Answer: Modern Synthetic Theory of Evolution.
Julian Huxley proposed term ‘modern synthesis’. This theory was based on the work of Dobzansky.
The salient features are as follows.
i. According to the Modern synthetic theory of evolution, population is considered as a unit of evolution because new species are evolved from a population and not from a single individual.
ii. A group of similar individuals interbreeding among themselves, occupying a geographical area is called genetic population or Mendelian population.
iii. The sum total of genes of all individuals of interbreeding population is called gene pool.
iv. Every gene pool has different genes, each having their own specific gene frequencies.
v. The Modern synthetic theory is based on three main concepts, i.e. Genetic variations, Natural selection and Isolation.
a. Genetic variation:
1. It is the change in gene and gene frequencies.
2. It is the raw material for evolution.
3. Genetic variation in populations is caused by — Gene mutations, Gene flow, Genetic recombination, Genetic drift and Chromosomal aberrations.
b. Natural selection:
1. It brings about evolutionary changes by favouring differential reproduction of genes that bring about changes in gene frequency from one generation to another.
2. Natural selection invariably encourages those genes that assure highest degree of adaptive efficiency between population and its environment.
1. Interbreeding does not occur between two isolated groups.
2. Each group may develop a set of new traits that lead to evolutionary changes and towards formation of new species.
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