R/K selection theory categorizes species as r-selected or K-selected based on their reproductive strategies and adaptations to their environment. R-selected species reproduce rapidly and adapt to unpredictable environments, while K-selected species reproduce slowly and specialize in predictable environments. Examples of r-selected species include bacteria, insects, and rodents, while examples of K-selected species include elephants, whales, and humans. Despite some criticisms, the theory is still widely used by biologists and zoologists.
R/K selection theory is a popular ecological theory developed by Robert MacArthur and EO Wilson from their 1967 work on the biogeography of islands. The name is based on variables in an equation used by MacArthur and Wilson that relates the growth rate of various organisms to the carrying capacity of the environment. Although the theory was introduced in 1967, it didn’t catch on until the 1970s. Although some scientists have pointed out some flaws in the theory, it is still used casually and widely by biologists and zoologists.
The key idea of r/K selection theory is that evolutionary pressures tend to drive animals in one of two directions: towards rapidly reproducing animals whose specialty is to adopt as many niches as possible using simple strategies, and animals that reproduce slowly and that are strong competitors in crowded niches and invest substantially in their offspring. These are referred to as r-selected and K-selected species respectively, because the former rely more on growth rate while the latter merely effectively exploit the existing carrying capacity of the environment.
The logic of r/K selection theory further argues that r-selected species do better in unpredictable environments, where specialized adaptations are not helpful, while K-selected species do well in more predictable environments, where large gains can be made through the specialization. Features useful for r-selected species include small size, rapid reproduction, short generation time, ability to widely disperse offspring, and an inexpensive approach to nervous system or other ancillary complexities. The useful characteristics for K-selected species are all opposite. To oversimplify, r/K selection theory can be thought of in terms of “quality versus quantity.”
Species that qualify as r-selected are naturally the most numerous and include the vast majority of all life: bacteria, diatoms and other planktonic animals, most insects and smaller arthropods, crustaceans such as copepods and barnacles, many birds , rodents and rabbits. K-selected species are least numerous in terms of biomass, with the exception of humans, our pets and livestock, but possess considerable diversity and complexity. Examples include elephants, whales, humans and tigers. Some smaller animals use strategies selected by K, such as the Arctic Tern and the Degu (a rodent).
Protect your devices with Threat Protection by NordVPN
