Ecosystem Stability

The overgrowth of algae poses a major problem for coral reefs. Intensive fishing is one factor that contributes to algae overgrowth because it does which of the following?

• Allows more sunlight to be available to algae

• Inhibits the spread of pathogens in algae colonies

• Reduces the number of organisms that feed on algae

• Increases the competition between different algae species

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Which of the following are missing from the food web shown above?

• Producers

• Decomposers

• Omnivores

• Predators

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The acacia ant nests and feeds in the plant’s hollow thorns. The ant helps protect the bullshorn acacia by attacking insects and grazing animals that come near the plant. The relationship between the acacia ant and the bullshorn acacia is an example of which of the following?

• Commensalism

• Mutalism

• Neutralism

• Parasitism

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The carbon cycle includes processes that release carbon into the atmosphere and places that act as carbon reservoirs. The diagram below shows both major processes that release carbon and major carbon reservoirs.

Which of these disruptions would cause an excess output in the carbon cycle?

• The destruction of terrestrial biota

• Increases in marine biota

• A reduction in the use of fossil fuels

• A thickening of ocean sediments

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The Nile River flows into the Mediterranean Sea. The Aswan High Dam contains the flow of water from the river and reduces the annual fall flooding. The floodwater is trapped behind the huge dam, allowing irrigation for agriculture. Sediments that would be washed away by the annual floods are also trapped behind the dam. The graph shows the water flow from the Nile that enters the Mediterranean Sea.

How has this dam most likely affected the Mediterranean Sea ecosystem?

• Reduced nutrients from the land support fewer producers in the sea.

• Water trapped behind the dam causes the marine ecosystem to move inland

• The flooding in August through November causes marine life to be destroyed.

• The water temperature of the sea has increased.

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The Texas blind salamander (Eurycea rathbuni) lives in the Edwards Aquifer region around San Marcos. Along with other species the salamander lives in total darkness in the underground crevices and caves of the aquifer region. The table lists some of the organisms that live in this environment and their food sources.

In an energy pyramid for these aquifer cave dwellers, which of the following would be placed at the bottom?

• Snails

• Blind shrimp

• Protozoa

• Texas blind salamander

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The iris controls the size and shape of the pupil. Which eye most likely belongs to an animal that is active most of the day on white desert sand?

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A native species and a non-native species are competing for resources within the same ecosystem. The non-native species is more likely to survive than the native species in which of the following situations?

• Both the native species and the non-native species thrive on the same food source.

• The native species is immune to certain pathogens in the ecosystem.

• Predators prey on both native and non-native species

• The non-native species has no natural enemies in the ecosystem.

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Which rhinoceros species is best adapted for feeding in the large open grasslands of Africa’s Serengeti ecosystem?

• Black rhinoceros

• White rhinoceros

• Sumatran rhinoceros

• Javan rhinoceros

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Dead zones are low-oxygen areas that develop on the seafloor. Scientists hypothesize that phytoplankton blooms cause these dead zones. Phytoplankton blooms occur when excess nutrients are introduced by pollution from fertilizers, sewage plants, and the burning of fossil fuels. Which of the following would most likely cause an increase in these contributors to dead zones?

• Rainfall patterns that increase freshwater runoff from terrestrial ecosystems

• Replacing coal-fired power plants with windmills

• Farming practices that reduce nitrate and phosphate applications

• Constructing efficient water-recovery and treatment plants

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