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Chapter 54
Ecosystems
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Ecosystems, Energy, and Matter
• An ecosystem consists of all the organisms living
in a community, as well as the abiotic factors with
which they interact
• Ecosystems range from a microcosm, such as an
aquarium, to a large area such as a lake or forest
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Regardless of an ecosystem’s size, its dynamics
involve two main processes: energy flow and
chemical cycling
• Energy flows through ecosystems while matter
cycles within them
• Energy flows through an ecosystem, entering as
light and exiting as heat
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Energy is conserved but degraded to heat
during ecosystem processes
Tertiary
consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
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Sun
Decomposition
• Decomposition connects all trophic levels
• Detritivores, mainly bacteria and fungi, recycle
essential chemical elements by decomposing
organic material and returning elements to
inorganic reservoirs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 54.2: Physical and chemical factors limit
primary production in ecosystems
• Primary production in an ecosystem is the
amount of light energy converted to chemical
energy by autotrophs during a given time period
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Gross and Net Primary Production
• Total primary production is known as the
ecosystem’s gross primary production (GPP)
• Net primary production (NPP) is GPP minus
energy used by primary producers for respiration
• Only NPP is available to consumers
• Ecosystems vary greatly in net primary production
and contribution to the total NPP on Earth
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LE 54-4
Open ocean
Continental shelf
Estuary
Algal beds and reefs
Upwelling zones
Extreme desert, rock, sand, ice
Desert and semidesert scrub
Tropical rain forest
Savanna
Cultivated land
Boreal forest (taiga)
Temperate grassland
Woodland and shrubland
Tundra
Tropical seasonal forest
Temperate deciduous forest
Temperate evergreen forest
Swamp and marsh
Lake and stream
5.2
0.3
0.1
0.1
4.7
3.5
3.3
2.9
2.7
2.4
1.8
1.7
1.6
1.5
1.3
1.0
0.4
0.4
0
Key
Marine
Terrestrial
125
360
65.0
10 20 30 40 50 60
Percentage of Earth’s
surface area
Freshwater (on continents)
24.4
5.6
1,500
2,500
1.2
0.9
0.1
0.04
0.9
500
3.0
90
22
2,200
7.9
9.1
9.6
5.4
3.5
900
600
800
600
700
140
0.6
7.1
4.9
3.8
2.3
0.3
1,600
1,200
1,300
2,000
250
0
500 1,000 1,500 2,000 2,500
Average net primary
production (g/m2/yr)
0
10 15 20 25
5
Percentage of Earth’s net
primary production
• Overall, terrestrial ecosystems contribute about
two-thirds of global NPP
• Marine ecosystems contribute about one-third
North Pole
60°N
30°N
Equator
30°S
60°S
South Pole
120°W
180°
60°W
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Pearson Education, Inc.
publishing as Benjamin
Cummings
0°
60°E
120°E
180°
Primary Production in Marine and Freshwater
Ecosystems
• In marine and freshwater ecosystems, both
light and nutrients control primary production
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Light Limitation
• Depth of light penetration affects primary
production in the photic zone of an ocean or lake
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A limiting nutrient is the element that must be
added for production to increase in an area
• Nitrogen and phosphorous are typically the
nutrients that most often limit marine production
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Video: Cyanobacteria (Oscillatoria)
• The addition of large amounts of nutrients to lakes
has a wide range of ecological impacts
• In some areas, sewage runoff has caused
eutrophication of lakes, which can lead to loss of
most fish species
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Primary Production in Terrestrial and Wetland
Ecosystems
• Climatic factors such as temperature and
moisture affect primary production
• Actual evapotranspiration is the water
annually transpired by plants and evaporated
from a landscape
• It is related to net primary production
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 54-8
Net primary production (g/m2/yr)
3,000
Tropical forest
2,000
Temperate forest
1,000
Mountain coniferous forest
Desert
shrubland
Temperate grassland
Arctic tundra
0
0
1,500
500
1,000
Actual evapotranspiration (mm/yr)
Concept 54.3: Energy transfer between trophic
levels is usually less than 20% efficient
• Secondary
production of an
ecosystem is the
amount of chemical
energy in food
converted to new
biomass during a
given period of time
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Growth (new biomass)
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Cellular
respiration
Trophic Efficiency and Ecological Pyramids
• Trophic efficiency is the percentage of
production transferred from one trophic level to the
next
• It usually ranges from 5% to 20%
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 54-11
Tertiary
consumers
Secondary
consumers
Primary
consumers
Primary
producers
10 J
100 J
1,000 J
10,000 J
1,000,000 J of sunlight
Pyramids of Biomass
• In a biomass pyramid, each tier represents the
dry weight of all organisms in one trophic level
Trophic level
Tertiary consumers
Dry weight
(g/m2)
1.5
Secondary consumers
11
Primary consumers
37
Primary producers
809
Most biomass pyramids show a sharp decrease in biomass at
successively higher trophic levels, as illustrated by data from a
bog at Silver Springs, Florida.
