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The Biosphere – Chapter 56
Key terms
Weather
Climate
Trophosphere
Stratosphere
Rain shadow effect
Upwelling
Biome
Savanna
Tropical rain forest
Temperate rain forest
Desert
Boreal forest
Taiga
Temperate deciduous forest
Tundra
Tropical seasonal forest
Grassland
Regional climate
Mediterranean climate
Photic zone
Aphotic zone
Neritic zone
Benthic zone
Pelagic zone
Littoral zone
Intertidal zone
Abyssal zone
Barrier islands
Estuaries
Mangrove swamps
Lakes
Ozone hole
Clean Air Act
Oxygen demanding wastes
Infectious agents
Harmful algal blooms
Sedimentation
Clean Air Act
Clean Water Act
Rivers
Ponds
Wetlands
Plankton
Nekton
Hydrothermal vents
Limnetic zone
Profundal zone
Epilimnion
Hypolimnion
Thermocline
Turnover
Eutrophic
Oligotrophic
Cultural eutrophication
Kyoto Protocol
Milpa or swidden agriculture
Genetically modified organisms (GMOs)
Integrated Pest Management (IPM)
Selective cutting
Clear cutting
Salinization
Industrial timber
Fuelwood
Endocrine disrupters
Urbanization
Urban sprawl
Smart growth
Pollution
Pesticide
Point source
Non-point source
Primary pollutant
Secondary pollutant
Particulate matter
Photochemical oxidants
Bioaccumulation
Biomagnification
Key concepts
Factors affecting temperature and precipitation
Climate and other effects of El Niño
Defining and distinguishing biomes
Cause and effects of global climate change
Stratospheric ozone depletion
Nutrient enrichment in aquatic and marine ecosystems
Outline of topics
56.1 Climate shapes the character of ecosystems.
Effects of the Sun and Atmospheric Circulation
• The tropics are warmer than temperate regions because the sun's rays arrive almost
perpendicular to equatorial regions. (p. 1204)
• High temperatures near the equator encourage evaporation and create warm, moist air,
causing large amounts of precipitation near the equator. (p. 1205)
• When the air masses reach about 30° north and south latitude, the cool, dry air sinks,
forming areas of low precipitation (deserts). (p. 1205)
Atmospheric Circulation, Precipitation, and Climate
• The rain shadow effect helps create deserts at places other than 30° north and south
latitude, as mountain ranges intercept moisture-laden winds and cause most of the
precipitation to fall on the windward side of the range, blocking moisture from the leeward
side. (p. 1206)
• Unique regional climates such as Mediterranean climates are also formed due to prevailing
winds such as the westerlies and the trade winds. (p. 1206)
• Temperature tends to vary according to latitude -- warm in the tropics, and cooler as you
move away -- and according to elevation, with temperature decreasing as elevation increases.
(p. 1207)
Effects of Oceans on Climates
• Oceans move heat energy around the globe and moderate climates.
• When the east-west trade winds in the Pacific Ocean slacken, warm water begins to move
back across the ocean from the coast of South America, causing a phenomenon called El Niño,
which widely influences the world's weather systems. (p. 1213)
56.2 Biomes are widespread terrestrial ecosystems.
The Major Biomes
• Biomes are major communities of organisms with a characteristic appearance that are
distributed over areas defined by temperature and precipitation differences. (p. 1208)
• Eight of the major biomes are tropical rain forest, seasonal tropical forest, savanna, desert,
temperate rainforest, grassland, temperate deciduous forest, boreal forest, taiga, and tundra.
(p. 1208)
• Each biome has a unique set of characteristics that define them.
• All biomes on earth are threatened by human activity.
56.3 Aquatic ecosystems cover much of the earth.
Marine Ecosystems
• The marine environment consists of three major habitats: the neritic zone (shallow water
containing most of the world's major fisheries), the pelagic zone (water above the ocean
floor), and the benthic zone (ocean floor). (p. 1214)
• Approximately 40% of all photosynthesis on earth is performed by photosynthetic plankton
in the oceans. (p. 1215)
Freshwater Ecosystems
• Freshwater habitats are much more limited in area than marine habitats. (p. 1216)
• Photosynthetic organisms are limited to the upper photic zone of ponds and lakes. (p. 1216)
• Ponds and lakes have three zones where organisms are found, which are distributed
according to the distance from shore: the littoral, limnetic, and profundal zones. (p. 1216)
• Thermal stratification is characteristic of larger lakes in temperate regions and seasonal
turnovers occur. (p. 1216)
• Eutrophic lakes contain an abundant supply of organic matter, while organic matter and
nutrients are relatively scarce in oligotrophic lakes. (p. 1217)
• Human activities can lead to the eutrophication of oligotrophic waters, a phenomenon known
as cultural eutrophicantion. (p. 1217)
• Wetlands are often very productive ecosystems that filter out pollutants and also serve as
water storage basins helping to moderate flooding. (p. 1217)
