A population is a group of individuals that belong to the same species and confined to a geographic area where they potentially interbreed. The genetic information carried by individuals of a population is known as gene pool. At a geographical location, the population may get well adapted to the environment and are highly homozygous with favorable alleles at high frequency. But the evidences available reveal that the populations exhibit high degree of heterzygosity. The diversity of the population may not be detected phenotypically because genetic diversity is often concealed. The genetic variation can be detected by artificial selection by which the phenotypic characteristics are affected. The variations at the genetic levels are mostly estimated by comparing the nucleotide sequences of the individuals. The amount of genetic variation can be determined by detectable variation at the protein level and at the nucleotide level. Sometimes the nucleotide substitutions result in the silent variations in the gene. Mutation is a sudden heritable change that can occur naturally or it can be induced. The gene shuffling causes inheritable variations during the production of gametes, by the process of crossing over during sexual reproduction. Thus sexual reproduction can produce different phenotypes with various combinations of genes and does not alter the allele frequencies of particular alleles responsible for specific traits. The amount of genetic variation can be determined by detectable variation at the protein level and at the nucleotide level. Sometimes the nucleotide substitutions result in the silent variations in the gene. Studies on various organisms and on different genes resulted in the enormous nucleotide diversity. The extensive genetic variability in most populations exhibited at the DNA level. Almost all genes exhibit the diversity from individual to individual. Especially the alleles represent the variations that are widely distributed among the individuals of the population. Genetic diversity in small populations is reduced because of genetic drift, high degree of inbreeding and reduction in gene flow. These effects are exhibited adversely on a species survival. For example, inbreeding in a population causes the loss of heterzygosity and promotes homozygosity. The recessive alleles received by offspring may be rare and lethal and affect the survival of the offspring. Thus, the low level of genetic diversity in a species extends harmful effects on the survival of the species and populations cannot get rid of \"bad or lethal genes\" due to homozygosity. Solution A population is a group of individuals that belong to the same species and confined to a geographic area where they potentially interbreed. The genetic information carried by individuals of a population is known as gene pool. At a geographical location, the population may get well adapted to the environment and are highly homozygous with favorable alleles at high frequency. But .