4 postulates of neo darwinism
Answers
2) Limited food and space
3) Struggle for existence
4) Variations
5) Natural selection or the Survival of the fittest
6) Inheritance of useful variations
7) Speciation....
Answer:
Darwinism means theories of natural selection and speciation as put forth by Charles Darwin. The five main postulates of his theories are as follows: Overproduction or prodigality. Struggle for existence, Organic variations, Natural selecton, Origin of new species (speciation).
1. Overproduction (Prodigality of nature) : There is a natural tendency to produce more number of progeny in geometric rado for continuing the species. E.g. Salmon fish produces about 28 lakh eggs in a single season. Single pair of elephants would produce 19,000,000 elephants. But the size of given species in a given area remains relatively coristant because of fluctuations that occur seasonaly.
2. Strugge for existence Due to over- production there is struggle for existence between the members of population for limited supply of food or to overcome adverse environmental condidons or tor a space or to escape form enemies, etc.
3. Organic variations : There are differences in morphology. physiology, nutrition, habit, behavioural patterns, etc., among he members of same species or members of dilferent species. These variaions act as raw material for evolution.
4. Natural selection Some organisms possess better variations to get adapted and survive under existing environmental conditions, while some do not have. Better adapted organisms are selected by the nature while those with unfavourable variations perish. The principle by which useful variations are preserved by nature, is called 'Natural Selection'. It is also called Survival to tittest by H. Spencer.
5. Origin of new species (speciation): Favourable variations are transmitted from generation to generation, resulling into better adapted generations. Gradually these adaptations with few new modifications become fixed in the life cycle, forming a new species