R and K selection

R-selected species are those that place an emphasis on a high growth rate, and, typically exploit less-crowded ecological niches.  They produce many offspring, each of which has a relatively low probability of surviving to adulthood.  In unstable or unpredictable environments, R-selection predominates as the ability to reproduce quickly is crucial.  Among the traits that are thought to characterize R-selection are small body size, early maturity onset, short generation time, and the ability to disperse offspring widely.  R-selected species produce thousands of offspring but provide little to no parental care after birth.  By contrast, K-selected species display traits associated with living at densities close to carrying capacity.  Typically they are strong competitors in crowded niches that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood.  Populations of K-selected organisms are very constant in number and close to the maximum that the environment can bear, unlike r-selected populations, where population size changes more rapidly.  Traits that are thought to be characteristic of K-selection include large body size, long life expectancy, and the production of fewer offspring, which often require extensive parental care until they mature.