Question

The mutation theory of evolution was proposed by:
a. Darwin
b. Hugo de Vries
c. Lamarck
d. Huxley

Answer 1

Hint: Mutation is the phenomenon which results in alternation of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism. A Dutch botanist, Hugo de Vries put forward his views regarding the formation of new species in 1901.

Complete answer:
According to Hugo de Vries, new species were not formed by continuous variation but arose due to sudden appearance of variations, which he called mutations. He stated that mutations are heritable and persist in successive generations. He stated this on the basis of experiments carried out by him.

He conducted his experiments on Oenothera Lamarckiana (also called as evening Primrose).When primrose was self-pollinated and its seeds were allowed to grow, the majority of the first generation( also called F1 generation) was similar to parents, but few came out to be different. The different ones were again pollinated and the result came out to be surprising. Out of those plants majority were similar to the parent plant but again few came out to be different, and this pattern was observed generation after generation.

From this experiment Hugo de Vries suggested that new types of inherited characters may appear suddenly without any previous indication of their presence in the race. He believed that mutation causes evolution, not the minor inheritable variation which was mentioned by Darwin. He also added that mutations are random and directionless which causes species formation and hence called Saltation. Based on his observations of this experiment, Hugo de Vries put forward a theory of evolution called mutation theory.

Whereas talking about Lamarck, a French naturalist said that evolution of life forms had occurred but driven by use and disuse of organs. After Lamarck, Darwin gave the concept of natural selection. It stated that those who better fit in an environment leave more progeny than others. These therefore will survive more and hence get selected by nature; he called it as Natural selection and implied it as a mechanism of evolution.

Like Darwin, Huxely also studied natural history while travelling on a naval ship. Initially he didn’t accept the concept of evolution but Darwin converted his opinion with his book On the Origin of Species.

Hence, The correct answer is option (B).

Note: The mutation theory gives direct attention to mutations as it states that evolution is a jerky process where new varieties and species are formed by mutations that function as raw material of evolution. But later on it was thought that evolution cannot occur by mutations only, rather natural selection and isolation of mutants were also essential for evolution.