Another reason phenotypes may not c

Another reason phenotypes may not change when genes vary is canalizetion. Canalization describes developmental processes that limit phenotypic variation. These processes buffer the phenotype against genetic and environmental perturbations. +Canalized traits in tetrapods include four limbs, two eyes, one mouth, and five digits. Genetic variation affects many other things about those traits, but it only rarely affects their number, and when it does, the consequences are disastrous.