Changing Ecosystems

This image shows a forest that has recently burned as part of a forest fire. You can see that many of the trees and larger plants have been killed. But you can also see that the smaller plants, such as grasses, are beginning to grow again. What do you think will happen over time in this forest ecosystem?

• Trees will no longer be able to grow in this area after it was burned, and no animals will be able to live in this ecosystem again.

• Only new plants will be able to move into the burned area and grow, but the ecosystem will never become a mature forest system again.

• More plants and animals will be able to move into the burned area and grow, but the ecosystem will never become a mature forest ecosystem again.

• More plants and animals will be able to move into the burned area and grow, and the area may turn into a mature forest ecosystem again.

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Amelia is an eighth grader who likes to go exploring in a grassy field near her house. She knows that the field used to be part of a local farm and that the farm was built by cutting down a forest. If no human changes that grassy field and Amelia goes back to visit her old neighborhood when she is 80 years old, what do you think she will see there?

• a young forest

• a grassy field

• a tropical rainforest

• a small river and pond

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After a heavy spring rainstorm, Jesse, notices that there has been some heavy erosion along the creek in his neighborhood. The entire bank of the creek has fallen away, leaving just raw soil. Over the next few months the bank of the creek is not disturbed again. What does Jesse notice during that time?

• Nothing will grow in the raw soil.

• Trees will grow in the bank of the creek.

• The bank of the creek will return to its original state.

• Plants and animals will begin to colonize the bank of the creek.

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The wolf population on Isle Royale, an island in Lake Superior, has died out due to a devastating disease. Remember that wolves on Isle Royale eat almost exclusively moose, and moose are herbivores that graze on small shrubs and grasses. Use the information in the figure below to answer the question.Without wolves on the island, what will happen to the Isle Royale ecosystem?

• Moose populations will increase, causing an increase in plant populations.

• Moose populations will decrease, causing a decrease in plant populations.

• Moose populations will increase, causing a decrease in plant populations.

• Moose populations will stay the same, causing no change to the ecosystem.

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In California most of the rivers that flow from the mountains to the ocean have dams on them. One of the species that is affected by dams is Chinook salmon. They lay their eggs in mountain streams and spend the rest of their time in the ocean. Dams prevent Chinook salmon from getting from the ocean to the mountain streams they need for reproduction. Human communities benefit from water in reservoirs. They also benefit from harvesting Chinook salmon in rivers as they migrate between the ocean and the mountains. Which describes criteria the engineers need to consider before developing a solution for preserving ecosystem health?

• Be low in cost.

• Ensure that water is available in reservoirs for human use.

• Stop Chinook salmon from traveling to mountain streams.

• Ensure that Chinook salmon can travel between the ocean and the mountain streams they need for reproduction.

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You are outside bird watching and come across these pileated woodpeckers caring for their young in a tree hole nest. You then notice another tree with small owls and ducks using the woodpeckers nest holes from last year. Which of the following claims could you make based on your observations?

• Pileated woodpeckers do not change the ecosystems they live in.

• Pileated woodpeckers cannot live in ecosystems without owls, bats, or ducks that use their nest holes.

• In ecosystems without pileated woodpeckers, populations of owls, bats, and some ducks decrease because they have fewer nest holes to raise their young in.

• In ecosystems without pileated woodpeckers, populations of owls, bats, and some ducks decrease because of competition with pileated woodpeckers.

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