Human Impact -23

A major environmental concern in urban areas is pollution produced by automobiles. Fluids, such as oil and gasoline, may leak out of vehicles and end up in lakes, streams, and rivers. One reason why scientists are concerned about this type of pollution is that

• the presence of these

  fluids in waterways could make them uninhabitable for aquatic organisms and reduce water supplies for humans

• the addition of these fluids will cause an increase in the levels of lakes and rivers, possibly causing

  flooding in nearby areas

• these fluids increase the rate of photosynthesis in aquatic plants, reducing the amount of O2 available for other life forms

• the addition of these chemicals to waterways reduces air quality, which would lead to increased respiratory diseases and global warming

Destruction of ocean habitats by pollution today means that the organisms living there may not survive in the future. By polluting the oceans, humans are

• helping advance economic gains by using resources wisely

• altering the equilibrium of ocean ecosystems

• decreasing the rate of species extinction

• increasing the stability of the oceans

Human society has become increasingly dependent on industry and technology. While this has had many benefits, it also has had the disadvantage of

• reducing the amount of food that can be produced by one acre of farmland

• lowering the level of carbon dioxide available for plants to use for photosynthesis

• raising the number of producers worldwide to dangerous levels

• increasing our reliance on energy sources such as fossil fuels

Direct harvesting occurs when

• pine trees are cut from a forest for use as lumber

• corn is planted in a newly plowed field

• zebra mussels are accidentally imported to the Great Lakes

• zebra mussels are accidentally imported to the Great Lakes

In New York State, it is common for farmers to plant large fields of one crop, such as the cornfield shown .

A negative outcome of this practice is that

• the corn will interbreed with weeds in the area

• new predators will be introduced into the ecosystem

• the stability of the ecosystem will be reduced

• new species of insect-resistant corn will evolve

Humans are able to positively or negatively affect their environment in many ways. Which statement accurately describes one of these possible effects?

• A positive environmental effect is that burning fossil fuels to generate electricity reduces carbon dioxide levels in the atmosphere.

• A positive environmental effect is the cutting of trees in rain forests to provide large quantities of lumber to build homes for the increasing world population.

• A negative environmental effect is that industrialization provides many jobs and helps the economy grow.

• A negative environmental effect is that unregulated fishing in the ocean can disrupt the interactions between organisms in existing food webs.

Dead zones are areas found in the oceans and some large lakes where there is not enough oxygen to support life. Algae blooms occur when excess nutrients are introduced as pollutants from fertilizers, sewage-treatment plants, and the burning of fossil fuels. When the algae die and undergo decay, bacteria rapidly use up the oxygen in the area. Which human activity would most likely result in a decrease in the size and number of dead zones?

• irrigating fields and lawns to increase runoff into the ocean and rivers

• building more coal-fired electrical generating plants

• reducing the use of chemicals on farm fields and golf courses

• constructing more sewage-treatment plants on the shores of lakes and rivers

A recent study found high levels of the toxic industrial pollutant mercury in the feathers of some songbirds. Those birds sang shorter, simpler versions of the songs they use to attract mates. Which statement regarding this finding is supported by the study?

• Mercury pollution will result in the extinction of all songbirds.

• Mercury prevents songbirds from obtaining required nutrients.

• Human activities usually affect the smallest animals in ecosystems.

• Human activities can have negative effects on a species.

In 2013, biologists encouraged nations to decrease the number of fish caught in order to help global fish populations recover. This seems to be helping some fish populations to increase. This increase in the size of some fish populations is a result of human

• actions that killed many of the predators of these fish populations

• decisions that weighed the need for food with the need to maintain fish populations

• activities that are increasing the use of nonrenewable resources of the oceans

• decisions that are increasing the use of renewable ocean resources

A decrease in the biodiversity of an ecosystem usually leads to

• an increase in predator and prey populations

• the elimination of material cycling

• a decrease in stability

• an increase in dynamic equilibrium