Ecology CFU 1

One characteristic of a stable ecosystem is

• a high number of predators

• an interdependence of organisms

• a lack of biodiversity

• an increase in human interference

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Which level of the pyramid below is correctly paired with the type of organism that would most likely be found at that level in an ecosystem?

• Level A – producers

• Level B – carnivores

• Level C – herbivores

• Level D – decomposers

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Which statement best describes what is most likely to occur if an animal population grows larger than the carrying capacity of its environment?

• The birth rate will increase.

• Both the birth rate and death rate will decrease.

• The death rate will increase.

• Neither the birth rate nor the death rate will decrease.

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Many biotic factors affect individuals in a population. An example of an organism being directly affected by a biotic factor is

• a squirrel cannot find a mate

• a flood washes away a maple tree

• a plant is in a dark room

• a chipmunk finds a rock pile to use for a home

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Scientists have studied the return of plant life on Mount St. Helens ever since the volcano erupted in 1980. Wildflowers began colonizing the area, followed by shrubs and small trees. Scientists predict that it will likely take hundreds of years before the area returns to a forest dominated by fir and hemlock trees. These changes are an example of

• humans degrading an ecosystem by removing wildflowers

• the loss of genetic variation in a plant species

• the growth of a forest through ecological succession

• the biological evolution of wildflowers, shrubs, and trees

The bar graph below shows the number of species in four pond ecosystems. Based on this information, which ecosystem is likely to be the most stable? 

• A

• B

• C

• D

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The diagram below represents an energy pyramid. Which type of organism could occupy levels B, C, and D of this energy pyramid?

• consumer

• producer

• autotroph

• carnivore

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The graph below represents some changes in the number of individuals in a particular population in a stable ecosystem over a period of time. Which statement best describes the trend shown in this graph?

• Ecosystem conditions will eventually cause a population to become extinct.

• In a stable ecosystem, the number of individuals in a population is usually maintained within a certain range.

• The interactions between a population and various factors in an environment are always predictable.

• In order for any ecosystem to maintain a balance, populations must be reduced to half their original number.

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The hemlock woolly adelgid is an invasive insect species that is destroying native hemlock trees in New York State. These insects can upset natural ecosystems because they

• provide food for native bird species

• can carry diseases that can be spread to pets

• increase biodiversity in New York State forests

• disrupt habitats that native species depend upon

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Which activity would eventually result in a stable ecosystem?

• deforestation in an area to increase space for the species living there

• mowing a large field so it can be used for recreation

• allowing native plants to grow undisturbed in an abandoned field

• spraying pesticides on a field at the end of each growing season

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