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Chapter 18
An Introduction to Ecology
and the Biosphere
PowerPoint® Lectures for
Campbell Essential Biology, Fourth Edition
– Eric Simon, Jane Reece, and Jean Dickey
Campbell Essential Biology with Physiology, Third Edition
– Eric Simon, Jane Reece, and Jean Dickey
Lectures by Chris C. Romero, updated by Edward J. Zalisko
© 2010 Pearson Education, Inc.
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.
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AN OVERVIEW OF ECOLOGY
• Ecology is the scientific study of the interactions between
organisms and their environments.
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• 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
– Recording its structure and processes
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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
–
The living component of the environment
– Abiotic factors
–
Are the environment’s nonliving component
–
Include chemical and physical factors, such as temperature, light,
water, minerals, and air
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• 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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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
– Powers most ecosystems
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Chlorophyll levels around the world.
GREEN = HIGH LEVELS
DARKER COLORS = LOW LEVELS
Figure 18.5
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.
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Water
• Water is essential to all life.
• For terrestrial organisms, the main water problem is drying out.
• Aquatic organisms
– Are surrounded by water
– Face problems of water balance if their own solute concentration does not
match that of their surroundings
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Animal cell
H2O
H2O
H 2O
Normal
Lysing
H 2O
Flaccid (wilts)
(a) Isotonic
solution
Shriveled
Plasma
membrane
Plant cell
H 2O
H2O
H 2O
Turgid
(b) Hypotonic
solution
H 2O
Shriveled
(c) Hypertonic
solution
Figure 5.14
Nutrients
• The distribution and abundance of plants is often determined by
the
– Availability of nitrogen and phosphorus
– The structure, pH, and nutrient content of the soil
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Other Aquatic Factors
• Aquatic but not terrestrial ecosystems are more limited by
– The levels of dissolved oxygen and salinity
– Currents
– Tides
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Other Terrestrial Factors
• Terrestrial but not aquatic ecosystems are more limited by
– Wind
– Storms
– Fire
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Key
Number of lizard species
=0
= 1–5
= 6–10
= 11–15
= 16–20
= 20+
Figure 18.10
Anatomical Responses
• Many organisms respond to environmental challenges with some
type of change in
– Body shape
– 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
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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BIOMES
• A biome is
– A major terrestrial or aquatic life zone
– Characterized by
–
Vegetation type in terrestrial biomes
–
The physical environment in aquatic biomes
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• Aquatic biomes
– Occupy roughly 75% of Earth’s surface
– Are determined by their
–
Salinity (what is the salinity of the worlds oceans?)
–
Other physical factors
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• Freshwater biomes
– Typically have a salt concentration of less than 1%
– Include lakes, streams, rivers, and wetlands
• Marine biomes
– Typically have a salt concentration around 3%
– 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
– Are used for drinking water, crop irrigation, sanitation, and industry
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Photic
zone
Benthic
realm
Aphotic
zone
Figure 18.15
Wetlands
• A wetland is a transitional biome between an aquatic ecosystem
and a terrestrial one.
• Wetlands
– Support the growth of aquatic plants
– Are among the richest of biomes in terms of 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.
