Define r and K Strategists?
Ecologists have identified two major types of reproductive strategies among species. Characteristic patterns can be seen among species relating the type of environment they inhabit to their physical size, numbers of offspring, life span, term of parental care, and level of competition among species and between species.
Species such as plants we call weeds, bacteria and insects, which have fast population growth rates, are usually small and grow to maturity in relatively short periods of time. These are called r strategists because they exhibit high rates of intrinsic natural increasethe J-shaped growth curve. They increase exponentially and then reach a maximum due to a limiting factor, then crash. The K strategists are usually larger, like elephants, whales and giant redwoods. These populations have more stable environments, and reach a carrying capacity.
In other words, unstable environments, which often produce temporary conditions because of normal disturbances, would be considered not well-suited to support a species that have large bodies, that are slow breeding, produce small numbers of offspring that are slow to develop, and require long life-spans. Why not? Well, large bodies require longer periods of growth. A long growth and development period requires a stable food supply, which would probably not be possible in unstable conditions. A small number of offspring means that if conditions interfere with their development and survival, the population suffers immediate losses that are not easily or quickly replaced. Long life spans translate into delayed reproduction cycles, which, if interfered with by an unstable condition, do not add individuals to the population. r-strategist offspring require little if any care, and can survive on their own.
On the other hand, K strategists can be usually found in stable and predictable environments. They depend upon their ability to exploit limited resources by forming complex competition relationships. Their life spans cover long periods of time since their environments tend to be stable. They dont require huge numbers of offspring in order to survive as a population, since most of the offspring will not be subjected to instability.