Download Answers to Mastering Concepts Questions – Chapters 1 and 2

Answers to Mastering Concepts Questions
20.1
1. What is the value of diversity to humans and to ecosystems as a whole?
Humans and ecosystems as a whole depend upon many diverse organisms to survive.
Biodiversity is necessary for the health of Earth’s food chains and food webs (some of
which include humans), maintenance of its biogeochemical cycles, and prevention of
flooding and soil erosion.
2. Describe the three types of biodiversity.
Genetic biodiversity is the amount of genetic variation in a species. Species biodiversity
is the number of species in the biosphere. Ecosystem biodiversity accounts for the
different types of ecosystems on earth.
3. Differentiate among extinct, endangered, and vulnerable species.
Extinct species no longer exist. Endangered species are at high risk for extinction in the
near future, and vulnerable species are likely to become extinct in the distant future.
4. What is conservation biology?
Conservation biology is the study of diversity at all levels, with the goal of understanding
why species go extinct and preventing this outcome.
20.2
1. Which human activities account for most of the loss of terrestrial habitat?
Habitat destruction comes from farming and urban growth, which results in deforestation
and desertification.
2. How do dams and channelization alter river ecosystems?
Dams flood some areas and deprive others of water, and they change the qualities of
water such as its temperature, oxygen content, and nutrient content. Channelization
destroys habits by removing streamside habitat and changing the rate at which water
flows. As water moves more quickly, sediments are flushed further downstream, often
carried many miles to be deposited at the mouth of a river.
3. Why is damage to estuaries and coastlines especially devastating?
Estuaries are places where larvae and young of many species of sea life shelter and grow
until they can move upstream to rivers, or into ocean waters. Damaging estuaries kills
many forms of life at their developmental stages. Coastal habitats support a variety of
our commercially important species and are highly developed for recreation and
urbanization.
20.3
1. How do pollutants affect aquatic ecosystems?
Toxic chemicals may persist and be biologically magnified as they move up food chains,
eventually causing cancer and disturbing reproduction in some species. Excess nutrients
in an aquatic ecosystem cause eutrophication, which causes O2 depletion and kills many
aquatic organisms. Sediments block the penetration of light and reduce photosynthesis in
aquatic ecosystems. Excess heat reduces the oxygen-carrying potential of water and may
kill aquatic organisms.
2. What are major sources of smog, and acid deposition?
Major sources of smog include power plants, factories, households that burn coal and oil,
and emissions from vehicles. Coal-burning power plants are major sources of acid
deposition.
3. What effects does the thinning ozone layer have on life?
The thinning of the ozone layer allows harmful UV radiation to reach Earth’s surface,
causing an increase in skin cancer and cataracts. UV radiation also kills phytoplankton at
the base of food webs in aquatic ecosystems, and may be partly responsible for die-offs
of amphibians.
20.4
1. Why is CO2 accumulating in Earth’s atmosphere?
Excess CO2 is accumulating from the burning of fossil fuels and from tropical
deforestation.
2. Describe how and why Earth’s climate changed during the past century.
During the 20th century, Earth’s climate changed as the atmospheric concentration of CO2
and average global temperatures have both increased.
3. How does global climate change threaten biodiversity?
Species are adapted to their current environments. Climate change that causes rapid
ecosystem changes may cause many species to go extinct if they cannot migrate to new
areas.
20.5
1. What features characterize an invasive species?
An invasive species breeds easily and spreads widely from its point of introduction; it
also causes damage to the environment.
2. How do invasive species disrupt ecosystems?
Invasive species can prey on other species, reduce the availability of sunlight, destroy the
tissues of native plants or animals, or displace native species.
3. List examples of species declines caused by overexploitation.
Examples of species declines caused by overexploitation include the dodo, passenger
pigeon, Carolina parakeet, commercially fished species such as tuna, flounder, halibut,
swordfish, and cod, and many species that are not targets of commercial fishing, but that,
nevertheless, are harmed by its practices. These include marine mammals, marine
invertebrates, seabirds, sea turtles, and many species of fishes that are used as food for
farmed salmon and shrimp.
20.6
1. How does human population growth affect conservation biology?
As the human population grows, it exerts increased pressures on natural resources.
Biodiversity suffers. So, as the human population continues to grow, conservation
biology becomes increasingly important in the attempt to preserve biodiversity.
2. List and describe seven tools that conservation biologists use to preserve biodiversity.
(1) Set aside protected habitat. (2) Reverse habitat destruction. (3) Captive breeding and
reintroduction to help increase population numbers. (4) Manage harvests, reducing the
numbers of organisms taken in a year. (5) Predator control. (6) Biotechnology, perhaps to
clone extinct or endangered organisms or to identify undiluted gene pools in the wild. (7)
Develop ecotourism and other economic incentives for preservation.
3. How can scientists, governments, and ordinary citizens work together for
conservation?
