Dynamic Nature of Ecosystems

Koalas live almost entirely on leaves from eucalyptus trees, and they are native exclusively to Australia. What will happen if the koalas’ habitat is destroyed?

Answer explanation

Destruction of the koalas’ habitat will most likely lead to the reduction of the koala population.

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An illustration of a water lily is provided. If annual rainfall increased and caused ponds in this ecosystem to become deeper, how might the traits of these water lilies change after many generations?

Answer explanation

The populations of lilies would change to have longer stems.

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The resurrection fern (Selaginella lepidophylla) can shrivel up into a ball and remain that way for many years. When moisture is available, the dry leaves absorb the water and unroll. The plant will then turn green and grow. Under which environmental conditions did this ability develop?

Answer explanation

dry climate, including periods of prolonged drought

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How are ecosystems dynamic in nature?

Answer explanation

Ecosystems are not rigid; rather, their characteristics can vary over time. For example, animal and plant populations may change in number or even decrease completely.

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What is a disruption to an ecosystem that can lead to shifts in its populations?

Answer explanation

A natural hazard such as a forest fire or a flood could lead to shifts in an ecosystem’s populations.

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How could the introduction of a non-native species impact an ecosystem?

Answer explanation

Non-native species can throw off the balance of an ecosystem. Once a species is invasive, it steals the nutrients that native species require in order to survive.

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If a sudden outbreak of disease severely reduced the number of coyotes in an ecosystem very rapidly, what might the resulting changes to the local food web look like?

Answer explanation

Natural prey of the coyote will increase, while any predators of the coyote would search for a new food source or move away.

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Algal blooms happen when too many chemicals containing nitrogen are washed into freshwater areas. What are the effects of significant algal blooms on ecosystems?

Answer explanation

The algal blooms can harm both plant and animal life and make water unsafe for drinking or fishing.

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The peppered moth (Biston betularia) has two forms, a white-bodied and a dark-bodied form. The table provided shows the percentage of each type in a moth population over several years. The data provided on the shift in population of the peppered moth could support a claim that this population is responding to a change in the environment. In order for this data to support that claim, what other data would be needed?

• Data showing that eventually there were no more dark-bodied moths after 1985.

• Data showing that, in 1965, the two forms migrated from different habitats.

• Data showing a steady change in the color of trees in this habitat between 1965 and 1985

• Data showing that in the years after 1985 the trend reversed leading to more dark moths.

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 ​​Information on brown tree snakes is provided along with information on the island of Guam. Brown tree snakes were first brought to Guam in 1950. Which of the following would provide evidence that the change to this environment brought about by the introduction of the brown tree snake has had an effect on the populations of organisms that lived on Guam?

• The population of lizards on Guam in 1960 was very small.

• The longest brown tree snake ever found on Guam measured three meters in length.

• Any of the military bases on Guam were closed in the 1980’s.

• Several other species of snakes were known to live on Guam before 1950.

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