Ecology

The picture below shows a mimosa leaf before and after it was pinched.

• It is moving away from the pull of gravity.

• It is moving away from touch.

• It is moving toward touch.

• It is moving toward light.

Food Availability, Places to live, and water availability are all ______ of an Ecosystem.

• Biotic factors

• Heterotrophic factors

• limiting Factors

• Population factors

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The image shown is of a kelp bed. In ideal conditions, kelp can grow up to 18 inches per

day. In stark contrast to the slow-growing corals, the giant kelp canopies tower above the

ocean floor. Like trees in a forest, these giant algae provide food and shelter for thousands

of fish, invertebrates, and marine mammal species. Storms and weather events, like El

Niño, can tear and dislodge the kelp, leaving a tattered forest to begin its growth again

each spring. Sea otters and sea urchins play critical roles in the stable equilibrium of this

ecosystem. Sea urchins graze kelp and may reach population densities large enough to

destroy kelp forests at the rate of 30 feet per month. Urchins move in herds, and enough

urchins may remain in the location of a former kelp forest to stop any regrowth.

In the scenario above, identify the keystone and foundation species. Infer what might

happen if the keystone species were greatly reduced.

• Keystone species is the kelp. If the kelp is reduced or destroyed the basis for the entire

  ecosystem is destroyed as is the ecosystem.

• Keystone species is the kelp. It is the foundation for this ecosystem. If destroyed it would

  be replaced by another producer to establish a different ecosystem.

• Keystone species is the sea otter. Sea otters, playing a critical role in containing the

  urchin populations, prey on urchins and thus control the numbers of kelp grazers to

  maintain the forest.

• Keystone species is the sea urchin. If the sea urchin species is greatly reduced by an

  increase in the sea otter population, the kelp beds would continue to grow unchecked and

  other populations of herbivores would grow.

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The population of mice in a local forest ecosystem has recently died out due to disease. In

the past, these mice were the main predators of the forest beetles.

What is the best prediction about what will happen to the beetles?

• The drop in the mouse population will lead to a drop in the beetle population.

• The drop in the mouse population will lead to no change in the beetle population.

• The drop in the mouse population will lead to an increase in the beetle population.

• The increase in the mouse population will lead to an increase in the beetle population.

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When the members of a population reproduce at a constant rate and overshoot the

carrying capacity of their environment, it is called _______________ growth.

• logistic

• demographic

• exponential

• density dependent

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In an ecosystem, which is NOT a density-dependent limiting factor?

• predation

• parasitism

• competition

• natural disaster

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Choose the letter than correctly answers the question.

Which of the these is shown from the smallest to the largest?

• organism, population, community, ecosystem, biosphere

• biosphere, ecosystem, community, population, organism

• population, ecosystem, community, organism, biosphere

• community, ecosystem, biosphere, population, organism

Which of the following statements describes density-independent limiting factors?

• Competition is an example.

• Environmental extremes, such as a hurricane or drought, are examples.

• Their effects increase as the population increases in an area.

The drawings below show a young sunflower plant at different times of the day.

Which of the following describes the plant's movement?

• It bends away from the pull of gravity.

• It bends away from light.

• It bends toward light.

• It bends toward water.

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Which of the following statements on ecosystem stability is correct?

• Higher biodiversity in an ecosystem provides better stability.

• Multiple keystone species are important to ecological stability.

• Ocean ecosystems are far more stable than terrestrial ecosystems.

• Higher animal to plant ratios provides the most stable environment.

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