SB5 Ecology Review 2_Population Dynamics

A pond dries up over the course of a year as a result of a drought. What will most likely happen within the second year if the pond remains dry?

• Meadow grasses will grow on the bottom of the dried-up pond.

• Cacti will grow as the dried-up pond fills up with sand.

• A pine forest will replace the pond.

• No further change will occur.

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Read the passage below and answer the question(s) that follow. Passage Carrying Capacity and Limiting Factors Carrying capacity is defined as the number of organisms that an ecosystem can support. The carrying capacity is determined by limiting factors that determine the growth of populations within the ecosystem. Biotic limiting factors include the availability of food and competition with other organisms. Abiotic limiting factors include space, temperature, and the availability of water. The carrying capacity and the limiting factors of an ecosystem are related. A population will experience logistic growth due to limiting factors and experience exponential growth due to an absence of limiting factors, as shown in the graph. Which of the following is a biotic limiting factor?

• Space

• Temperature

• Availability of water

• Availability of food

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If the desert experiences a prolonged drought where many of the plants die, which BEST predicts the effect on the carrying capacity of the ecosystem?

• The carrying capacity of the ecosystem will decrease because there will be more space available for organisms.

• The carrying capacity of the ecosystem will increase because there will be fewer organisms that require resources.

• The carrying capacity of the ecosystem will decrease because there will be less food available for many organisms.

• The carrying capacity of the ecosystem will increase because there will be fewer organisms competing for resources.

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Over several years, biologists in a wildlife management area studied changes in the populations of deer and the plants they eat. Which statement best describes how deer affected the plant population over the course of the study?

• The plant population increased dramatically in response to an increase in the deer population.

• The deer and plant populations increased and decreased throughout the years, but did not affect each other's population.

• When the plant population decreased, this lead to a significant increase in the deer population.

• When the deer population increased significantly, the plant population decreased in response.

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Bees play a central role in the health of terrestrial ecosystems because they are vital to the pollination of plants. The extinction of bees could cause the collapse of plant-based terrestrial ecosystems. Based on this description, bees can best be described as a

• foundation species.

• native species.

• keystone species.

• specialist species.

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What would most likely occur over time if the burning and clearing of tropical rainforests stopped?

• an increase in the amount of oxygen released into the atmosphere

• a decrease in the biodiversity of species

• an increase in the amount of atmospheric pollution produced

• a decrease in the source of new medicines

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Read the passage about plankton algae. Plankton algae are microscopic algae that live in water. In a healthy pond ecosystem, plankton algae can be beneficial. They are fed on by zooplankton which, in turn, become food for fish. Plankton algae can grow rapidly when they are supplied with nutrients such as nitrogen and phosphorous. When fertilizer runs off from a farmer’s field into a nearby pond, the extra nutrients can cause the plankton algae to grow too quickly and form a bloom. The bloom of algae can cover the entire surface of the pond. Which two arguments correctly predict an effect of an algal bloom on the pond ecosystem?

• The temperature of the water will begin to increase.

• The amount of oxygen in the pond water will be lower.

• The fish population will increase with the added nutrients.

• The amount of carbon dioxide in the pond water will be lower.

• The underwater plants will not receive enough sunlight to grow.

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Which of the following processes must occur for a forest ecosystem to recover after a wildfire?

• development

• evolution

• succession

• mutualism

Scientists researching Pacific sea otters find that many members of the population are infected by a parasite, and a number of the sea otters must be destroyed to save the entire sea otter population. One of the main foods of sea otters is sea urchin, which eat kelp. The kelp forest is home to many species of fish. How is destroying some of the sea otters MOST LIKELY to affect fish living in the kelp forest?

• Destroying the sea otters will cause the fish population to increase.

• Destroying the sea otters will cause the fish population to become extinct.

• Destroying the sea otters will allow the fish population to remain constant.

• Destroying the sea otters will cause the fish population to decrease.

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Which of the following is NOT a density-dependent limiting factor?

• competition

• disease

• earthquake

• predation