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Species diversity and ecosystem resilience

Review your understanding of species diversity, ecosystem resilience, and the impacts of habitat loss on generalist and specialist species in this free article aligned to AP standards.

Key points

  • Biodiversity describes the enormous variety of life on Earth. An ecosystem's biodiversity includes genetic, species, and habitat diversity. But, because species are the basic units of biological classification, biodiversity is most commonly associated with species diversity.
  • A measurement of species diversity includes two components: species richness and species evenness.
    • Species richness is the number of different species in an area. An ecosystem with more species has a higher species richness.
    • Species evenness describes species' relative abundance in an area. An ecosystem that contains roughly equal numbers of individuals across multiple species has a higher species evenness than an ecosystem that is dominated by a single species.
    • Species diversity increases with both species richness and species evenness.
  • Ecosystem resilience is the ability of an ecosystem to absorb change and return to the same equilibrium state after a temporary disturbance.
  • Ecosystems with higher species diversity tend to be more resilient. If an ecosystem has a diverse community of organisms, they are not all likely to be affected by a disturbance in the same way. So, if one species is nearly killed off, a functionally similar species can take its place, maintaining the function of the ecosystem as a whole.
  • The effect of an ecological disturbance on a species depends on its role in the ecosystem, or its ecological niche. Niches can be used to classify species as either generalists or specialists.
    • Specialist species have narrow niches. They may live only in one type of habitat, use just a few types of food, or tolerate a narrow range of environmental conditions. Specialist species have a competitive advantage in their undisturbed environment, but they are highly sensitive to habitat loss. As a result, many specialist species are becoming threatened, endangered, and extinct due to human activities.
    • Generalist species have broad niches. They can live in different types of habitats, eat a variety of foods, or tolerate a wide variety of environmental conditions. Generalist species are affected by habitat loss, but adapt more quickly than specialists, and are more likely to spread into new environments.
A giant panda with leaves in its mouth and holding a stalk of bamboo.
Giant pandas are a specialist species because they rely exclusively on the bamboo forests of China for habitat and food. Image credit: “Giant Panda Eating" by Chen Wu, CC BY 2.0.

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