mutation theory

                                   Mutation Theory

Hugo de vries, dutch botanist, one of the independent re discoverer of mendelism, put forward this theory in 1901.

Acoording  to him, new species are not  formed by continuous variation but by sudden appearance of variations(mutations).

Hugo de vries  started that mutations are heritable and persist successive generation.

He conducted experiment on oenothera lamarckiana, (evening primrose)  and founded  several aberrant types.

When this plan was self-pollinated and its seeds were allowed to grow, majority of offspring were similar to the parents, but  a few were different.

The different plant were also pollinated and when their seeds were sown, the  majority of the plants were similar to the parents while a few were still more different.[more variety]

He suggested that new types of inherited characteristics may appear  suddenly without any previous indication of their presence in the race.

 Main points of mutation theory

Mutation or discontinuous variation are the raw material of evolution.

Mutation appear all of a sudden and become operational immediately .

Unlike Darwin continuous variation, mutation do not revolve around the mean or normal character of the species.

The same type of mutation can appear in a number of individuals of the species.

All mutation are heritable.

Useful mutation are selected by nature. Lethal mutation are eliminated. However, useless and less harmful ones can persist in the progeny.

 Evidences in favor of   mutation theory

Mutation are the source of all variation and hence fountain head of evolution.

Mutation theory can explain both progressive and retrogressive evolution.

As the ratio of mutations is not the same in all individuals and their parts, mutation theory can explain the occurrence of both changed and unchanged forms.