How Ecosystems Can Recover Over Time

Which ecological process is illustrated in this sequence of pictures?

• biological evolution

• ecological succession

• nitrification

• precipitation

What factor drives the process of terrestrial succession in which this lake

becomes a forest?

• growth of microorganisms

• increases in insect population

• deposition of sediments

• increases in pH of the water

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Which of the following organisms might first appear in a pond or lake?

• grass

• algae

• small fish

• trees

After a long period of time, a pond or lake will eventually become a stable forest community that is referred to as the-

• pioneer community

• biosphere

• climax community

• moss population

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Biodiversity describes the amount of variation present in an ecosystem. How is the biodiversity of an ecosystem affected as it proceeds through the stages of ecological succession?

• the biodiversity increases throughout

• the biodiversity decreases throughout

• the biodiversity decreases, then increases

• the biodiversity remains steady throughout

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Which sequence best represents the stages of succession that would most likely occur?

• bare rock → forest → moss → lichens

• grassland → forest → marsh → lake

• lake → marsh → grassland → shrubs → forest

• pine forest → grassland → shrubs → lichens

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Ecological succession would best be defined as –

• the natural cycle of carbon being exchanged between producers and consumers

• communities replacing each other until a stable community is formed

• ecosystems being consistently altered by a number of natural disasters

• energy flowing through organisms in complex food webs

During ecological succession, a grass community is replaced by a community of shrubs. This change is primarily a result of the fact that the grass community –

• evolves over several decades into a new species bushes that dominates the ecosystem

• was no longer able to produce viable offspring which could live in this ecosystem

• removed nutrients from the soil until only shrubs were able to grow

• modified its environment making it more suitable for the shrub community

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At the end of ecological succession, a stable community is reached. Which of the following best describes a climax community if it left alone?

• most of the biomass is in lichens

• it does not contain any animals

• it changes very quickly

• it remains until the climate changes

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Which of the following scenarios could explain the

drop in biomass labeled X in the graph to the right?

• Felled trees are replanted by humans

• A forest fire is started by lightning

• Bioaccumulation of toxins affects top predators

• Pollution in an ecosystem is drastically reduced

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