Although every organism struggles to survive, individual survival is not enough to ensure continuation of the species. Individuals must reproduce. Scientists have identified two strategies for leaving living descendants. Let's compare these strategies. 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. 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.