Question

What are the various causes of variation?

Answer 1

Hint: Variations are modifications seen in organisms. Variation causes every individual to retain their identity through their characteristic features. The genes are the makeup artists for appearances of organisms. Any alteration to the genetic makeup causes one to look different.

Complete answer: Genetic variation is defined as the genetic makeup of organisms within a population change. The alleles or the various versions of a particular gene are inherited from parents to off-springs giving them their characteristic features. Darwin explained the theory of Natural selection in which the survival of fittest is stated. Genetic variation is a necessary component of natural selection, the environmentally selected genes pass on to future generations altering their traits to fit best to the environment. Genes are susceptible to variations or mutations due to many environmental factors. Let us study each factor affecting genetic variation in brief.
a) DNA mutation - Mutations refers to a change in the sequence of genes by some chemical or physical factors. The mutation causes genetic alteration by changing the gene sequence of individuals in a population. Mutation can be a single site or multiple sites. By single site, we mean change in a single base pair of the gene sequence. Multiple site mutation includes alteration in gene frames or changes in more than one nucleotide or base pair in the gene sequence. Moreover, alteration in nucleotides can take place by base addition, subtraction, and substitution.
b) Gene flow - Species reproduce continuously to maintain the number of populations. With every consecutive generation, genes that come from parents combine in different combinations with time. These combinations transfer into the population in new individuals causing genetic variation.
c) Sexual reproduction - This type of reproduction includes variable gene combinations. These variable combinations in a population lead to genetic variation. For example in humans during reproduction gametes from female and male parents combine to form a zygote. During cell division in a zygote, the combination of two gametes undergoes various minor alterations due to recombination causing the zygote to appear different from its parents.

Note: Despite genetic variation is an important process of natural selection it happens due to chance. But natural selection does not happen by chance. It is the result of interactions between the environment and the genetic variations in a population. It should be noticed that it is the environment that decides which genetic variations are better suited for the survival of organisms.