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Evolution

Short Answer Type

71. Describe De Vries Mutation theory.

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72. What is the main difference between Darwin's theory of natural selection and De Vries mutation theory ?

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73. What is competition in nature ? How does it affect the plant and animal life ? Mention some examples.

Competition is defined as struggle for existence between organisms of the same species, variety, genus or family etc. The reason for struggle in production of a large number of individuals by an organism. As the space and food is limited, hence the individuals compete with one another.

As a result of struggle for existence, only the fittest survives while the weak ones die.

Due to change in the environment, an organism which survives, adapts itself to the changed environment. This brings variations in the organism.

The variations are the raw materials of evolution. By the inheritance of some of these variations in successive generations, new species are formed both in plants and animals, e.g. progeny of pea plant.

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