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High tide
Low tide
Pelagic realm (open water)
Sea star
(to 33 cm)
Oarweed (to 2 m)
Brain coral
(to 1.8 m) PhytoZooplankton plankton
Intertidal Continental
zone
shelf
Sponges
(1 cm–1 m)
Turtle
(60–180 cm)
Blue shark (to 2 m)
Photic
zone
200 m
Sperm whale
(10–20 cm)
Sea pen
(to 45 cm)
Benthic realm
(seafloor from continental
shelf to deep-sea bottom)
Man-of-war
(to 50 m long)
Octopus
(to 10 m)
Sea spider
(1–90 cm)
Brittle
star
(to 60 cm) Glass
Rat-tail fish
(to 80 cm)
Hatchet fish
(2–60 cm)
Gulper eel
(to 180 cm)
Anglerfish
(45 cm–2 m)
sponge Sea cucumber Tripod fish
(to 30 cm)
(to 1.8 m)
(to 40 cm)
“Twilight”
Aphotic
zone
1,000–
4,000 m
No light
6,000–
10,000 m
Figure 18.19
• 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
– Are among the most productive areas on Earth
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Figure 18.22
• Estuaries are threatened by
– Landfills
– Nutrient pollution
– Contamination by pathogens or toxic chemicals
– Alteration of freshwater inflow
– The introduction of non-native species
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How Climate Affects Terrestrial Biome
Distribution
• Terrestrial biomes are primarily determined by
– Temperature
– Rainfall
• Earth’s global climate patterns are largely the result of
– The input of radiant energy from the sun
– The planet’s movement in space
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North Pole
60º N
Low angle of
incoming sunlight
30º N
Tropic of
Cancer
Sunlight strikes
most directly
0º (equator)
Tropic of
Capricorn
30º S
Low angle of
incoming sunlight
Atmosphere
60º S
South Pole
Figure 18.23
• 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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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
Figure 18.24
• Climate is also affected by
– Proximity to large bodies of water
– The presence of landforms such as mountain ranges
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Terrestrial Biomes
• Terrestrial ecosystems are grouped into biomes primarily on the
basis of their vegetation type.
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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
Figure 18.27
Desert
• Deserts
– Are the driest of all biomes
– May be very hot or very cold
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Figure 18.31
Precipitation
Temperature
Descending
dry air
absorbs
moisture
Ascending
moist air
Trade winds releases Trade winds
moisture
Descending
dry air
absorbs
moisture
Doldrums
0º
Temperate
zone
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Tropics
Temperate
zone
Figure 18.24
Temperate Broadleaf Forest
• Temperate broadleaf forest
– Occurs throughout midlatitudes where there is sufficient moisture to
support the growth of large trees
– Includes dense stands of deciduous trees in the Northern Hemisphere
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Figure 18.34
Precipitation
Temperature
Coniferous Forest
• Coniferous forests
– Are dominated by cone-bearing evergreen trees
– Include the northern coniferous forest, or taiga, the largest terrestrial
biome on Earth
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Figure 18.35
Precipitation
Temperature
Polar Ice
• Polar ice covers the land at high latitudes north of the arctic
tundra in the northern hemisphere and Antarctica in the southern
hemisphere.
• Only a small portion of these land masses is free of ice or snow,
even during the summer.
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Figure 18.37
Precipitation
Temperature
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
– Pumping large amounts of groundwater to the surface for irrigation
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Solar
heat
Water vapor
over the sea
Precipitation
over the sea
Net movement
of water vapor
by wind
Evaporation
from the sea
Water vapor
over the land
Precipitation
over the land
Evaporation
and
transpiration
Oceans
Flow of water
from land to sea
Surface water
and groundwater
Figure 18.38
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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Satellite photos of a small area in Brazil show how thoroughly
a landscape can be altered in a short amount of time.
1975
2001
Figure 18.39
Every year, more and more forested land is cleared for
agriculture.
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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GLOBAL CLIMATE CHANGE
• Global climate patterns are changing because of rising
concentration in the atmosphere of
– Carbon dioxide (CO2)
– Some 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
– Contribute to increases in global temperatures
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Some heat
energy escapes
into space
Sunlight
Atmosphere
Radiant heat
trapped by
greenhouse gases
Figure 18.43
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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Carbon dioxide (CO2) (ppm)
400
350
300
250
0
500
1000
1500
2000
Year
Figure 18.45
• Overall, the uptake of CO2 by photosynthesis roughly equals the
release of CO2 by cellular respiration.
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Atmosphere
Photosynthesis
Respiration
Combustion
of fossil fuel
Ocean
Figure 18.46
Effects of Climate Change on Ecosystems
• In many plants and animals, life cycle events are triggered by
– Warming temperatures
– Day length
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• As global temperatures warm, and day length remains steady,
natural interactions may become out of sync.
– Plants may bloom before pollinators have emerged.
– Eggs may hatch before dependable food sources are available.
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Looking to Our Future
• Emissions of greenhouse gases are accelerating.
• From 2000–2005 global CO2 emissions increased four times
faster than in the preceding 10-year span.
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• 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 energy
– Driving less
– Recycling
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• In addition, eating locally grown fresh foods may lower the
greenhouse gas emissions that result from food processing and
transportation.
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