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Ecology and the Biosphere
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Biology and Society:
Penguins and Polar Bears in Peril
• The scientific debate is over.
• The great majority of scientists now agree that the
global climate is changing.
• Average global temperatures have risen 0.8C
(about 1.4F) over the past century, mostly over
the last 30 years.
• Precipitation patterns have also changed, bringing
– longer and more intense drought to some regions
and
– flooding to other areas.
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Figure 18.0
Biology and Society:
Penguins and Polar Bears in Peril
• Overwhelming evidence indicates that human
enterprises are responsible for the changes that
are occurring.
• Our response to this crisis will determine whether
circumstances improve or worsen.
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AN OVERVIEW OF ECOLOGY
• Ecology is the scientific study of the interactions
between organisms and their environments.
• Humans have always had an interest in other
organisms and their environments.
• Extraordinary insight can be gained from a
discovery-based approach of
– watching nature and
– recording its structure and processes.
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Figure 18.1
Ecology and Environmentalism
• Technological innovations have enabled people to
colonize almost every environment on Earth.
• Earth’s resources
– affect our survival and
– have been greatly affected by our activities.
• Environmental problems
– can be understood by the science of ecology and
– require decisions based on values and ethics.
• On a personal level, each of us makes daily
choices that affect our ecological impact.
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Figure 18.2
A Hierarchy of Interactions
• Many different factors can potentially affect an
organism’s interaction with the environment.
– Biotic factors are
– all of the organisms in the area and
– the living component of the environment.
– Abiotic factors
– are the environment’s nonliving component and
– include chemical and physical factors, such as
temperature, light, water, minerals, and air.
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A Hierarchy of Interactions
• An organism’s habitat
– is the specific environment it lives in and
– includes the biotic and abiotic factors of its
surroundings.
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A Hierarchy of Interactions
• Ecology can be divided into four increasingly
comprehensive levels:
1. organismal ecology,
2. population ecology,
3. community ecology, and
4. ecosystem ecology.
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Figure 18.3
(a) Organismal ecology
(b) Population ecology (c) Community ecology
(d) Ecosystem ecology
A Hierarchy of Interactions
• An organism is an individual living thing.
• Organismal ecology is concerned with
evolutionary adaptations that enable individual
organisms to meet the challenges posed by their
abiotic environments.
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A Hierarchy of Interactions
• Population ecology
– addresses populations, groups of individuals of
the same species living in a particular geographic
area and
– concentrates mainly on factors that affect
– population density and
– growth.
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A Hierarchy of Interactions
• Community ecology
– is concerned with communities, all the organisms
that inhabit a particular area and
– focuses on how interactions between species
affect a community’s
– structure and
– organization.
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A Hierarchy of Interactions
• Ecosystem ecology
– is concerned with ecosystems, all the abiotic
factors in addition to the community of species in a
certain area and
– focuses on energy flow and the cycling of
chemicals among the various abiotic and biotic
factors.
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A Hierarchy of Interactions
• The biosphere is
– the global ecosystem,
– the sum of all the planet’s ecosystems, or
– all of life and where it lives.
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LIVING IN EARTH’S DIVERSE ENVIRONMENTS
• The distribution of life varies on a
– global scale and
– local scale.
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Figure 18.4
Abiotic Factors of the Biosphere
• Patterns in the distribution of life mainly reflect
differences in the abiotic factors of the
environment.
• In other words, the rocks and weather
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Energy Source
• All organisms require a usable source of energy to
live.
• Solar energy from sunlight
– is captured by chlorophyll during the process of
photosynthesis and
– powers most ecosystems.
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Figure 18.5
Energy Source
• Hydrothermal vents
– occur a mile or more below the ocean’s surface
and
– are ecosystems powered by chemoautotrophic
bacteria that derive energy from the oxidation of
inorganic chemicals such as hydrogen sulfide.
• Bacteria with similar metabolic talents support
communities of cave-dwelling organisms.
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Figure 18.6
Temperature
• Temperature affects metabolism.
– Few organisms can maintain a sufficiently active
metabolism at temperatures close to 0ºC.
– Temperatures above 45ºC destroy the enzymes of
most organisms.
• Most organisms function best within a specific
range of environmental temperatures.
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Figure 18.7
Water
• Water is essential to all life.
