rise to new species and preserving the species integrity.