K selection

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selection occurring when a population is at or near the carrying capacity of the environment, which is usually stable: tends to favor individuals that successfully compete for resources and produce few, slowly developing young, and results in a stable population of long-lived individuals.Compare r selection.


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Also K-se·lec·tion [key-si-lek-shuhn]. /ˈkeɪ sɪˌlɛk ʃən/.


K-se·lect·ed [key-si-lek-tid], /ˈkeɪ sɪˌlɛk tɪd/, adjective

Words nearby K selection

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What is K selection?

K selection, or K-selection, is a reproduction process strategy that occurs when a population is at or near the point where the environment can provide for them. K selection favors few but highly efficient births.

In ecology, K stands for carrying capacity, which is the environment’s ability to provide for a particular species. Many factors determine carrying capacity, such as availability of food, amount of space, and number of natural predators. If a species is at or near carrying capacity, there is a lot of competition for food and space and every member of the species must work very hard to survive.

K selection occurs when a species is at or near the carrying capacity. Because the environment is so competitive, babies that are weak or uncompetitive are very unlikely to survive. K selection favors reproduction that results in competitive babies. In practice, this means few, long pregnancies that result in few babies with long maturity periods. While the effort needed to produce these babies is high, the young are much more likely to live long lives and thus are able to reproduce multiple times before dying.

In mammals, large animals, such as  apes, elephants, and whales, tend to be K-selected.

Why is K selection important?

The idea of K selection was formulated by biologists Robert H. MacArthur and Edward O. Wilson in their 1967 book The Theory of Island Biogeography.

In addition to K selection, MacArthur and Wilson also proposed r selection. R selection favors an environment in which a species is nowhere close to carrying capacity. In r selection, an organism produces many offspring and usually plays no part in raising or protecting them. It typically involves the death of a large number of young. Because the environment is uncompetitive, even weak offspring will likely live long enough to reproduce, so little effort can be dedicated to ensuring offspring survival. Insects and spiders are examples of animals that usually rely on r selection.

Often, the terms K selection and K-selected are used comparatively. For example, cats are small mammals whose pregnancies usually last around two months and who can have litters of up to a dozen kittens. Cat maturity usually takes around two years. Are cats K-selected animals? They are when compared to ants but shift toward r-selected when compared to gorillas.

Did you know … ?

Humans tend to be K-selected, with pregnancies lasting a lengthy nine months and sexual maturity taking over a decade to reach. Of course, humans are very complicated animals, and many other factors, such as culture, economics, and geography, also play a role in human survival and reproduction frequency.

What are real-life examples of K selection?

Scientists and biology students use the term K selection to make observations about animal populations.


Quiz yourself!

True or False?

K selection is likely to occur when an environment is highly competitive.

How to use K selection in a sentence