Giving three reas

Hardy- Weinberg principle; states that allele frequency in a population are stable and is constant from generation to generation. This is called Hardy-Weinberg equilibrium

Three reasons that affect Hardy-Weinberg equilibrium are:

1. Gene flow/ Gene migration: due to migration, new genes or alleles are added to the new population and these are lost from the old population, in turn changing the frequencies.

2. Genetic drift: Any change occurring in frequencies by chance is called genetic drift.

sometimes due to changes in allele frequency in new population, some different species are formed.

3. Mutations: these occur randomly at a very slow rate. the sudden heritable change which is directionless in gene is called Mutation. This alters the genetic make-up of an individual.