Changes in Ecosystems

The final and most stable stage of change in an ecosystem---

• climax community

• forest terminus

• cyclic community

One of the first plants to colonize an area that has been harmed, leaving only barren ground---

• lichens

• honeysuckle bushes

• oak trees

Which are the very first organisms to establish themselves after a fire completely destroys a forest?

• Consumers

• Lag species

• Pioneers

• Producers

An examples of ecosystem change caused by humans---

• A beaver builds a dam and blocks a stream, forming a pond. Organisms that rely on fast moving water die out. Over time, populations of pond-loving species increase in the area.

• When a volcano erupts, the surrounding plants are destroyed and leave only bare lava. Pioneer species begin to grow on the lava. Over time, more and more different species reclaim this area.

• Salvinia, a rootless, aquatic fern, floats on a lake surface forming dense mats. Some attaches to a boat. The boater takes his rig to another lake without removing the plant first.

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Which of the following is FALSE statement about ecosystems?

• Ecosystems naturally change when species modify the ecosystem, such as when beaver build dams.

• Ecosystems naturally change when the populations of organisms in the ecosystem change, such as after a new species of bird migrates to an island.

• Ecosystems naturally change in response to a physical disturbance, such as after a forest fire.

• Ecosystems rarely change in nature. Ecosystems only change in response to human disruptions.

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Select the true statement

• All species in an ecosystem are connected to one another.

• All species in an ecosystem are independent of one another.

• An ecosystem that is out of balance can never be returned to balance.

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An example ecosystem change caused by humans ---

• A fire burns down a large area of forest. Only soil remains. The next season, small plants sprout. Over time, new trees reclaim this area.

• A herd of grazing buffalo tramples on tree seedlings and digs up the ground, destroying the young trees. In the bare patches, new plants grow.

• Automobiles and factories burn fossil fuels, releasing carbon dioxide and pollutants into the atmosphere.

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A wide range of organisms in an area is called---

• biodiversity

• unstable

• similarity

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Conditions for a stable ecosystem include all of these EXCEPT---

• source of energy

• producers using energy sources to synthesize organic compounds

• materials cycling between organisms and environment

• only one type of organism in an area

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