Certain side-chain conformations are energetically favourable, these side chain confirmations are called as Rotamers.

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#Id: 9558

#Unit 11. Evolution and Behavior

Orthogenesis - “Straight-line evolution,” held that the variation that arises is directed toward fixed goals.

So that a species evolves in a predetermined direction by some kind of internal drive, without the aid of natural selection.

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#Unit 11. Evolution and Behavior

Mutationist - Theories were advanced by some geneticists who observed that discretely different new phenotypes can arise by a process of mutation.

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#Id: 9560

#Unit 11. Evolution and Behavior

They supposed that such mutant forms constituted new species and thus believed that natural selection was not necessary to account for the origin of species. The last influential mutationist was Richard Goldschmidt

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#Id: 9561

#Unit 11. Evolution and Behavior

Ronald A. Fisher, John B. S. Haldane and Sewall Wright - which showed that mutation and natural selection together cause adaptive evolution.

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#Id: 9562

#Unit 11. Evolution and Behavior

Neutral theory of molecular evolution

Developed by Motoo Kimura, who argued that most of the evolution of DNA sequences occurs by chance (genetic drift) rather than by natural selection. 

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#Id: 9563

#Unit 11. Evolution and Behavior

Theory of recapitulation - Ernst Haeckel

He proposed that the embryonic development of an individual organism (its ontogeny) followed the same path as the evolutionary history of its species (its phylogeny).