K selection

US: (kā′si lek′shən)

WordReference Random House Unabridged Dictionary of American English © 2026

K selection,  [Ecol.]

1. Ecology 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. Cf. r selection. 

Also, K  -se•lec•tion  (kā′si lek′shən).  K -se•lect•ed  (kā′si lek′tid), adj. 

WordReference Random House Unabridged Dictionary of American English © 2026

r selection,  [Ecol.]

1. Ecology selection occurring when a population is far below the carrying capacity of an unstable environment: tends to favor individuals that reproduce early, quickly, and in large numbers so as to make use of ephemeral resources and ensure that at least some offspring survive.

Also, r -se•lec•tion  (är′si lek′shən). Cf. K selection.  r -se•lect•ed  (är′si lek′tid), adj.