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What Are Keystone Species? - Definition & Examples

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  • 0:00 Definition of a…
  • 1:48 Examples of Keystone Species
  • 3:35 Lesson Summary
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Lesson Transcript
Instructor: Linda Fye
Understand the definition and importance of a keystone species in an ecosystem. Read about some examples of keystone species that show how necessary they are for a healthy environment.

Definition of a Keystone Species

Before the 1800s, as many as 60 million American bison roamed the Great Plains. As European settlers arrived, bison were increasingly slaughtered until their numbers reached the thousands. The loss of the bison was devastating to the Great Plains ecosystem. Bison would graze as they migrated and ate only certain types of grasses. They would also trample and roll around in the dirt creating holes that could hold water. Both of these behaviors made the Great Plains very diverse in both plant and animal species, and this kept the ecosystem healthy. The bison's important role in keeping the Great Plains healthy makes them what is known as a keystone species. Fortunately, the bison population has recovered quite a bit, so they can continue their role as a keystone species in some places.

A keystone species is a species that plays a particularly important role in an ecosystem. In order to understand that role, you need to understand what an ecosystem is. An ecosystem is all organisms living in a certain area and the environment surrounding that area. As an example, consider your neighborhood. You, all the other people that live there, the birds and bugs, and all of the plants interacting together would be like an ecosystem. In an ecosystem, a keystone species' importance is out of proportion to the number of species. It was once thought that only the top predators in an ecosystem could be keystone species. A top predator would be like a bear in a forest ecosystem or a lion in an African grassland ecosystem. It is now known that all different types of species can be considered keystone. Anything from plants to microorganisms can have the important role of keystone species in different ecosystems.

Examples of Keystone Species

One example of a keystone species is the prairie dog. They dig tunnels that form prairie dog towns, which can be hundreds of acres in size. The towns help the prairie by providing homes for animals like black-footed ferrets, burrowing owls, and snakes. These animals become food sources for coyotes, birds, and badgers. Also, as the prairie dogs dig tunnels, it churns the soil making it healthier and better for plant growth and insect habitat. The prairie dogs allow better diversity in the prairie, and the prairie would change or die without them.

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