Download Answers to Mastering Concepts Questions – Chapters 1 and 2

Answers to Mastering Concepts Questions
Chapter 42
42.1
1. 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. Deforestation results from humans burning and clearcutting forests, for lumber production or to
make room for human settlements or agriculture. In some areas, desertification follows removal
of tree cover or heavy grazing of grasslands.
3. Dams and channelization destroy habitats. 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.
4. 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.
5. Major sources of industrial smog include power plants, factories, and households that burn coal
and oil. Photochemical smog comes from emissions from vehicles. Coal-burning power plants are
major sources of acid deposition.
6. Here are the effects of different forms of air pollution on life:
- smog: injures plants and causes human respiratory problems;
- acid deposition: disrupts food webs in acid lakes, killing many species; may play a role in dieoffs of amphibians; kills forest trees;
- particulates: trigger inflammation, shortness of breath, asthma, cancer;
- thinning of the ozone layer: allows harmful UV radiation to reach Earth’s surface, causing an
increase in skin cancer and cataracts; kills phytoplankton at the base of food webs in aquatic
ecosystems; may be responsible for die-offs of amphibians
7. 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.
42.2
1. Human activities that contribute to a buildup in CO2 in the atmosphere include burning fossil
fuels and tropical deforestation.
2. During the 20th century Earth’s climate has changed as the atmospheric concentration of CO2
and average global temperatures have both increased.
3. Continued warming trends might cause migrations to occur earlier and/or change migration
paths. Distributions of species also will shift as Earth’s average temperature increases. Some
species will change their ranges, and others will go locally extinct.
42.3
1. Humans intentionally introduce nonnative species into new areas when they move their
households to new localities. Agriculture has intentionally moved many species of plants and
animals around the world. Accidental transport may also occur via ships, cars, and planes.
2. Invasive species are nonnative species that breed in the new location and spread widely.
Some are pest species, whereas others may harm human health or affect the economy. Invasive
species dominate an area in destructive ways and supplant native species, eventually excluding
them, sometimes preying upon them, and causing other native species to become extinct.
Nonnative species can carry diseases that kill native species.
3. Examples of species declines caused by overexploitation include the dodo, passenger pigeon,
Carolina parakeet, many 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.
42.4
1. 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. Five tools that conservation biologists use to preserve biodiversity are:
- preserving habitat: setting aside natural areas and protecting them from human interference and
destruction;
- reversing habitat destruction: restoration projects to reverse environmental damage;
- captive breeding programs: allow endangered species that have been raised in captivity to
repopulate wild environments;
- managing harvests: protects remaining stocks of overexploited species, allowing their numbers
to rebound;
- control of introduced predators: removes the pressure of predation from stressed populations of
their prey.
3. Scientists, government, and ordinary citizens can work together for conservation if everyone
does what he or she can to preserve diversity and support conservation efforts in everyday life.
Scientists contribute new information about species declines or recovery, and government
policies can influence the actions of individuals and corporations.