1. Preteach the vocabulary.
Write ecosystem, food web, and species on the board. Ask students what they already know about these concepts from science class, books they have read, or other contexts. Write their ideas on the board. Then explain each concept to students:
- Tell students that an ecosystem is an environment in which living things interact with non-living things and each other. Provide them with an example, such as the ecosystem in a pond, lake, or ocean.
- Explain that food webs exist within an ecosystem. A food web is made up of a group of animals and plants in which animals eat more than one kind of food. Provide students with an example, such as one food web in the Yellowstone National Park ecosystem: elk eat grass, shrubs, and bark; wolves eat elk, moose, deer, and bison. Tell students that ecosystems have many food webs.
- Explain that a species is a group of living things that share common characteristics and are capable of interbreeding to produce fertile offspring. Provide students with examples, such as humans and sharks.
2. Illustrate the concept of a food web.
Help students make connections between these concepts and their surroundings. Make sure they understand that there is an ecosystem outside of the school that includes species and food webs. As a whole class, draw a simple food web of local animals, such as mice, insects, snakes, owls, and any other species that live in your area.
3. Ask students to brainstorm what it might mean to be a keystone species.
First, illustrate a keystone. Draw a simple, rounded archway made of stones on the board. Point to the topmost stone, the keystone, and tell students that the stone is important because it is holding up the arch; if taken away, the arch would fall. Ask: How do you think keystone species got that name? What might happen if one of the species in a food web vanished? Have students brainstorm the possible effects of a keystone species disappearing. Possible responses may include:
- other species might have to leave
- other species might not be able to find food
- other species might have huge numbers because no one is eating them
- other species might die
Have students make a real-world connection by thinking about what would happen if one of the most important species in your area disappeared. Use the food web of local animals as an example.
Extending the Learning
Students may not realize that they are part of an ecosystem too. Have them describe their ecosystem and draw a simple food web that includes them.
Subjects & Disciplines
- Biological and life sciences
- draw a simple food web
- predict and confirm the effects of a keystone species disappearing
- Hands-on learning
National Standards, Principles, and Practices
National Geography Standards
- Standard 8: The characteristics and spatial distribution of ecosystems and biomes on Earth's surface
National Science Education Standards
What You’ll Need
Materials You Provide
The resources are also available at the top of the page.
- Large-group instruction
An ecosystem is home to interconnected species that form food webs. A keystone species is a species that has a major influence on the structure of an ecosystem. Its presence affects many other members of the ecosystem.
Term Part of Speech Definition Encyclopedic Entry ecosystem Noun
community and interactions of living and nonliving things in an area.
Encyclopedic Entry: ecosystem food web Noun
all related food chains in an ecosystem. Also called a food cycle.
Encyclopedic Entry: food web keystone species Noun
a species that has a major influence on the way an ecosystem works.
Encyclopedic Entry: keystone species predator Noun
animal that hunts other animals for food.