What factors is the Theory of Natural Selection based on? List them briefly.
What factors is the Theory of Natural Selection based on? List them briefly.
The theory of natural selection is based on the following factors:
- Over Population ( Over production) of off-springs: Living organisms are extremely fertile thus have the potential of rapid increase. The enormous capacity for reproduction, or fertility, is responsible for this quick rise. Therefore, all living things have the ability to reproduce, which contributes to an overpopulation of offspring.
Examples of Overpopulation:
Salmon: A salmon produces 28 billion eggs in a season.
A single maize plant yields hundreds of seeds.
Housefly: A housefly lays about 120 eggs six times every summer.
Elephants: Elephants are slow breeders with a gestation period of 22 months. It produces six young ones between the age of 30 to 90. If this rate is continued for 750 years, 19 millions can be produced.
- Struggle for Existence: The organisms compete with one another for food and space as a result of an excessive rate of multiplication and scarce resources. Darwin noticed three types of struggle in the organisms;
Intraspecific struggle: It is maximum among the individuals of the same species because of the similar requirements and adaptations. Eg, two dogs for a piece of meat. It is passive
Interspecific struggle: It takes place between the different species. Eg, a cat trying to catch a rat and the rat trying to escape. It is active
Environmental struggle: It takes place against the forces of nature among all the respective organisms. Eg, against extreme heat or cold, lightening, etc.
- Variations and Heredity: Individual differences within a population are referred to as variations. These variations may result from fresh genetic mutations or be inherited from the parents. Variations may take the form of distinct physical traits, physiological traits, or behavioral traits. In a particular setting, some variations might be advantageous while others might be neutral or harmful. The process by which traits are passed down from parents to children is known as heredity. Because genetic information is passed down from parents to children, offspring frequently resemble their parents to some extent. Beneficial variations are more likely to be passed down to offspring when individuals with those variations reproduce. Over generations, the inheritance of useful variations allows populations to adapt to their environment by increasing the frequency of traits that improve survival and reproductive success.
- Survival of the fittest (Natural selection): Natural selection occurs due to the differential reproductive success of individuals within a population based on their traits and how well those traits allow them to survive and reproduce. Generation by generation, animals become better adapted to their environments. Those which are better adopted will survive while the ill adopted will be eliminated soon. (The term survival of the fittest was coined by Herbert Spencer which Darwin had termed as natural selection.)
- Speciation (Origin of new species): The succeeding generations adapt to their environments as a result of passing successful and advantageous variations to their generations. Additional adaptation occurs if the environment changes in any way. Therefore, if natural selection is allowed to continue for a long time, the descendants may end up being completely different from their ancestors and resembling a different species. Once more, in order to adapt to changing environments other members may be adopted in a different manner. As a result, one ancestral species may give rise to two or more new species.
