Define and explain variation with example.

Variation is defined as the change which can be observed at the phenotypic and the genotypic level. There are different causes of variation like due to natural selection, germinal variation, etc. Germinal variation is the variations among the organism due to genetic difference. Horn is the phenotypic character of the cattle whose expression is based on the expression of the gene related to the horns. If the gene of horn gets suppressed in some cattle, then the cattle become hornless.