A strong muscle of a wrestler is an acquired character that can be obtained by regular exercise which will not be transmitted to the next generation. Gene pool of a population will consist of a large number of genes which will vary in their frequencies. These frequencies also depend on the proportion of various genotypes in the total population. The small tribal population will have the small gene pool. Hereditary diseases like colourblindness will spread in isolated population due to inbreeding. There is a decline in population as boys marry girls only from their own tribe, this is due to the absence of gene.