Oysters and many other mollusks produce many offspring of which only a few survive to adulthood and then have little risk of predation with their strong adult shells. Oysters are an example of an organism with a type survivorship curve.

Acertain species of fish can have either long or short fins. the allele for long fins is dominant over the allele for short fins. a heterozygous, long-finned fish is crossed with a homozygous, short-finned fish. of the offspring, will have long fins and be , and will have short fins and be .