Biology SB5

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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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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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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If two species of organisms occupy the same niche ____________

• one will find a new habitat.

• competition will be very intense.

• both organisms will become extinct.

• both will need to enlarge their habitat.

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What impact do the amounts of available energy, water, and oxygen have on an

ecosystem?

• They are used as nutrients by living organisms.

• They recycle the residue of dead organisms.

• They control the environment's energy source.

• They act as limiting factors on the organisms.

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Alligators will use their powerful feet, tail, and snouts to dig a hole through the mud, producing small ponds known as "alligator holes." Many other species benefit from alligator holes. During the dry season, fish, turtles, and other aquatic animals live in the alligator holes. Birds, terrestrial animals, and plants use these holes as a source of water. What term best describes the role of alligators in this ecosystem?

• invasive exotic species

• keystone species

• producer

• primary consumer

A graph representing a population growth curve is shown

What does B represent on this growth curve?

• a population's carrying capacity

• exponential growth within a population

• linear growth within a population

• the lag phase of a population's growth

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Which statement below best explains what might have occurred to the population of insects at point A?

• The health of the insects improved, causing the population to stabilize.

• A predator was introduced, causing a decline in population growth.

• The population growth decreased as individual insects aged.

• The population reached a carrying capacity and stabilized.

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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.