Syllabus Edition

First teaching 2023

First exams 2025

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Keystone Species (SL IB Biology)

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Naomi H

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Naomi H

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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
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Photo via Unsplash 

Sea otters are an example of a keystone species

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Naomi H

Author: Naomi H

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.