Question

According to Hugo de Vries, the mechanism of evolution is ____________.
a) Phenotypic variations
b) Multi sep mutations
c) Minor mutations
d) Saltation

Answer 1

Hint: Hugo de Vries (1848—1935), a Dutch botanist, one of Mendelism's independent rediscoveries, voiced his views on the formation of new species in 1901. He also met with some of the objections to Darwin's theory.

Complete Answer:
Hugo de Vries (1901) advanced an evolution theory, called the theory of mutation. The theory says evolution is a jerky process in which new varieties and species are formed by mutations (discontinuous variations) which function as evolutionary raw materials. The salient features of the theory of mutation are:
1. The raw material of evolution is mutations or discontinuous variations.
2. All of a sudden, mutations appear. Instantly they become operational.
3. Unlike the continuing variations or fluctuations in Darwin, mutations do not revolve around the species' mean or normal character.
4. In some individuals of a species, the same type of mutation may appear.
5. They are all inheritable mutations.
6. Mutations show up in every conceivable direction.
7. By nature useful mutations are chosen. It eliminates lethal mutations. Nevertheless, in the progeny can persist useless and less harmful ones.
8. New species are produced by the accumulation of variations.A new species is sometimes brought on from a single mutation.
9. Evolution is a discontinuous, jerky process.Hugo de Vries believed that the mutation is causing evolution rather than the minor heritable variations Darwin mentioned.
Mutations, although Darwin's variations are small and descriptive, are spontaneous and directional. Evolution is gradual according to Darwin, while Hugo de Vries believed that mutation caused the formation of species and hence known as saltation (single-step large mutation).

Hence the correct answer is option ‘d’ i.e “Saltation”.

Note:This theory makes the mutations directly observable. But later it was thought that mutations alone would not be able to bring about evolution. Also essential to evolution was the natural selection and isolation of mutants.