How do genetic drift, gene flow, mutation, non- random mating and natural selection cause microevolution?

Hint: Microevolution is generally the changes taking place at the gene (or allelic level) which automatically affects the gene frequencies in a population. There are several ways about how it takes place which are – genetic drift, gene flow, mutation, non-random mating and natural selection.

Complete answer:
Genetic drift- If evolutionary process depends on chance alone it leads to genetic drift. That means change in the amount or proportion of genes from one generation to next and this is totally because of a chance event. For e.g. if a certain population has a particular percentage of ‘A’ allele and a particular percentage of ‘a’ allele in the next generation it may change.

Gene flow- When an individual moves from one place to another either by emigration or by immigration it leads to flow of gene from one gene pool to other. Whether a person moves from one place to another or people may come from one place to another in both cases leads to flow of genes.

Mutation- It means sudden and spontaneous change in DNA. This spontaneous change may lead to microevolution which may have positive or negative effects in a species.

Non-random mating- When a particular species chooses their own mate for mating it leads to non-random mating and contributes to evolutionary change.

Natural selection- This is a very important concept wherein the most suited variety survives and is selected by nature and that’s how evolution takes place. For e.g. if out of green and brown beetles only green beetles are being eaten up more survival of brown beetles gets maximised.

Note: For evolution to take place for the entire community the change must begin from gene level which will further lead to macroevolution to take place. Finally at the end it is always the survival of the fittest i.e. whichever species survives the odd undergoes evolutionary process.