Among the five factors that are known to | Class 12 Biology Chapter Evolution, Evolution NCERT Solutions

There are five factors that are responsible for the failure of Hardy- Weinberg equilibrium: gene flow, genetic drift, non-random mating or genetic recombination, natural selection and mutation. This law states that with the random mating, the genes and the genotypic frequencies persist the same generation after generation. There are some assumption that are necessary for this law, population should be panmictic and there would be no natural selection, no mutation, no migration occurs.     

Genetic drift is the random change in the allelic frequency simply as the result of result of chances from one generation to the next in a finite population. Darwin defined the process of natural selection in which the kind of organisms in a population that are best adapted to the environment increases in frequency relative to less adapted forms over a number of generations. Mutation is the source of all genetic variations and is considered as random phenomenon. This randomness of mutation was first demonstrated by Luria and Delbruck in 1943. Gene flow is the transfer of genetic material from one population to another and if its rate is high then two population will have equivalent allele frequencies which is considered as single effective population. And, the exchange of genetic material between different organisms that leads to the production of offspring with the combination of traits is genetic recombination.