56.4 Human activity is placing the biosphere under increasing stress.
Carbon Dioxide and Global Warming
• The greenhouse effect is caused when carbon dioxide and other gases allow shortwavelength solar radiation into the atmosphere, but trap longer-wavelength heat radiation
from escaping, thus warming the earth's atmosphere. (p. 1222)
• In the 1990s, the scientific community reached a consensus that the earth's average
temperature is increasing, and human-related greenhouse gases are the major cause of the
increase. (p. 1222)
• The effects of global warming on natural ecosystems may include the shifting of the
geographic distribution of organisms tracking environmental conditions, as well as life cycle
changes to adapt to changing environmental conditions. (p. 1223)
• Continued global warming may also influence human conditions due to rising sea levels,
effects on agriculture, and human health issues. (p. 1224)
Destruction of Forests
• More than half of the world's human population lives in the tropics. This percentage is
increasing, placing greater stress on tropical forests, areas of very high biodiversity. (p. 1220)
• Rain forests grow on poor soil, thus they can become hard to regenerate once they are
cleared. (p. 1220)
• Milpa or swidden agriculture is a sustainable land use provided that rotation times between
crops is 12-15 years.
• Increasingly, larger numbers of people moving into tropical areas are clearing larger areas of
rain forest. (p. 1220)
• Half of the world’s forest resources are used for industrial timber while half is used for
fuelwood. Most of the production of industrial timber occurs in the developed world, while
most of the production occurs in the developing world.
• Clearcutting is very efficient and easy to implement, yet is less sustainable than selective
cutting. Sustainable forestry allows use of forest resources at a rate no faster than they can
be regenerated.
Agriculture
•Widespread modern agriculture introduces large amounts of new chemicals into the global
ecosystem, including pesticides, herbicides, energy and fertilizers. (p. 1218)
• Genetically modified organisms contain DNA from an unrelated organism and can increase
agricultural production. There are still concerns about the use of GMOs.
• Pesticides, while increasing yields, can have negative impacts through effects on non-target
organisms, evolution of pesticide resistance, and contamination of the environment.
• Biological control, natural pesticides, integrated pest management and sustainable
agriculture provide solutions to the negative impacts of synthetic pesticides.
Urbanization
• Over the course of history, humans have moved from rural areas to urban areas, a process
known as urbanization.
• In the developing world, urban sprawl is the leading problem with urbanization, as housing
tracts consume valuable farmland. The problems with urban sprawl include reliance on the
automobile and loss of livable cities, as well as economic and racial segregation.
• Smart growth provides a solution to urban sprawl, allowing compatible use of land for
environmental protection and human habitation.
Pollution
• Air pollutants, such as sulfur, particulate matter, nitrogen oxides, heavy metals, and ozone
have negative environmental impacts and can be carried long distances.
• Stable, long-lasting chlorinated hydrocarbons such as DDT can become increasingly
concentrated in an ecosystem due to bioaccumulation followed by biological magnification or
biomagnification. (p. 1218)
• Industrial pollution contains many chemicals. For example, sulfur, when introduced into the
upper atmosphere, can combine with water vapor to produce sulfuric acid, which can fall to
the ground in many forms, including snow and rain. (p. 1219)
• Precipitation with an acidic pH can cause many environmental problems, including lake
acidification and forest damage. (p. 1219)
• Industrial chlorofluorocarbons (CFCs) released into the atmosphere for many decades have
led to a thinning of the earth's stratospheric ozone layer, which shields the planet from
harmful ultraviolet radiation. (p. 1221)
• Infectious diseases, oxygen demanding wastes, nutrient enrichment and sedimentation are
causes of water pollution.
• The Clean Air Act and Clean Water Act are two pieces of legislation that seek to improve
environmental quality, with a focus on human health.