Theory of mutation (de Vries Theory )
A Dutch botanist Hugo de Vries (1848 – 1935) while working on evening primrose (Oenothera lamackiana) observed that suddenly some plants develop different characters. These variation get inherited into the next generation and result in the formation of new species.
He introduced the term mutation for these suddenly appearing variations. He postulated mutation theory which was published in his two volume publication (1900- 1903). He explained that these mutations are responsible for evolution, specially the origin of species. The variations in the members of a species is because of these constantly occurring mutations.
The mutation theory of de Vries can be explained as follows-
- The natural breeding species suddenly develop changes which are called as mutation.
- Mutation are heritable and form new species
- The members with the symptoms of mutation are called as mutant.
- All the species have tendency of mutations that can be less or more.
- The mutations may be useful or harmful.
- The mutations are influenced by natural reelection. The useful mutations survive whereas the harmful are rejected by natural reelection
- The new species are not formed by slow natural selection but it occurs sudden.
- Mutations in the evening primrose is a chance and they can’t be in other organisms .
- The variations in the evening primrose seen by de Vries were not due to mutations but they were because of irregular isolation and conjugation.
- This theory failed to explain isolation and discontinuity among organism.
- It is unable to explain evolution through connecting links.
- Mutation is not the basis of evolution