who came up with the idea of classifying organisms as an r-strategy or k-strategy survival?

Answer 1

The terms were first used by Robert MacArthur and E.O. Wison in their book "The Theory of Island Biogeography," published in 1967. The letters 'r' and 'K' are variables in several population growth models, where 'r' is the growth rate of the population and 'K is the carrying capacity of the environment. r-selected organisms tend to be habitat generalists that can colonize numerous environments, they reproduce rapidly, and typically have short lifespans, but they are not very good competitors with other species. K-selected organisms tend to be good competitors within their defined niche and they typically have long lifespans but produce few offspring.

MacArthur and Wilson used islands as models to evaluate theories on population growth because islands have a finite carrying capacity, and organisms that colonize islands generally had to come from nearby mainlands. In their theory on island biogeography, they proposed that the number of species on any island reflects a balance between the rate at which new species colonize it and the rate at which populations of established species become extinct. Species that arrive first on a new island have no competitors, but its up to chance whether the environmental conditions are suitable for a new species to survive. Therefore, early colonists are most likely to r-selected since generalists are capable of surviving in a wide range of environments, while k-selected species are less likely to find environmental conditions necessary for their survival. As time passes, more and more species eventually become introduced to an island, and with each new species, competition for resources is likely to increase, and fewer places are available for colonization. Therefore, as the number of species increases on an island, r-selected organisms begin to decline in number or in population size, while k-selected species tend to increase.