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Concept 8-2 Saltwater ecosystems are irreplaceable reservoirs
of biodiversity and provide major ecological and economic
services.
Concept 8-3 Human activities threaten aquatic biodiversity and
disrupt ecological and economic services provided by saltwater
systems.
Concept 8-4 Freshwater ecosystems provide major ecological
and economic services and are irreplaceable reservoirs of biodi-
versity.
Concept 8-5 Human activities threaten biodiversity and disrupt
ecological and economic services provided by freshwater lakes,
rivers, and wetlands.CHAPTER 9 Sustaining Biodiversity:
The Species Approach
Concept 9-1A We are degrading and destroying biodiversity in
many parts of the world, and these threats are increasing.
Concept 9-1B Species are becoming extinct 100 to 1,000 times
faster than they were before modern humans arrived on the
earth (the background rate), and by the end of this century, the
extinction rate is expected to be 10,000 times the background
rate.
Concept 9-2 We should prevent the premature extinction of
wild species because of the economic and ecological services they
provide and because they have a right to exist regardless of their
usefulness to us.
Concept 9-3 The greatest threats to any species are (in order)
loss or degradation of its habitat, harmful invasive species, hu-
man population growth, pollution, climate change, and overex-
ploitation.
Concept 9-4A We can use existing environmental laws and
treaties and work to enact new laws designed to prevent prema-
ture species extinction and protect overall biodiversity.
Concept 9-4B We can help to prevent premature species extinc-
tion by creating and maintaining wildlife refuges, gene banks,
botanical gardens, zoos, and aquariums.
Concept 9-4C According to the precautionary principle, we
should take measures to prevent or reduce harm to the
environment and to human health, even if some of the
cause-and-effect relationships have not been fully established,
scientifi cally.CHAPTER 10 Sustaining Terrestrial Biodiversity:
The Ecosystem Approach
Concept 10-1A Forest ecosystems provide ecological services far
greater in value than the value of raw materials obtained from
forests.
Concept 10-1B Unsustainable cutting and burning of forests,
along with diseases and insects, made worse by global warming,
are the chief threats to forest ecosystems.
Concept 10-1C Tropical deforestation is a potentially cata-
strophic problem because of the vital ecological services at risk,
the high rate of tropical deforestation, and its growing contribu-
tion to global warming.
Concept 10-2 We can sustain forests by emphasizing the eco-
nomic value of their ecological services, protecting old-growth
forests, harvesting trees no faster than they are replenished, and
using sustainable substitute resources.
Concept 10-3 We can sustain the productivity of grasslands by
controlling the number and distribution of grazing livestock and
by restoring degraded grasslands.Concept 4-6A Each species plays a specifi c ecological role called
its niche.Any given species may play one or more of fi ve impor-
tant roles—native, nonnative, indicator, keystone, or foundation-
roles—in a particular ecosystem.CHAPTER 5 Biodiversity, Species Interactions,
and Population Control
Concept 5-1 Five types of species interactions—competition,
predation, parasitism, mutualism, and commensalism—affect
the resource use and population sizes of the species in an ecosys-
tem.
Concept 5-2 Some species develop adaptations that allow them
to reduce or avoid competition with other species for resources.Concept 5-3 No population can continue to grow indefi nitely
because of limitations on resources and because of competition
among species for those resources.
Concept 5-4 The structure and species composition of commu-
nities and ecosystems change in response to changing environ-
mental conditions through a process called ecological succession.CHAPTER 6 The Human Population and
Its Impact
Concept 6-1 We do not know how long we can continue
increasing the earth’s carrying capacity for humans without seri-
ously degrading the life-support system for humans and many
other species.
Concept 6-2A Population size increases because of births and
immigration and decreases through deaths and emigration.Concept 6-2B The average number of children born to women
in a population (total fertility rate) is the key factor that determines
population size.
Concept 6-3 The numbers of males and females in young,
middle, and older age groups determine how fast a population
grows or declines.
Concept 6-4 Experience indicates that the most effective ways
to slow human population growth are to encourage family plan-
ning, to reduce poverty, and to elevate the status of women.CHAPTER 7 Climate and Terrestrial Biodiversity
Concept 7-1 An area’s climate is determined mostly by solar
radiation, the earth’s rotation, global patterns of air and water
movement, gases in the atmosphere, and the earth’s surface
features.
Concept 7-2 Differences in average annual precipitation and
temperature lead to the formation of tropical, temperate, and
cold deserts, grasslands, and forests, and largely determine their
locations.
Concept 7-3 In many areas, human activities are impairing
ecological and economic services provided by the earth’s deserts,
grasslands, forests, and mountains.CHAPTER 8 Aquatic Biodiversity
Concept 8-1A Saltwater and freshwater aquatic life zones cover
almost three-fourths of the earth’s surface with oceans dominat-
ing the planet.
Concept 8-1B The key factors determining biodiversity in
aquatic systems are temperature, dissolved oxygen content, avail-
ability of food, and availability of light and nutrients necessary
for photosynthesis.