Tag: the paths traversed by life

Mutations are sudden changes in the characteristics of organisms due to chemical changes in the genetic material. The theory of mutation was proposed by Hugo De Vries. Charles Darwin gave the theory of natural selection and Neo-Darwinism is an advanced version of darwins theory.

The term mutation was introduced by Hugo de Vries, while working on evening primrose. He observed aberrent types in $F _1$ generation of two pure breeding varieties. The sudden appearance of new characters was termed as mutation, which he defined as sudden, discontinuous, inheritable changes in genetic material. 

The concept of sudden genetic change, which breeds true in an organism is visualized as a mutation. Any sudden or spontaneous change in character which is inheritable is known as mutation. It is defined as the changing of the structure of a gene, resulting in a variant form which may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes.

Hugo de Vries studied inheritance of flower colour in Oenothera lamarckiana (evening primrose) and proposed mutation theory that says that mutations are sudden, random, and inheritable and discontinuous variations which serve as raw material for evolution. 

a) Theory of evolution was given by De Vries in 1901 which states that evolution is a process where new species are formed due to mutations that functions as a raw material for evolution.

Example for harmful effect of mutation: Oncogenes are harmful mutations can cause cells to become malignant and can ultimately lead to cancer. Mutations are mostly harmful and sometimes neutral (silent mutations)

According to Dobzhansky, mutations, which help organisms in its survival, in the changing environment are accumulated in its genetic composition by natural selection. Mutations are now considered as the ultimate source of organic evolution. By mutations, some old genes can be replaced by new genes in a population to develop changes and thus, mutations play important part in the process of organic evolution.
Thus, the correct answer is option (D), 'Mutation'.

Hugo de Vries gave mutation theory and felt the importance of chance events i.e., mutations during evolution. This was against Darwinian view of evolution as a slow directional process. Mutations are random chance events and result in sudden evolution of characters in a single or few generations.

Mutations are the raw materials of evolution. 

It is sudden heritable change in germplasm.

According to Devries the evolution is very fast like horse running

movement, but not slowly like snails movement as said by Darwin.

Devries also said that there are no middle forms between the ancestor

and new species.