The Hardy- Weinberg theorem of population:

The Hardy- Weinberg theorem:

In 1908, English mathematician Godfrey H. Hardy and German physician Wilhelm Weinberg independently derived a mathematical model describing what happens to the relative frequency of alleles in a sexually reproducing population over time. Their combined ideas became known as the Hardy-Weinberg Theorem. It states that the mixing of alleles at meiosis and their subsequent recombination do not alter the relative frequencies of the alleles in future generations, if certain assumptions  are met. Stated another way, if certain assumptions are  met, evolution will not occur because the relative allelic frequencies will not change from generation to generation, even though the specific mixes of alleles in individuals may vary.

The assumptions of he Theorem are:

1-      Population size must be large. Large size ensures that gene frequency will not change by chance alone.

2-      Individuals cannot migrate into or out of the population. Migration may introduce new alleles into the gene pool or add or delete copies of existing alleles.

3-      Mutations must not occur. If they do, mutational equilibrium must exist. Mutational equilibrium exists when mutation from the wild type allel to a mutant forn is balanced by the mutation from the mutant form back to the wild type. In either case, no new genes are introduced into the population from the sources.

4-      Sexual reproduction within the population must be random. Every individuals must have and equal chance of mating with any other individuals in the population. If this condition is not fulfilled then some individuals are more likely too reproduced than others, and natural selection may occur.

These assumptions must be met if allelic frequencies are not changing that is if evolution is not occurring. Clearly, these assumptions are restrictive and few, if any real population meet them. This mean that most population are evolving.The Hard-Weinberg Theorem does provide a useful theoretical frame work for examining changes in allelic frequencies in population.