Mendelian population is an interbreeding group of organisms that share a common gene pool. Populations consisting of specimens that cross with each other are usually called Mendelian populations. Dobzhonsky has defined Mendelian population as “a reproductive community of sexual and cross fertilizing individuals which share in a common gene pool.”

A population isolate is that group of persons within which individuals choose their partners. Such an isolate is  called a Mendelian population. The population isolate inhabits an island, a mountain valley, a peninsular region, a forested area, or even a large area covering several villages, where the marriage alliance is restricted within that endogamous group.

A biological population has moving and permeable boundaries which are intimately linked with cultural and social factors. Genetic relationships within and between polulation like allele frequencies, consanguinity, mating patterns, gene flow Population Genetics , natural selection, etc. define the evolutionary genetics of populations.

If  the Mendelian population is not changed by natural selection, nor by mutation, nor by migration, and if the population size is large and if individuals are not mating assortatively (that is, random choice of partners), then Mendelian population is said to be in equilibrium. In other words, there is no evolutionary change if

• No mutation
• Random mating
• No biased migration
• No biased selected mortality (selection)
• No biased random mortality (drift)