Based on the environments they live in, and the stability of these environments, two categories of organisms can be found. They are r and K strategists. This categorization describes the growth and reproductive rates of the organisms as well. r strategist is an organism living in unstable environments. Hence, they undergo rapid reproduction to stabilize themselves. Whereas, K strategist is an organism living in stable environments. Therefore, they are high in population and do not need to undergo rapid reproduction.used by ecologists to describe the growth and reproduction strategies of organisms