r-selected species, unlike K-selected species, are those that emphasize high growth rates, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood. They have traits that maximize reproductive success in uncrowded environments. These species are often found in disturbed environments, or other areas where competition is low. They tend to have short life spans, be small in size, mature early, have many offspring, and they may reproduce only once per lifetime.
In unstable or unpredictable environments, r-selection predominates due to the ability to reproduce rapidly. There is little advantage in adaptations that permit successful competition with other organisms, because the environment is likely to change again.