R-selected and K-selected species are terms that biologist use to describe the reproductive strategy of animals. Either an animal produces a large number of offspring and it basically is a numbers game for those offspring or the animals have few offspring and invest a large amount of time in those offspring. R-selected species are those that favor a large number of offspring. This includes animals like insects, amphibians, many fish, and reptiles. They tend to be smaller organisms so the energy used to make each individual is low and live in environments that are unstable. They also have shorter lifespans and reach sexual maturity quickly. They have type III survivorship pattern which means that earlier in life more organisms will die than later on in their life. In these species, the number of offspring is important because it directly impacts the population size.