Chapter 19 Answers to Discussion Questions

Chapter 19
Answers to Discussion Questions
1. An island will have a limited amount of resources that must be shared among all individuals of the
island ecosystem. Size is important because usually the bigger an island is, the more diverse the habitat
and the more different ecological niches there will be for different species to occupy. Different organisms
will compete for dominance in their preferred ecological niche.
2. Energy is evident in all living and nonliving components of an ecosystem and in the interactions
between the components. Sunlight and wind are energy resources, potential energy is found in plant and
animal matter, temperature is related to thermal energy. Therefore energy influences what types of plants
and animals will be found in the ecosystem. Food chains cycle nutrients within an ecosystem and provide
the mechanism for energy to flow through the ecosystem.
3. Polar ice caps might begin to melt which would raise sea levels and cause flooding of shoreline areas of
countries bordering on oceans and of islands as well. Changes in agricultural practices could help slow
global warming. As crops become more productive, more sunlight is reflected. A recent trend toward less
frequent plowing of fields also has raised the reflectivity, or albedo, of the surface. Each of these factors
can cool local temperature. Irrigation cools the surface through a different effect – by increasing the
amount of energy used to evaporate water rather than heat the land.
4. Answers to this will vary depending on students' attitudes toward experimenting with natural
ecosystems. Some might think it was ethical because it was as close to a controlled investigation of an
ecosystem as one could hope to get, and could therefore provide a more realistic appraisal of what kinds
of interactions go on between established species and species which migrate into the ecosystem. Others
may feel that it's simply not right to destroy a whole ecosystem to investigate ecological problems.
5. Because organisms are interconnected and interdependent, it is impossible to change only one variable
without possibly also affecting many other variables. Changing only one variable at a time enables the
reproduction of a given solution to a specific problem. If more than one variable is simultaneously altered,
the problem might be solved, but identifying the specific change that eliminated the symptom becomes far
more difficult and will not help solve the same problem if it occurs in the future.
6. Answers will vary greatly. Everyone will have consumed resources: food, energy, and other materials.
Everyone will have added to pollution of the air and water directly (cars and buses) and indirectly
(electrical generation). The environment affects us most directly by defining the choices available to us:
weather determines how we dress, available foods determine what we eat, etc. Students may also reflect
on spiritual and emotional interactions with the environment.
7. If we really got serious about reducing air pollution, cars would have to be made much more efficient
and power plants would have to take greater steps to prevent the escape of pollutants. All of this will cost
more money which will be passed on to the consumer and/or companies will cut back jobs to help pay the
greater costs of pollution control. This will affect sectors of the economy supported by the power and
automobile industries negatively, but could stimulate growth in other sectors, such as in solar power
technology or mass transportation. There will be social problems as people become unemployed or
uprooted to take new jobs. Probably people will form political groups to resist changes that are going to
cost jobs, and industries will lobby against changes that are going to reduce their profits.
8. It would take 30-50 years for a new source of energy to work its way into the economy if the same time
spans are involved as in the transitions from wood to coal and coal to gas and oil. Factors that would

make this transition possible are increasing costs of decreasing supplies of fossil fuels and the
development of a solar energy technology that is competitively priced compared to fossil fuel energy.
9. A forest ecosystem, which is threatened with air pollution and urbanization.
10. Electrical cars obtain their energy from electricity, much of which is probably produced in a coal or
oil burning power plant. Indirectly, they do cause pollution because they depend on fossil fueled power
plants, which produce air pollution. Some prototypes have been developed to use solar generated
electricity and new hybrid cars have batteries that recharge by capturing energy of braking.
11. We would have no control over a change in the Sun’s temperature. At least two responses are
possible. Global warming is “natural,” and beyond our control; we need to develop policies to cope with
the inevitable changes. Alternatively, we might choose to attempt to actively counteract the Sun’s change.
12.The nonliving, or physical components of an ecosystem include the sun's energy, water, air
(atmospheric gases), rock and landforms. Soil is composed of living (plant and animal detritus) and
nonliving (rock particle) components. Each community consists of the plant and animal species best
suited to the nonliving components of the area. These nonliving components such as erosion and soil
quality can impact habitat, duration of sunlight can impact photosynthesis, and air quality can impact
plants and animals reliance on oxygen in the air for survival. The shape of the land will cause water to be
more plentiful in some areas, which will also limit the living components.
13. The concept of homeostasis was developed in 1851 by French physiologist Claude Bernard, referring
to internal dynamic constancy. In 1929 Walter B. Cannon coined the term “homeostasis.” It means a
stable state of the internal environment that is maintained by regulatory processes despite changes that
may occur in the external environment. It is virtually impossible to alter one aspect of an ecosystem
without other changes following in sometimes, unpredictable ways. This law of unintended consequences
could throw an ecosystem out of balance or homeostasis.
14. Methane is capable of trapping 25 times more heat than CO2, and is expected to cause approximately
16% of the global warming over the next 50 years. Evidence suggests that cow & pig flatulence and
decaying manure are the largest contributors of methane. According to the EPA, livestock "produce about
80 million metric tons of methane annually."
15. A microclimate is a local external atmospheric zone where the climate differs from the surrounding
area. Microclimates in an ecosystem can offer an opportunity for growing for crops or small area of
habitat for animals that would not otherwise thrive in the broader area, thus increasing the biodiversity of
the ecosystem.
Answers to Problems
1. Since for roughly every half degree Celsius increase in temperature, a global line of a temperature will
move 100 miles north; when there is a warming of one degree Celsius, my town will have the average
temperature of a town that is located 200 miles to the south.
2. Assume Yankee Stadium is a cube with dimensions 300 x 300 x 50 feet. Then the volume is 1.5 x 106
cubic feet. 1.5 x 106 ÷ 1000 So you would fill it in 1.5 x 103 years. Assume Grand Canyon is a rectangular
box with dimensions 2,722 feet depth x 48 miles long (x 5,280 feet/mile) and average width of 500 feet.
The volume is 3.4 x 1011 cubic feet ÷ 1,000 feet/yr. So you would fill it in 3.4 x 108 years. Viewed another
way, the trash Americans produce in one year fills the Grand Canyon.