Question

Define:
(i) Vestigeal organs (ii) Variations (iii) Neo-Darwinism

Answer 1

(i) Organs which are non-functional in the possessor but were functional in their ancestors and in related animals. It is an evidence of organic evolution. For example, nictitating membrane of human eye, vermiform appendix.
(ii) Any difference between cells, individual organism or group of organisms of any species caused either by genetic differences or by the effect of environmental factors is known as variation. Genetic drift, mutation, recombination, gene flow, migration, selection are some sources of variation.
(iii) According to Neo-Darwinism, adaptations are caused due to many forces, natural selection being one of them and that characters are not inherited as such but there are character determines which control their development. It explain the reason for variation.