9/10/25 Food Webs and Ecosystem Interactions Quiz

What was one effect of removing wolves from Yellowstone in the early 1900s?

• The number of elk decreased

• Wetlands expanded

• Elk numbers grew too high

• Beavers built more dams

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Explain how the removal of one predator, such as the wolf, can disrupt the balance of an ecosystem. Use evidence from the passage to support your answer.

• Removing a predator has no effect on other species.

• Removing a predator can cause prey populations to grow too high, which can harm plants and other animals that depend on those plants, disrupting the balance of many species.

• Removing a predator makes all animals safer and increases biodiversity.

• Removing a predator only affects the predator itself.

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What happened to the elk population when wolves returned to the area?

• The elk population increased.

• The elk population decreased.

• The elk population stayed the same.

• The elk population moved to the mountains.

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When wolves returned, the balance began to recover. Elk populations decreased, and they avoided risky river areas where wolves hunted. Willow and aspen trees grew back, beavers returned, and wetlands expanded. Other animals, like ravens and bears, also benefited from the food wolves left behind.

In the end, food webs are fragile systems built on interdependence. Producers provide the base of energy for all consumers. Predator–prey relationships, cooperation, and competition all play roles in survival. Yellowstone shows that removing or adding just one species can ripple through the web and change the whole ecosystem. Scientists study these interactions to understand how ecosystems stay balanced and why protecting biodiversity matters.

Based on the passage, what is the central idea of the two paragraphs?

• Wolves are the most important animals in Yellowstone.

• Food webs are fragile and depend on the balance and interdependence of all species.

• Only predators matter in an ecosystem.

• Wetlands are the best habitats for animals.

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If a Northern harrier eats a Spruce grouse, what type of relationship is this?

• Competition

• Predator-prey

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Which of the following is an example of competition in a food web?

• Spruce grouse eating seeds

• Northern harrier eating spruce grouse

• Owls and hawks both eating mice

• Mice eating plants

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How can you identify competitors in a food web diagram?

• By finding arrows pointing from the same food source to different organisms

• By finding arrows pointing from different food sources to the same organism

• By looking for animals that live in the same area

• By looking for animals that are the same size

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What is a key pattern found in different ecosystems according to the material?

• Each ecosystem has completely different interactions.

• Similar patterns of interactions occur across different ecosystems.

• Only aquatic ecosystems have patterns.

• Patterns only emerge in tropical ecosystems.

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What does the pine vole need to survive?

(a)  

• swallowtail caterpillar
• black bear
• beaver

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What needs the pine vole to survive?

​ ​ (a)  

• gray fox
• silver maple
• bobcat

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