Keystone Species (DP IB Biology) : Revision Note

Keystone Species

• Keystone species are species that have a disproportionate effect on the structure and function of their ecosystem

• Their removal can cause significant changes in the ecosystem, including the loss of other species and possible ecosystem collapse

• By protecting keystone species, the stability of the ecosystem can be maintained, which can in turn benefit other species in the ecosystem

• Examples of keystone species include

  • Sea otters, in the kelp forest ecosystem in the Pacific Northwest of the United States, help to control the population of sea urchins; without this control the sea urchins can overgraze vegetation and leave no food or habitats for other species

  • Beavers build their homes in running water, slowing the water flow and creating a wetland habitat which can support many other species

  • Elephants, in the grasslands of Africa, consume shrubs and small trees, maintaining the grassland and preventing the growth of larger plants; this maintains food for grazers such as zebras, in turn maintaining the food supply for large predators such as lions

Photo via Unsplash 

Sea otters are an example of a keystone species