Life on Earth varies from the microscopic single-celled bacteria to the gigantic redwood trees to the enormous blue whales.

Sources: Salmonella bacteria, BBC News, Sequoiadendron giganteum, Wikimedia Commons, Humpback Whale, Wikimedia Commons

Biodiversity is the variety of life on Earth across all of the different levels of biological organization. There are three main types of biodiversity: species diversity, genetic diversity, and ecosystem diversity.

• Species diversity is the number and abundance of species that occupy a location.
• Genetic diversity is the amount of variation in genetic material within a species or within a population.
• Ecosystem diversity is the variation in the ecosystems found in a region or the variation in ecosystems over the whole planet.

Watch the following video to learn more about biodiversity.

Answer the following question.

1. What is a keystone species?

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   A keystone species is a species that has a disproportionately large effect on its environment.

Long-term survival of a species is based on their limited resources. What are some limited resources that organisms may compete for in nature? Click on the question marks below to find out.

Ecosystem biodiversity can tell us a lot about the health of an ecosystem. The greater the variety of species there are in an ecosystem, the healthier the ecosystem.

Compare the two food webs pictured below. Which food web would be found in a healthier ecosystem?

Food Web A would be found in a healthier ecosystem. There is more variety of species in Food Web A than there is in Food Web B. The more links there are in a food web, the more stable the ecosystem is.