• For terrestrial organisms, the main water problem
is drying out.
• Aquatic organisms
– are surrounded by water and
– face problems of water balance if their own solute
concentration does not match that of their
surroundings.
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Figure 18.8
(a) Scales on a basilisk lizard
(b) Beaded water droplets
Figure 5.14
Animal cell
H2O
H2O
H2O
Normal
Lysing
Plant cell
H2O
H2O
Flaccid (wilts)
(a) Isotonic
solution
H2O
Turgid (normal)
(b) Hypotonic
solution
H2O
Shriveled
Plasma
membrane
Shriveled
(c) Hypertonic
solution
H2O
Inorganic Nutrients
• The distribution and abundance of plants are often
determined by the
– availability of inorganic nutrients such as nitrogen
and phosphorus and
– the structure, pH, and nutrient content of the soil.
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Inorganic Nutrients
• In many aquatic ecosystems, the growth of algae
and photosynthetic bacteria is often limited by
levels of
– nitrogen and
– phosphorus.
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Other Aquatic Factors
• Aquatic but not terrestrial ecosystems are more
limited by
– the levels of dissolved oxygen,
– salinity,
– currents, and
– tides.
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Other Terrestrial Factors
• Terrestrial but not aquatic ecosystems are more
limited by
– wind,
– storms, or
– fire.
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The Evolutionary Adaptations of Organisms
• The ability of organisms to live in Earth’s diverse
environments demonstrates the close relationship
between the fields of
– ecology and
– evolutionary biology.
• Evolutionary adaptation via natural selection
results from the interactions between
– organisms and
– their environments.
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Adjusting to Environmental Variability
• The abiotic factors in a habitat may vary
– from year to year,
– seasonally, or
– over the course of a day.
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Adjusting to Environmental Variability
• Birds may adjust to cold by
– migrating to warmer regions (a behavioral
response),
– growing heavier feathers (an anatomical
response), or
– fluffing up their feathers to trap more heat (a
physiological response).
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Figure 18.9
Adjusting to Environmental Variability
• These responses, which occur during the lifetime
of an individual, do not qualify as evolution, which
is change in a population over time.
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Physiological Responses
• Acclimation is
– gradual,
– reversible, and
– a physiological adjustment to an environmental
change.
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Physiological Responses
• The ability to acclimate is generally related to the
range of environmental conditions a species
naturally experiences.
• Among vertebrates,
– birds and mammals can tolerate the greatest
temperature extremes because they are
endotherms, while
– ectothermic reptiles can only tolerate a more
limited range of temperatures.
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Figure 18.10
Key
Number of lizard species
0
 1–5
 6–10
 11–15
 16–20
 20
Anatomical Responses
• Many organisms respond to environmental
challenges with some type of change in
– body shape and
– structure.
• Reversible change, such as a heavier fur coat in
response to cold, is an example of acclimation.
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Figure 18.11
Anatomical Responses
• Environmental variation can irreversibly affect
– growth and
– development.
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Figure 18.12
Behavioral Responses
• In contrast to plants, most animals can respond to
an unfavorable change in the environment by
moving to a new location.
– Ectotherms may shuttle between sun and shade.
– Migratory birds travel great distances in response
to changing seasons.
– Humans have an especially rich range of
behavioral responses.
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Figure 18.13
BIOMES
• A biome is
– a major terrestrial or aquatic life zone,
– characterized by
– vegetation type in terrestrial biomes or
– the physical environment in aquatic biomes.
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BIOMES
• Aquatic biomes
– occupy roughly 75% of Earth’s surface and
– are determined by their
– salinity and
– other physical factors.
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BIOMES
• Freshwater biomes
– have a salt concentration of less than 1% and
– include lakes, streams, rivers, and wetlands.
• Marine biomes
– typically have a salt concentration around 3% and
– include oceans, intertidal zones, coral reefs, and
estuaries.
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Freshwater Biomes
• Freshwater biomes
– cover less than 1% of Earth,
– contain a mere 0.01% of its water,
– harbor about 6% of all described species, and
– are used for
– drinking water,
– crop irrigation,
– sanitation, and
– industry.
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Freshwater Biomes
• Freshwater biomes fall into two broad groups:
1. standing water, which includes lakes and ponds,
and
2. flowing water, such as rivers and streams.
