Practice Exam 1 - Environmental Science - page 237

79. B Eutrophication occurs when excess nutrients enter the water from runoff. When, as is frequently the
case, these nutrients are due to human sources including agriculture, sewage, urban areas, and industry,
it is considered cultural eutrophication.
80. B Industrial smog is created when coal is burned and carbon dioxide, carbon monoxide, and soot are
produced. Sulfur dioxide is produced from the combustion of sulfur-containing coal. Sulfur dioxide is
oxidized to sulfur trioxide, which can react with water, forming sulfuric acid. Sulfuric acid is a compon-
ent of industrial smog.
81. D Thermal pollution results from the heating of a water source beyond its natural temperature range,
commonly resulting from the release of water from a factory. Often, water is used to cool industrial pro-
cesses, thereby absorbing heat. When the water is discharged, it may still be hot or warm, thus heating
the water into which it is released. Thermal pollution can harm ecosystems by killing organisms and,
thus, affecting biodiversity, food webs, and ecosystem structure.
82. C During secondary treatment in the sewage treatment process, oxygen is added to start aerobic de-
composition. This results in the removal of most suspended solids, breaking down the organic matter.
83. B Point B represents the LD 50 , which is the lethal dose for 50 percent of the population. It corresponds
to the death of 50 percent of the population on the y -axis.
84. C The threshold value is the amount of a toxicant that begins to affect the population being tested.
Therefore, on the graph the threshold value is the point at which a response starts registering on the y -
axis, point C.
85. E Milankovitch cycles have an impact on the amount of solar radiation affecting various latitudes on
the Earth's surface. There are three different changes to the Earth's rotation; each change occurs in a
cycle between every 23,000 and 100,000 years, resulting in changes in climate.
86. D Resistance to a pesticide or other substance occurs over many generations through natural selection.
When a pesticide is applied to a crop, many insects die, but the ones that survive have a natural resist-
ance to the pesticide. More insects of the next generation survive because they have a natural resistance
inherited from their parents. Through selection acting across generations, the population gradually be-
comes more and more resistant until almost the entire population is resistant to the pesticide.
87. A The combustion of wood produces carbon monoxide and particulate matter in the form of ash. These
both can be health hazards; carbon monoxide can lead to cardiovascular disease or asphyxiation and
particulate pollutants can lead to irritation, asthma, respiratory issues, and cancer.
88. C Hazardous waste can be classified as ignitable if the substance can catch fire easily, reactive if the
chemical is unstable and can react with other compounds easily, corrosive if a substance can deteriorate
metal easily, or toxic if a chemical can harm human health.
89. D Coral reef ecosystems are especially sensitive to climate change. As water temperatures increase as a
result of global warming, the algae (zooxanthalae) that live in a mutualistic relationship with the coral
leave. This leaves the coral without food and nutrients, ultimately killing them.
90. C The integrated pest management (IPM) approach uses many techniques together to combat the threat
of pests. Techniques include crop rotation, habitat alteration, some chemical use, transgenic crops, and
biological controls. Because every method has negatives, combining the benefits of each leads to a
more successful and safer approach to pest management.
91. E With the changing climate, tropical diseases are having an impact on a broader scale. Because the
ranges of warm climate are increasing, tropical diseases are able to move into areas that previously