Scientists contribute new information about species declines or recovery, and government
policies can influence the actions of individuals and corporations. Ordinary citizens can
support conservation efforts in everyday life.
20.7
1. Summarize the evidence that climate change is a factor in the extinction of harlequin
frogs.
All the extinct species came from the midland elevations where some cloud cover is
normal. Coinciding with the extinctions was a change in climate such that the days were
cooler and the nights warmer, creating a thicker cloud cover. The decrease in sunny
patches may have helped a skin fungus flourish.
2. Other than climate change, what is an alternative hypothesis that could explain that
extinction of harlequin frogs? How would you test your hypothesis?
[Answers will vary.]
Answers to Write It Out Questions
1. List the main threats to biodiversity worldwide.
Habitat destruction, pollution, global climate change, invasive species, and
overexploitation are the main threats.
2. Which human activities promote habitat destruction?
Human activities that promote habitat destruction include deforestation, desertification,
alterations of rivers’ paths, pollution, and many other activities.
3. Visit the waterfootprint.org website to see how much water is required to produce
various foods and beverages. Why might it be important for an individual to choose
products with a low water footprint?
[Answers will vary.]
4. How does the combustion of fossil fuels influence such different phenomena as acid
deposition and global climate change?
The combustion of fossil fuels releases sulfur and nitrogen oxides into the atmosphere,
where they join water and form sulfuric acid and nitric acid. These acids then return to
the Earth as acid deposition. At the same time, fossil fuel combustion also releases CO2,
a greenhouse gas that traps warmth near Earth’s surface.
5. In what ways is the greenhouse effect both beneficial and detrimental?
The greenhouse effect supports life, because Earth’s average temperature would be much
lower without its blanket of greenhouse gases. As CO2 accumulates in the atmosphere,
however, average global temperatures are rising. Changes in temperature or moisture can
alter populations, kill some organisms outright, stress others, or cause migrations.
Continued climate change will affect not only wild organisms, but also agriculture and
public health.
6. Explain the logic behind planting trees as a way to reduce global climate change.
Trees use CO2 in photosynthesis, incorporating much of it into long-lasting wood. They
can, therefore, temporarily help offset the release of CO2 into the atmosphere from the
burning of fossil fuels. Planting trees can also help offset the loss of trees from
deforestation.
7. Why are invasive species harmful?
Invasive species change the composition of a community. They also carry diseases that
spread to native species. Efforts to eradicate invasive species are expensive.
8. List three ways you can alter your lifestyle to promote conservation.
Many answers are possible, but three ways you can alter your lifestyle are choosing foods
and products that reflect sustainable practices, encouraging manufacturers to change
packaging to reduce threats to wildlife, and paying attention to what you discard and pour
down the drain.
9. Search the Internet for information on the Convention on Biological Diversity and on
the international agreement called CITES. How does each approach tackle the
biodiversity crisis on a global scale?
The Convention on Biological Diversity covers all three levels of diversity and seeks not
only to conserve diversity, but also to manage resources sustainably, and to equitably
share genetic resources. CITES is an international trade agreement concerning
endangered species, which makes its focus largely at the species level of diversity.
10. Give an example of an environmental problem that can immediately reduce
biodiversity and one that has a delayed effect.
An environmental problem that can immediately reduce biodiversity is changing a river’s
path, which can cause stream bank erosion and choke out downstream communities. An
environmental problem that has a delayed effect is global climate change; CO2 released
into the air has caused the average global temperature to rise gradually.
Answers to Pull it Together Questions
1. What are examples of pollutants in air and in water? Which of these pollutants
eventually reach land?
Many examples are possible; this is one correct answer. Pollutants in air include
particulates such as soot and methane gas from bovine herds. The soot gradually falls
back onto the land, but the methane remains in the atmosphere. Examples of water
pollutants include sewage. After water treatment, the solid waste remaining is often
spread onto land. Plastics can also be water pollutants that can wash ashore.
2. How does human population growth contribute to each of the main factors causing
species extinctions?
Habitat destruction, pollution, global climate change, invasive species, and
overexploitation are the main threats to biodiversity. As our population grows, we use
more land, reducing available habitat. Additional pollution is another inevitable
consequence of population growth. We also continue to expand the intentional and
accidental global trafficking of other species, and in doing so, we increase the
introduction of invasive species. People and industry demand energy, which currently
comes from fossil fuels; an expanding human population, therefore, means more CO2
emissions and more climate change. Finally, a greater population means greater demand
for all resources, including overexploited species.
3. What are some examples of conservation tools other than those illustrated in this
concept map?
You could set aside protected habitat; develop a captive breeding and reintroduction
program to help increase population numbers; control predators and invasive species; or
develop an ecotourism project.
4. Which tools save entire ecosystems? Which target individual species?
Captive breeding, reintroduction, and harvest regulation target individual species while
the others save ecosystems.