Evolutionary Forces Upsetting H-W Equilibrium :

The following forces upsetting the H-W equilibrium from normal position and results in evolutionary process to occur.

1. Mutation :

Mutation is a changes which occurs at genomic level. Various causes may responsible for the modification of gene and this is called mutation. If mutation occurs at gene level called gene mutation or point mutation or if it is occurs in chromosome then called chromosomal mutation or chromosomal abberation. Mutation is a continuous process.

2. Natural Selection :

On the process of ongoing mutation, due to some environmental changes certain mutation favour the particular type of individuals and unfavour the other and in this way the individuals who are developed favourable character have the capacity to sustain in the midst of environmental change and carried out matting to produce more offsprings, therefore we can called as this particular gene favourable for for individuals generation after generation and ultimately selected by nature, hence called the phenomena as ‘Natural Selection’.

3. Non – random matting :

Non – random matting create consequences which upset H-W equilibrium, because most of the population bears the non-random matting and does not follow random matting. Though mate choosing process is selective one. A particular females selects a particular male with favourable character and matting proceed further. In this selective matting process only a particular genotypes will go on increasing and the other will disappear slowly slowly in due course of time.

4. Genetic Drift :

Genetic drift is the changes occurs in gene frequency by chance in small population. It was explain by Sewall Wright in 1931, hence also termed as ‘Sewall Wright Effect’. When the size of population is small some genes may be reduced in frequency or even lost by chance and other frequency may increased by chance. This result in variation in frequency in entire population and ultimately upset the H-W equilibrium.

5. Migration and gene flow :

Though living creatures are not static, they can move from one place to another, as animal migrates and invade to another area and grow then intimates with the native animals of thier own kind, then there will be a result of transferred of genes from one population to another called gene flow due to the process of migration. Consequences of gene flow is increase or decrease of genes in a gene pool. As the gene frequency changes therefore it upset the H-W equilibrium.