Polymorphism is the variation within a population. Polymorphism is the occurrence of one or more distinct individual with characteristic difference in phenotype within the members of same species.
Polymorphisms occurs due to genetic variation (which may be a result of mutation or random mating) or due to environmental factors (Geographical distribution)
Polymorphisms can be detected with Morphological markers (different morphological parameters), DNA markers (RFLP, AFLP, SSR, SNP etc.), biochemical markers (Isozymes).