Biology Human Impact

The presence of wastes, such as plastic bags and motor oil, in lakes and streams miles away from developed areas suggests that

• ecosystems are interconnected and human action can alter ecosystem equilibrium.

• recycling programs have failed to conserve biotic resources.

• natural processes can alter ecosystem stability.

• direct harvesting practices have led to irreversible destruction of ecosystems.

Answer explanation

Human impacts on the environment can be far-reaching. What we do in our own area of the Earth, can effect what happens in other areas as well.

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DDT and other pesticides used over 50 years ago are still affecting the environment today. Scientists have found these substances in recent glacier runoff. Glacier runoff occurs during the summer, when precipitation that has fallen on glaciers during the winter is released. Ice layers from existing glaciers have been analyzed. The results of this analysis show that the concentrations of DDT and other pesticides were highest about 10 years after the use of these substances was banned. This information shows that

• DDT and other pesticides cause glacier runoff during the summer.

• it takes humans over 50 years to analyze a glacier.

• precipitation helps to break down pesticides.

• the decision of one human generation may have an impact on future generations.

Answer explanation

the decision of one human generation may have an impact on future generations.

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The northern elephant seal was almost hunted to extinction in the 1800s. By the late 1890s, approximately one hundred seals were left, reducing the gene pool of the population. What will be the consequence of this reduction?

• Competition within the population will increase.

• The surviving elephant seals will be better able to adapt.

• Inbreeding will be less frequent among the remaining population.

• The elephant seals will be more vulnerable to environmental change. 

Answer explanation

The more genetic variation a population has, the more easily the population can deal with environmental change. If the gene pool decreases, genetic variation decreases.

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When fertilizers run off farmland into streams and ponds, the nitrogen content of the water increases. This can lead to rapid growth of algae in a process called eutrophication. How can this process affect other organisms in the water?

• Oxygen is used up as algae is decomposed, reducing the amount available to other organisms. 

• The water becomes better able to support aerobic organisms.

• The algae provide food for fishes and other organisms, leading to decreased algae populations. 

• The extra nitrogen provides additional food for the other organisms, increasing their population.

Answer explanation

Algal blooms, often caused by high levels of nitrogen in water lead to low dissolved oxygen levels and the death of many species in these ecosystems.

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A strip mining company wants to lease some land that is currently part of a national park. They promise to reclaim the land should any minerals be mined from the area, and they are willing to pay top dollar for the rights. As an ecologist, what factors would you raise with the local government? 

• the threat to local biodiversity

• management of the land after the company leaves

• the new jobs that would be created

• the increased traffic in the area

Answer explanation

Any time land is modified from its original natural state, the local organisms will be affected.

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Which best explains how livestock farming contributes to global warming ? Animals __________

• waste pollutes the soil

• are consuming too much grass

• decayed matter emits too much carbon dioxide

• produce methane when they are digesting food

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Why are forests important in reducing climate change? Trees ____

• use Carbon Dioxide to make food & release oxygen into the atmoshpere

• provide building materials

• are an important food source

• reflect all sunlight away from the Earth

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What is the primary impact of deforestation on the carbon cycle?

• Increases carbon sequestration

• Decreases atmospheric carbon dioxide

• Increases atmospheric carbon dioxide

• Decreases carbon emissions

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How does urbanization affect local wildlife populations?

• Increases biodiversity

• Decreases habitat fragmentation

• Increases habitat availability

• Decreases biodiversity

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Which of the following is a consequence of ocean acidification?

• Increased fish populations

• Coral bleaching

• Decreased sea levels

• Enhanced marine biodiversity

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