Practice Exam 1 - Environmental Science - page 232

25. C Tropical rainforests store the majority of their nutrients in vegetation. Therefore, the soil contains
minimal nutrients. The runoff from extensive rain in these regions also contributes to the removal of nu-
trients from the soil.
26. C The pollutant starts with a concentration of 0.5 ppm. The pollutant dissipates over a five-day period
by 20 percent. Twenty percent of 0.5 ppm is 0.5 × 0.20 = 0.1 ppm. And so, after five days, the concen-
tration is 0.4 ppm. But 20 percent of this is 0.08. So, after ten days, there is 0.32 ppm remaining.
Twenty percent of this is 0.064. So, after 15 days, there is 0.256, rounded to 0.26 ppm remaining.
27. B The sun supplies the energy that fuels the beginning of the food webs on Earth. Plants, algae, and
some bacteria use solar energy to make their own food in the process of photosynthesis. This process
also produces the chemical energy that serves as fuel for herbivores. Herbivores are then consumed by
carnivores, and so on. Without solar radiation, there would be no energy to start this process.
28. E The United States has the largest ecological footprint, consuming more resources, using more land,
using more water, and producing more waste than any other nation.
29. C An inverted population pyramid describes a population with more people in the older age brackets as
opposed to younger age brackets. This age structure has an impact on social and economic systems. So-
cially, this affects the labor market, military recruitment, and reproduction. An inverted population pyr-
amid also weighs heavily on social systems that support the elderly, such as Social Security and health-
care.
30. C Carrying capacity is the population that an ecosystem can support. In this case, the number of mule
deer exceeded that which the food supply could support. The starvation deaths of individuals brought
the population in line with the ecosystem's carrying capacity.
31. E The effects of China's one-child policy are in some ways different than they would be in other popu-
lations. Males are still valued more than females in Chinese culture, so it is desirable to have a son. So-
metimes people abort female fetuses because there are limits on having more than one child. This leads
to an uneven sex ratio. The policy also leads to an inverted population pyramid, with an inordinate per-
centage of elderly citizens, which increases pressures on healthcare and Social Security. Because there
are fewer young people in the country, there are fewer people entering the military.
32. D To find the growth rate of a population the following equation is used:
(Crude Birth Rate + Immigration) - (Crude Death Rate + Emigration) = Growth Rate per 1,000 Indi-
viduals
The answer is then multiplied by 100 to convert it to a percent. The terms crude birth rate and crude
death rate mean per 1,000 individuals.
For the question, calculate as follows:
Then convert it to a percent by multiplying by 100.
The answer is 2.1 percent.
33. E With a growth rate of 1.8 percent, the population is growing. In fact, the population will double in
about 39 years. If there is even a small positive growth rate, the population will continue to grow expo-
nentially.