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Lakes and Ponds
• Standing bodies of water range from small ponds
to large lakes, such as North America’s Great
Lakes.
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Figure 18.14
Lakes and Ponds
• In lakes and large ponds, the communities of
plants, algae, and animals are distributed
according to the
– depth of water and
– distance from shore.
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Figure 18.15
Photic
zone
Benthic
realm
Aphotic
zone
Lakes and Ponds
• The photic zone, named because light is available
for photosynthesis, includes
– the shallow water near shore and
– the upper layer of water away from shore.
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Lakes and Ponds
• The aphotic zone
– is deeper and
– has light levels too low to support photosynthesis.
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Lakes and Ponds
• The benthic realm is
– at the bottom of all aquatic biomes,
– made up of sand and organic and inorganic
sediments, and
– occupied by communities of organisms that are
collectively called benthos.
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Lakes and Ponds
• The amount of phytoplankton growth in a lake or
pond is typically regulated by the nutrients
– nitrogen and
– phosphorus.
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Rivers and Streams
• Rivers and streams
– are bodies of water flowing in one direction and
– generally support quite different communities of
organisms than lakes and ponds.
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Figure 18.16
Rivers and Streams
• Near the source of a stream, the water is usually
– clear,
– cold,
– swift, and
– low in nutrients.
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Rivers and Streams
• Downstream, the water is usually
– murkier,
– warmer,
– slower, and
– higher in nutrients.
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Rivers and Streams
• Many streams and rivers have been affected by
pollution from human activities and dams to
– control floods,
– provide reservoirs for drinking water, or
– generate hydroelectric power.
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Figure 18.17
Dam
Canada
U.S.
Flathead
Lake N
MT
Seattle
WA
Portland
ID
OR
CA
NV
Wetlands
• A wetland is a transitional biome between
– an aquatic ecosystem and
– a terrestrial one.
• Wetlands
– support the growth of aquatic plants and
– are rich in species diversity.
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Figure 18.18
Marine Biomes
• Marine biomes are diverse, ranging from vivid coral
reefs to perpetually dark realms in the deepest
regions.
• As in freshwater biomes, the seafloor is known as
the benthic realm.
• The pelagic realm includes all of the open water
of the oceans.
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Figure 18.19
High
tide
Low
tide
Pelagic realm
Sea
star
Oarweed
Man-of-war
Turtle
Brain coral
Phytoplankton Zooplankton
Intertidal
zone
Continental shelf
Blue shark
200 m
Sponges
Sperm whale
Sea pen
Hatchet fish
Octopus
Benthic realm
Photic
zone
Sea spider
Rat-tail fish
Brittle star
Gulper
eel
Anglerfish
Glass
sponge
Sea
cucumber
Tripod
fish
“Twilight”
Aphotic
zone
1,000 m
No light
6,000–
10,000 m
Marine Biomes
• In shallow areas such as the submerged parts of
continents, called continental shelves, the photic
zone includes pelagic and benthic regions.
• In these sunlit areas, photosynthesis by
phytoplankton and multicellular algae provides
energy for a diverse community of animals.
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Marine Biomes
• The pelagic photic zone includes
– zooplankton (free-floating animals, including many
microscopic ones),
– fishes, and
– marine mammals.
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Marine Biomes
• The coral reef biome occurs
– in the photic zone of warm tropical waters,
– in scattered locations around the globe.
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Figure 18.20
Marine Biomes
• The photic zone extends down a maximum of
200 m in the ocean.
• The region between 200 and 1,000 m is
– dimly lit, sometimes called the twilight zone, and
– dominated by a fascinating variety of small fish and
crustaceans.
• Below 1,000 m, the ocean is completely dark.
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Marine Biomes
• The intertidal zone is where
– the ocean meets land,
– the shore is pounded by waves during high tide,
and
– the bottom is exposed to the sun and drying winds
during low tide.
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Figure 18.21
Marine Biomes
• Estuaries
– are a transition area between a river and the
ocean,
– have a saltiness ranging from nearly that of fresh
water to that of the ocean, and
– are among the most productive areas on Earth.
