Changes in Ecosystems

Some islands are formed by volcanic eruptions, and the islands provide habitats for many organisms.

What is another way volcanic eruptions can benefit an ecosystem?

• blocking sunlight with ash clouds

• transporting seeds

• providing fertile soil

• maintaining a warm ocean temperature

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The trees in a rainforest start to die. This would affect the animals and other plants of the rainforest because it would increase

• rainfall.

• flooding.

• shelter.

• food.

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A large tree was blown over in a forest during a storm. The data table shows the number of plants and plant species in the immediate area before and after the large tree fell.

Which of the following explains why the population changed after this disruption?

• The large tree covered up the soil after it fell and made the area unusable by other plants.

• The impact of the large tree when it fell caused many of the smaller plants below it to die.

• The gap created when the large tree fell allowed sunlight to reach the previously shaded forest floor.

• The large tree released many of its seeds when it fell and those seedlings replaced the tree.

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A variety of small animals and insects can live in a mountain tundra ecosystem. The ground in such places is often rocky with very little soil. The plants that grow there are fragile and grow slowly.

What would most likely happen in the ecosystem if many people carelessly trampled the tundra and killed off the plants?

• The new plants would grow more quickly.

• The populations of many animal species would decrease.

• The amount of soil in the tundra would increase.

• The number of rocks in the tundra would increase.

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During a hot summer drought, an area receives very little rain. The animals that live in the area will probably

• decrease in number and become extinct.

• increase in number, but return to normal after the drought.

• increase in number, and then become extinct.

• decrease in number, and may migrate to another location

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Ice ages can cause the extinction of animals because of a lack of

• oxygen.

• glaciers.

• precipitation.

• food.

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In a particular ecosystem, the climate undergoes a gradual change, resulting in increased rainfall. Mosquitoes living in the ecosystem depend on water for reproduction.

How will this climatic change most likely affect the mosquitoes in this ecosystem?

• It will not affect the survival of the mosquitoes in any way.

• It will force the mosquitoes to migrate to other ecosystems.

• It will lead to an increase in the mosquito population.

• It will lead to a decrease in the mosquito population.

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When a tornado approaches, some organisms flee, and some organisms take shelter; but some organisms are unable to do either.

Which of the following organisms would be at the most risk if a tornado passed through its habitat?

• a red-tailed hawk

• a sparrow

• a groundhog

• a tree

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The diagram shows the temperature range of two fish species in Lake Superior.

What will happen to the species in this ecosystem if the water temperature increases close to the warmest temperature shown on the diagram?

• Both species will survive.

• Species B will survive and species A will die out.

• Neither species will survive.

• Species A will survive and species B will die out.

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What are two ways that a flood can negatively impact an ecosystem?

• spreading pollutants over a large area and restricting animal movement

• increasing groundwater levels and restricting animal movement

• spreading pollutants over a large area and depositing sediment

• increasing groundwater levels and depositing sediment

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