A life-history paradigm has replaced the r/ K selection paradigm, but continues to incorporate its important themes as a subset of life history theory. The theory was popular in the 1970s and 1980s, when it was used as a heuristic device, but lost importance in the early 1990s, when it was criticized by several empirical studies. Wilson in 1967 based on their work on island biogeography although the concept of the evolution of life history strategies has a longer history (see e.g. The terminology of r/ K-selection was coined by the ecologists Robert MacArthur and E. In contrast, more stable environments allow parents to confidently invest in one offspring because they are more likely to survive to adulthood. An unstable environment would encourage the parent to make many offspring, because the likelihood of all (or the majority) of them surviving to adulthood is slim. The stability of the environment can predict if many expendable offspring are made or if fewer offspring of higher quality would lead to higher reproductive success. The concepts of quantity or quality offspring are sometimes referred to as "cheap" or "expensive", a comment on the expendable nature of the offspring and parental commitment made. The focus on either an increased quantity of offspring at the expense of individual parental investment of r-strategists, or on a reduced quantity of offspring with a corresponding increased parental investment of K-strategists, varies widely, seemingly to promote success in particular environments. In ecology, r/ K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. Whale reproduction follows a K-selection strategy, with few offspring, long gestation, long parental care, and a long period until sexual maturity. A North Atlantic right whale with solitary calf.
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