We see that r-selected organisms have many babies, but most of these youngsters never become adults. Frogs are a good example of r-selected organisms. Frogs lay many eggs and leave them in the water to hatch into tadpoles. Some of the eggs get eaten, and many of the little tadpoles are eaten, too, by dragon-fly larvae and fishes and fishing birds. When the tadpoles become frogs, many animals are waiting on shore to eat them: raccoons, foxes, snakes, cats, and many other small predators. If one frog from a hundred eggs lives to be a parent, his/her survival is really outstanding. But frogs go on because they lay so many eggs.

Elephants are examples of K-selected animals. Female elephants have babies about three years apart, and they have only one each time. The whole group looks after the youngsters, and protects them through childhood and adolescence. By reproducing at a rate that holds their numbers close to constant, elephants are able to survive in stable ecosystems. Because they ensure the survival of a good percentage of their young, elephants do not need to produce many elephant babies.