Reproductive Strategies (HL) (DP IB Environmental Systems & Societies (ESS))

Reproductive Strategies

• r-strategist species and K-strategist species have different reproductive strategies that make them suited to different ecological roles:

  • r-strategists thrive in unstable or early-stage ecosystems (like pioneer communities)

  • K-strategists are better suited to stable, long-established ecosystems (like climax communities)

r-strategist species

• r-strategists are species that produce large numbers of offspring quickly

  • They are adapted to maximise reproduction in a short amount of time, especially in environments where resources are temporary or unpredictable

• They invest little energy in the care of each individual offspring, meaning survival rates for each individual are low

• These species are often found in environments recovering from disturbances, such as areas cleared by wildfires or abandoned agricultural land

• r-strategists are particularly successful in pioneer communities, where they can rapidly colonise bare or disturbed ground and take advantage of the sudden availability of resources like nutrients and sunlight

  • In these environments, competition is low, and the conditions are favourable for rapid population growth

K-strategist species

• K-strategists producing fewer offspring but investing more energy into their care (quality over quantity)

• They typically live in stable environments where competition for resources is high, so producing fewer offspring and ensuring their survival is a better strategy

• These species usually have longer life spans and a slower reproductive rate

• K-strategists are particularly successful in climax communities, where ecosystems are fully developed and competition for space, nutrients, and light is intense

• K-strategists are better suited to long-term survival and tend to be found in environments that have reached their carrying capacity, meaning the ecosystem can support only a limited number of individuals

Comparison of r- and K-strategist Species