What are the differences between r-selected and K-selected species?

R-selected species have high reproductive rates and low survival rates, while K-selected species have low reproductive rates and high survival rates.

R-selected species, also known as opportunistic species, have a short life span and reproduce quickly. They produce many offspring, but invest little in each one, resulting in a low survival rate. They are adapted to unstable environments and are often found in disturbed habitats. Examples of r-selected species include insects, bacteria, and some fish. For more about how these species interact within their ecosystems, see our notes on ecosystem and niche definitions.

K-selected species, also known as equilibrium species, have a longer life span and reproduce slowly. They produce fewer offspring, but invest more in each one, resulting in a higher survival rate. They are adapted to stable environments and are often found in undisturbed habitats. Examples of K-selected species include elephants, whales, and humans. To understand how these species contribute to population dynamics, explore our detailed notes.

The differences between r-selected and K-selected species extend beyond their reproductive strategies. R-selected species tend to have smaller body sizes, shorter life spans, and faster growth rates, while K-selected species tend to have larger body sizes, longer life spans, and slower growth rates. R-selected species also have a higher tolerance for environmental stress and can quickly colonize new habitats, while K-selected species are more sensitive to environmental changes and have a slower rate of colonization. For insights into the importance of these species in biodiversity, see our related notes.

A-Level Biology Tutor Summary: R-selected species reproduce quickly and in large numbers, but have low survival rates and short lifespans, thriving in unstable environments. K-selected species reproduce slowly and in smaller numbers, but have high survival rates and long lifespans, thriving in stable environments. Examples include insects (r-selected) and elephants (K-selected). These species differ in body size, growth rates, and environmental adaptability. For further understanding of how diseases affect these species, see our notes on pathogens and disease.