Question

Select the mismatched pairs.
(i) Hugo de Vries - Mutations are sudden, random changes
(ii) Lamarck - Nature selects organisms with favourable variations and this mechanism of evolution is called natural selection
(iii) Ichthyosaurs - Reptiles
(iv) Darwin - Organs develop more if used and will degenerate if disused

• A. (i), (iv)
• B. (ii), (iv)
• C. (iii), (iv)
• D. (ii), (i)

Answer 1

The correct option is B (ii), (iv)

Mechanism of evolution explains the different ways, factors contributing to the process of evolution.

Lamarckism was proposed by Lamarck. His theory was based on the principle that all the physical changes occurring during the lifetime of an individual are inherited to its offspring (theory of inheritance of acquired characters).

Lamarck also proposed the theory of use and disuse of organs which states that if we make more use of a particular organ, it will become stronger and better, while those that are least used will eventually degenerate. He explained this with the help of the development of long necks in giraffes. When a giraffe stretches its neck to eat leaves, a “nervous fluid” would flow in its neck and it enlarges. The organs which the organisms have stopped using would shrink with time.


Hugo de Vries put forward the mutation theory which states that new species are formed from sudden, large and random changes (saltation) called mutations. It forms the basis of evolution. According to him the changes in the genetic structure leads to changes in the phenotype.


He suggested that the sudden remarkable changes in a population are brought about by mutations. This mechanism contradicted Darwin's theory of natural selection. He said that nature will select the organisms with favourable variations (characters that help in survival in that habitat) and they establish. Darwin’s theory of natural selection suggested variations are minor and specific and evolution is a gradual and steady process.


The evolution of the animals began with the evolution of invertebrates around 500 mya. Jawless fishes evolved around 350 mya. Amphibians, which were derived from lobe-finned fishes, later evolved into reptiles. Reptiles of different shapes, sizes, and life patterns flourished during the Mesozoic era many million years ago.

Certain reptiles lived in water at that time like Ichthyosaurs (200 mya), others lived on land. Ichthyosaurs are fish-like reptiles found in marine environments.