3.2: K-selected and r-selected species

Reproductive strategies

• There are patterns related to how species reproduce:

  • K-selected species

  • r-selected species

• Survivorship curves (Types I, II, and III)

K-selected Species

A species with a low intrinsic population growth rate that causes the population to increase slowly until it reaches carrying capacity.

• Large organisms, late reproductive maturity, few offspring, lots of parental care (large mammals and most birds)

• Cannot respond quickly to changes in environmental conditions and avoid extinction

r-Selected Species

A species that has a high intrinsic population growth rate, which often leads to population overshoots and die-offs.

• Small organisms, early reproductive maturity, reproduce often, many offspring, low care

• Mice, small fish, many insects, weedy plants (roaches, dandelions, and rats)

Traits for K- and r- selected species

Examples of K and r species