Quiz: Changes in Ecosystems

Some grass species need fire in order for their seeds to germinate. Why might this adaptation be useful for grasses?

• Fire allows trees to grow and to provide shade for the grasses.

• The hot temperature of the fire helps the grasses grow faster.

• Seeds can germinate in an area that has been cleared by a fire.

• Fire discourages grazing by large animals so the grasses can grow higher

The diagram models succession in an ecosystem. How can you tell from the diagram that this is an example of secondary succession rather than of primary succession?

• A. No plants exist when the process begins.

• B. Soil is present at the beginning of the process.

• C. The process ends with the growth of large trees.

• D. The sizes of the plants generally increase over time.

Which statement best describes ecosystems?

• They can never change once they are established.

• They constantly change in different ways over time.

• Ecosystems always revert back to their original state.

• Each ecosystem can exist for only a specific length of time.

Which of these might result from the process of natural eutrophication?

• A pond becomes a meadow.

• A rock breaks down into soil.

• A glacier retreats to expose new land.

• A nonnative species takes resources from native species

The table lists the number and variety of organisms in four different ecosystems. Predict what would happen to Ecosystem 3 immediately after a volcanic eruption.

• A. Its biodiversity would decrease.

• B. Its biodiversity would not change.

• C. The number and variety of organisms in the ecosystem would be greater than those in Ecosystem 1.

• D. The number and variety of organisms in the ecosystem would be greater than those in Ecosystem 2.

How is secondary succession different from primary succession?

• Secondary succession occurs over a longer period of time than primary succession.

• Secondary succession occurs when animals are introduced to an area that had only plants.

• Secondary succession occurs after a disturbance in an area that was previously uninhabited.

• Secondary succession occurs after a disturbance in an area in which the soil has remained intact.

What is the first step in the eutrophication of a pond?

• A. A meadow develops.

• B. Plant communities take over.

• C. Excess nutrients build up in the water.

• D. Debris builds up on the bottom of the pond.

The dam would affect the ecosystem behind and in front of the dam by:

• Increasing water flow and biodiversity in both areas.

• Creating a reservoir behind the dam and reducing water flow in front, impacting habitats.

• Making no significant changes to the ecosystem.

• Improving fish migration upstream.

Predict how a dam might affect the fish that live and breed in that river.

• A dam might block fish migration and disrupt breeding.

• A dam might increase fish population.

• A dam might have no effect on fish.

• A dam might make the river flow faster.

The picture shows an ecosystem that experienced a flood several months before. The ecosystem shown is more likely a result of:

• Primary succession

• Secondary succession