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Figure 18.22
Marine Biomes
• Estuaries are threatened by
– landfills,
– nutrient pollution,
– contamination by pathogens or toxic chemicals,
such as the massive Deepwater Horizon oil spill in
the Gulf of Mexico in 2010, and
– alteration of freshwater inflow.
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How Climate Affects Terrestrial Biome Distribution
• Terrestrial biomes are primarily determined by
climate, especially
– temperature and
– rainfall.
• Earth’s global climate patterns are largely the
result of
– the input of radiant energy from the sun and
– the planet’s movement in space.
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Figure 18.23
Arctic Circle
Low angle of
incoming sunlight
60º N
30º N
Tropic of
Cancer
Sunlight strikes
most directly
0º (equator)
Tropic of
Capricorn
30º S
Low angle of
incoming sunlight
60º S
Atmosphere
Antarctic Circle
How Climate Affects Terrestrial Biome Distribution
• Heated by the direct rays of the sun, air at the
equator
– rises,
– then cools, forming clouds, and
– drops rain.
• This largely explains why rain forests are
concentrated in the tropics, the region from the
Tropic of Cancer to the Tropic of Capricorn.
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Figure 18.24
Descending
dry air
absorbs
moisture
Ascending
moist air
Trade winds releases Trade winds
moisture
Descending
dry air
absorbs
moisture
Doldrums
0º
Temperate
zone
Tropics
Temperate
zone
How Climate Affects Terrestrial Biome Distribution
• Temperate zones generally have milder climates
than the tropics or the polar regions. They occur in
latitudes between
– the tropics and the Arctic Circle in the north and
– the tropics and the Antarctic Circle in the south.
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How Climate Affects Terrestrial Biome Distribution
• Climate is also affected by
– proximity to large bodies of water and
– the presence of landforms such as mountain
ranges.
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How Climate Affects Terrestrial Biome Distribution
• Mountains affect climate in two major ways.
– First, air temperature drops as elevation increases.
– This results in several biomes moving up a tall
mountain.
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Figure 18.25
Spruce-fir forest
10,000
Pine woodland
8,000
Oak woodland
7,000
6,000
Desert grassland
5,000
4,000
Desert
3,000
Elevation (ft)
9,000
How Climate Affects Terrestrial Biome Distribution
– Second, mountains can
– block the flow of cool, moist air from a coast and
– cause radically different climates on opposite
sides of a mountain range.
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Figure 18.26
Wind
direction
Pacific
Ocean
Coast
Range
East
Sierra
Nevada
Rain shadow
Desert
Terrestrial Biomes
• Terrestrial ecosystems are grouped into biomes
primarily on the basis of their vegetation type.
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Figure 18.27
30º N
Tropic of
Cancer
Equator
Tropic of Capricorn
30º S
Key
Tropical forest
Savanna
Desert
Chaparral
Temperate grassland
Temperate broadleaf forest
Coniferous forest
Arctic tundra
High mountains (coniferous forest and
alpine tundra)
Polar ice
Terrestrial Biomes
• A climograph is a visual representation of the
differences in
– precipitation and
– temperature ranges that characterize terrestrial
biomes.
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Annual mean temperature (ºC)
Figure 18.28
30
15
0
−15
100
0
200
300
400
Annual mean precipitation (cm)
Key
Tropical forest
Temperate broadleaf forest
Desert
Coniferous forest
Temperate grassland
Tundra
Tropical Forest
• Tropical forests occur in equatorial areas, where
– the temperature is warm, and
– days are 11–12 hours long year-round.
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Tropical Rainforest
Precipitation
Temperature
range
Figure 18.29
Savanna
• Savannas
– are dominated by grasses and scattered trees,
– are warm year-round, and
– experience rainfall of 30–50 cm (roughly 12–20
inches per year) with dramatic seasonal variation.
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Savanna
Fire
Precipitation
Temperature
range
Figure 18.30
Figure 18.30a
Desert
• Deserts
– are the driest of all biomes,
– are characterized by low and unpredictable rainfall
of less than 30 cm (about 12 inches) a year, and
– may be very hot or very cold.
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Desert
Precipitation
Temperature
range
Figure 18.31
Chaparral
• Chaparral has a climate that results from cool
ocean currents circulating offshore and producing
– mild, rainy winters and
– hot, dry summers.
