K and r Reproductive Strategies. In the equations describing growth of populations of organisms, r represents the slope of the line representing exponential growth. The letter K represents the carrying capacity of a habitat for members of a given sort of organism. The population is still at low values relative to the carrying capacity of the environment and thus is growing exponentially with intrinsic reproductive rate r (when it is not subject to environmental perturbations.), hence the name r-strategist.As the name implies, r-selected species are those that place an emphasis on a high growth rate, and, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood (i.e., high r, low K).