Question

How can you say that variation is an invariable rule in nature?

Answer 1

Hint: The differences in the genetic makeup or phenotype of various organisms are called variations. They occur due to mutations, recombination at the time of gamete formation or due to environmental factors.

Complete answer:
As discussed above, variations are the differences that occur in genetic makeup or phenotypes of organisms. Variations can be of two types-
1. Phenotypic variations- caused due to climate change or conscious efforts. These variations are not inherited and are acquired during the lifetime. They do not play any significant role in evolution.
2. Genotypic variations- caused due to changes in chromosomes or genes. Mutations and recombination result in genotypic variations. They are inheritable and play a major role in evolution.
According to Darwin, no two organisms of any species are alike. There were changes in characters among the offspring of the same parents. They show variations in size, color, health, strength etc. This is because genotypic variations occur during recombination and gamete formation. Organisms also acquire phenotypic variations during their lifetimes. There are much more variations among the members of a population. Thus, variation is an invariable rule in nature.

Note:
Natural selection takes place in four different ways-
Variation- changes occur in organisms over a time period and result in a new species.
Inheritance- variations are passed on over generations which ultimately lead to speciation.
High population growth rate- when a species produces more number of organisms than the environment can support, natural selection takes place and weaker organisms are removed.
Differential survival and reproduction- superior variation causes the survival of particular organisms and the inferior ones become extinct.