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Chaparral
Fire
Precipitation
Temperature
range
Figure 18.32
Temperate Grassland
• Temperate grasslands
– are mostly treeless,
– have 25–75 cm (10–30 inches) of rain per year,
– experience frequent droughts and fires, and
– are characterized by grazers including bison and
pronghorn in North America.
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Temperate grassland
Fire
Precipitation
Temperature
range
Figure 18.33
Temperate Broadleaf Forest
• Temperate broadleaf forest
– occurs throughout midlatitudes where there
is sufficient moisture to support the growth
of large trees, ranging from 75 to 150 cm
(30 to 60 inches), and
– includes dense stands of deciduous trees in the
Northern Hemisphere.
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Temperate Broadleaf Forest
• Deciduous trees drop their leaves before winter,
when
– temperatures are too low for effective
photosynthesis and
– water lost by evaporation is not easily replaced
from frozen soil.
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Temperate broadleaf forest
Precipitation
Temperature
range
Figure 18.34
Coniferous Forest
• Coniferous forests
– are dominated by cone-bearing evergreen trees
and
– include the northern coniferous forest, or taiga, the
largest terrestrial biome on Earth.
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Coniferous forest
Precipitation
Temperature
range
Figure 18.35
Coniferous Forest
• Temperate rain forests
– are found along coastal North America from Alaska
to Oregon and
– are also coniferous forests.
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Tundra
• Tundra
– covers expansive areas of the Arctic between the
taiga and polar ice and
– is characterized by
– permafrost (permanently frozen subsoil),
– bitterly cold temperatures, and
– high winds.
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Tundra
Precipitation
Temperature
range
Figure 18.36
Polar Ice
• Polar ice covers the land
– at high latitudes north of the arctic tundra in the
Northern Hemisphere and
– in Antarctica in the Southern Hemisphere.
• Only a small portion of these landmasses is free of
ice or snow, even during the summer.
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Polar Ice
Precipitation
Temperature
range
Figure 18.37
The Water Cycle
• All parts of the biosphere are linked by the global
water cycle.
• Human activities that affect the global water cycle
include
– destruction of forests and
– pumping large amounts of groundwater to the
surface for irrigation.
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Figure 18.38
Solar
heat
Water vapor
Net
movement of
water vapor
Water vapor
Precipitation
Precipitation
Evaporation
Evaporation
and
transpiration
Oceans
Flow of
water from
land to sea
Surface
water and
groundwater
Human Impact on Biomes
• Sustainability is the goal of developing,
managing, and conserving Earth’s resources in
ways that meet the needs of people today without
compromising the ability of future generations to
meet their needs.
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Forests
• Satellite photos of a small area in Brazil show how
thoroughly a landscape can be altered in a short
amount of time.
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Figure 18.39
In 1975, the forest in this remote
region was virtually intact.
Same area in 2001, after a paved
highway through the region.
Forests
• Every year, more and more forested land is
cleared for agriculture.
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Figure 18.40
Fresh Water
• The impact of human activities on freshwater
ecosystems may pose an even greater threat to life
on Earth, including ourselves, than the damage to
terrestrial ecosystems.
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Fresh Water
• Las Vegas, the population center of Clark County,
Nevada, is one example of a city whose water
resources are increasingly stressed by drought and
overuse.
• The water level in Lake Mead has
– dropped drastically and
– parched cities and farms farther downstream,
which are pleading for more water.
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Figure 18.41
(a) May 1973
(b) May 2000
Figure 18.42
GLOBAL CLIMATE CHANGE
• Global climate patterns are changing because of
rising concentration in the atmosphere of
– carbon dioxide (CO2) and
– certain other gases.
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The Greenhouse Effect and Global Warming
• Greenhouse gases
– include CO2, water vapor, and methane,
– are transparent to solar radiation,
– absorb or reflect heat, and
– contribute to increases in global temperatures in
what is often called the greenhouse effect.
Blast Animation: The Greenhouse Effect
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Figure 18.43a
Some heat
energy escapes
into space
Sunlight
Atmosphere
Radiant heat
trapped by
greenhouse
gases
Figure 18.43b
The Greenhouse Effect and Global Warming
• The largest increases are in
– the northernmost regions of the Northern
Hemisphere and
– parts of Antarctica.
