Name: Fossils as Evidences of Evolution
Uploaded: 2019-07-19
Duration: 3 min 32 s
Description: Fossil remains have been found in rocks of all ages and are of the simplest organisms found in the oldest rocks, as well as fossils of more complex organisms.

Question

Give the salient features of the theory of Natural Selection proposed by Charles Darwin.

Accepted Answer

The theory of Natural selection proposed by Darwin has the following salient features:

1. Overproduction: All organisms possess enormous fertility. They multiply in a geometric ratio. Thus, some organisms produce more offspring and others produce fewer offspring. This is called differential reproduction.

2. Limited food and space: Despite rapid multiplication of all types of species, food and space and other resources remain limited. They are not liable to increase.

3. Struggle for existence: The struggle for existence can be of three types.

Intraspecific struggle: It is a struggle between the individuals of the same species because their requirements like food, shelter, breeding places, etc. are similar.

Interspecific struggle: It is the struggle between the members of different species. This struggle is normally for food and shelter.

Environmental struggle: It is the struggle between the organisms and the environmental factors, such as drought, heavy rains, extreme heat or cold, earthquakes, diseases, etc. Thus, climate and other natural factors also help in restricting the number of individuals of particular species.

4. Appearance of variations: Due to the variations, some individuals would be better adjusted towards the surroundings than others. Adaptive modifications are caused by the struggle for existence. According to Darwin, the variations are gradual (continuous) and those which are helpful in the adaptations of an organism towards its surroundings would be passed on to the next generation, while the others disappear.

5. Natural Selection or Survival of the Fittest: The organisms which are provided with favourable variations would survive because they are the fittest to face their surroundings, while the unfit are destroyed. Survival of the fittest is not enough. The organisms should also adapt or change themselves according to the changed conditions of the environment as the environment is always changing.

6. Inheritance of useful variations: The organisms after adapting to the surroundings transmit their useful variations to the next generation, while the non-useful variations are eliminated.

7. Speciation: Darwin considered that useful variations are transmitted to the offspring and appear more prominently in succeeding generations. After some generations, these continuous and gradual variations in the possessor would be so distinct that they form a new species.

Give the salient features of the theory of Natural Selection proposed by Charles Darwin.

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