We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is r/K Selection Theory?

Michael Anissimov
Updated May 21, 2024
Our promise to you
All The Science is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At All The Science, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

R/K selection theory is a popular ecological theory developed by Robert MacArthur and E. O. Wilson from their 1967 work on island biogeography. The name is based after 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 a few holes 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 quickly reproducing animals whose specialty is to adopt as many niches as possible using simple strategies, and slowly reproducing animals who are strong competitors in crowded niches and invest substantially in their offspring. These are referred to respectively as r-selected and K-selected species, because the former rely more on growth rate while the latter restrict themselves to effectively exploiting the existing carrying capacity of the environment.

The logic of r/K selection theory further argues that r-selected species do best in unpredictable environments, where specialized adaptations are unhelpful, while K-selected species do well in more predictable environments, where large gains can be made through specialization. Characteristics useful for r-selected species include small size, fast reproduction, short generation time, ability to disperse offspring widely, and an economical approach to nervous system or other auxiliary complexity. Characteristics useful for K-selected species are all the opposite. To oversimplify, r/K selection theory may be thought of in terms of "quality vs. 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 like copepods and barnacles, many birds, rodents, and rabbits. K-selected species are less numerous in terms of biomass — excepting humans and our pets and livestock — but possess considerable diversity and complexity. Examples would include elephants, whales, humans, and tigers. Some smaller animals use K-selected strategies, like the Arctic Tern and the Degu (a rodent).

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By anon993515 — On Nov 20, 2015

It's interesting to see this theory applied to politics. "The Evolutionary Psychology Behind Politics" is very eye opening.

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All The Science contributor and brings his expertise in paleontology, physics, biology...
Learn more
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.