The second condition is neutrality of the alleles towards each other such that they are all passed from one generation to another in the same proportion with similar abilities to survive and reproduce in any particular environment. Violation of this condition involves natural selection where one of the alleles adapt better than the other alleles thus possessing the advantages of reproducing and passing its copies to offspring over the other alleles.
The third condition is the effective closure of a population where no individuals leave a particular population or enter a new one. When this condition is violated, the population is opened allowing individuals to move from one population to another hence creating a net flow of genes which results to genetic variations and consequently, to evolution. The fourth condition requires the population to be large enough since it is based on statistics. This is because large populations are less subjected to deviations from the expected sampling. This condition is violated when a certain population is small to allow deviations from the normal frequency of reproducing parental genes.