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Figure 18.44
Antarctic
Peninsula
−4.1
−4
−2
−1
−0.5
−0.2
0.2
0.5
1
2
4
4.1
The Accumulation of Greenhouse Gases
• The vast majority of scientists are confident that
human activities have caused the rising
concentrations of greenhouse gases.
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Figure 18.45
Carbon dioxide (CO2) (ppm)
400
350
300
250
0
500
1000
Year
1500
2000
The Accumulation of Greenhouse Gases
• Overall, the uptake of CO2 by photosynthesis
roughly equals the release of CO2 by cellular
respiration.
• However,
– extensive deforestation has significantly decreased
the incorporation of CO2 into organic material and
– CO2 is flooding into the atmosphere from the
burning of fossil fuels and wood.
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Figure 18.46
Atmosphere
Photosynthesis
Respiration
Combustion of
fossil fuels
Ocean
The Process of Science: How Does Climate Change
Affect Species Distribution?
• Observations:
– The average temperature in Europe has risen
0.8ºC.
– Butterflies are sensitive to temperature change.
• Question: Have the ranges of butterflies changed
in response to the temperature changes?
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The Process of Science: How Does Climate Change
Affect Species Distribution?
• Hypothesis: Butterfly range boundaries are
shifting in line with the warming trend.
• Prediction:
– Butterfly species will establish new populations to
the north of their former ranges.
– Butterfly populations at the southern edges of their
ranges will become extinct.
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The Process of Science: How Does Climate Change
Affect Species Distribution?
• Experiment: Historical data on the ranges of 35
species of butterflies in Europe were analyzed.
• Results:
– More than 60% of the species have pushed their
northern range boundaries poleward over the last
century, some by as much as 150 miles.
– The southern boundaries have simultaneously
contracted for some species, but not for others.
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Figure 18.47
Finland
Sweden
Norway
Estonia
Russia
Latvia
Denmark
Lithuania
Europe
Africa
Argynnis paphia (silver-washed fritillary butterfly)
Figure 18.47a
Europe
Africa
Figure 18.47b
Finland
Sweden
Norway
Estonia
Denmark
Latvia
Lithuania
Russia
Figure 18.47c
Argynnis paphia (silver-washed fritillary butterfly)
Effects of Climate Change on Ecosystems
• In many plants and animals, life cycle events are
triggered by
– warming temperatures or
– day length.
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Effects of Climate Change on Ecosystems
• As global temperatures warm, and day length
remains steady, natural interactions may become
out of sync.
– The winter white fur of snowshoe hares may be
conspicuous against a greening landscape.
– Plants may bloom before pollinators have
emerged.
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Effects of Climate Change on Ecosystems
• The combined effects of climate change on forest
ecosystems in western North America have
spawned catastrophic wildfire seasons.
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Figure 18.48
Effects of Climate Change on Ecosystems
• Warmer weather helps bark beetles
– bore into drought-stressed conifers and
– reproduce twice a year instead of just once.
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Figure 18.49
Looking to Our Future
• Emissions of greenhouse gases continue to rise.
• In the United States, for example, total emissions
increased more than 13% from 1990 to 2008.
• At this rate, further climate change is inevitable.
© 2013 Pearson Education, Inc.
Looking to Our Future
• The amount of greenhouse gas emitted as the
result of the actions of a single individual is that
person’s carbon footprint.
• We can reduce our carbon footprints by
– reducing our use of electricity,
– driving less, and
– recycling.
© 2013 Pearson Education, Inc.
Figure 18.50
Looking to Our Future
• In addition, eating locally grown fresh foods may
lower the greenhouse gas emissions that result
from food processing and transportation.
© 2013 Pearson Education, Inc.
Figure 18.51
Evolution Connection:
Climate Change as an Agent of Natural Selection
• Can evolutionary adaptations counteract the
negative effects of climate change on organisms?
• The species most likely to adapt have
– high genetic variability and
– short life spans.
© 2013 Pearson Education, Inc.
Figure 18.52
(a) Pitcher plant mosquito
(b) Adélie penguin
Figure 18.UN01
Organismal
ecology
Population
ecology
Community
ecology
Ecosystem ecology
Mean annual temperature (ºC)
Figure 18.UN02
30
a.
b.
c.
d.
15
e.
0
f.
15
100
200
300
Mean annual precipitation (cm)
400