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• Certain aquatic ecosystems have inverted
biomass pyramids: Primary consumers outweigh
the producers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pyramids of Numbers
• A pyramid of numbers represents the number of
individual organisms in each trophic level
Trophic level
Tertiary consumers
Number of
individual organisms
3
Secondary consumers
354,904
Primary consumers
708,624
Primary producers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5,842,424
• Dynamics of energy flow in ecosystems have
important implications for the human population
• Eating meat is a relatively inefficient way of
tapping photosynthetic production
Trophic level
Secondary
consumers
Primary
consumers
Primary
producers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 54-16
All elements
cycle between
organic and
inorganic
reservoirs
Reservoir a
Reservoir b
Organic
materials
available
as nutrients
Organic
materials
unavailable
as nutrients
Fossilization
Living
orgusanisms,
detrit
Assimilation,
photosynthesis
Coal, oil,
peat
Respiration,
decomposition,
excretion
Burning
of fossil fuels
Reservoir c
Reservoir d
Inorganic
materials
available
as nutrients
Inorganic
materials
unavailable
as nutrients
Atmosphere,
soil, water
Weathering,
erosion
Formation of
sedimentary rock
Minerals
in rocks
LE 54-17a
Transport
over land
Solar energy
Net movement of
water vapor by wind
Precipitation
over ocean
Evaporation
from ocean
Precipitation
over land
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
LE 54-17b
CO2 in atmosphere
Photosynthesis
Cellular
respiration
Burning of
fossil fuels
and wood
Higher-level
Primary consumers
consumers
Carbon compounds
in water
Detritus
Decomposition
LE 54-17c
N2 in atmosphere
Assimilation
Nitrogen-fixing
bacteria in root
nodules of legumes Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
NO3–
Nitrifying
bacteria
Nitrification
NO2–
NH4+
Nitrifying
bacteria
Denitrifying
bacteria
LE 54-17d
Rain
Geologic
uplift
Weathering
of rocks
Plants
Runoff
Consumption
Sedimentation
Soil
Leaching
Plant uptake
of PO43–
Decomposition
Decomposition and Nutrient Cycling Rates
• Decomposers (detritivores) play a key role in the
general pattern of chemical cycling
• Rates at which nutrients cycle in different
ecosystems vary greatly, mostly as a result of
differing rates of decomposition
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 54-18
Consumers
Producers
Decomposers
Nutrients
available
to producers
Abiotic
reservoir
Geologic
processes
Acid Precipitation
• Combustion of fossil fuels is the main cause of
acid precipitation
• North American and European ecosystems
downwind from industrial regions have been
damaged by rain and snow containing nitric and
sulfuric acid
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 54-21
4.6
4.3
4.6
4.3
4.6
4.1
4.3
4.6
Europe
North America
LE 54-22
5.0
5.3
5.4
5.2
5.5
5.2
5.5
5.6
5.4
5.2
5.3
5.3
5.5
6.0
5.9 5.5
5.3
5.2
5.3
5.4
5.4
5.3 5.0
5.05.1 4.9 5.4
5.1
6.3
5.7
5.6
4.9
5.4
5.3
5.0
5.2
5.4
5.1
5.5
5.2 4.8
5.3
4.5 4.6 4.7
5.4
5.2 5.15.0
4.8
4.7
5.2
4.5 4.6
4.8
4.3 4.5 4.5
5.2 4.9
5.5
4.5
5.6
4.5 4.5 4.6
4.9 4.7
4.7
4.3 4.4
4.5
4.6
5.1 4.7
4.6
4.5
4.7
5.4
4.5
4.1 4.4
5.3
5.3
4.4 4.4
4.6 4.8
4.3
4.6
4.6
4.6 4.5
4.4
4.5
4.7
4.5
4.5 4.5
4.7
4.7
4.6
4.8
4.6
5.4
4.6
4.8 4.6
4.5
5.0
4.5 4.5
4.7
4.8
4.9
4.5
4.6
4.5
Field pH
4.7
4.5
5.0
4.7
4.8 4.7 4.7
5.0
4.8 5.1 4.7
5.3
4.7
4.7
5.2–5.3
5.0
5.4
4.7 4.6
4.7
4.9
5.1–5.2
4.8
4.7
4.8
5.3
4.8
4.9
5.0–5.1
4.8
4.7
4.9–5.0
4.9
4.8
4.7
5.6
6.1
5.2
5.3
5.3
5.2
5.7
5.0 5.0
5.1
5.1
5.7
5.1
5.0
5.0
4.8
4.7
4.7
4.7
4.9
4.8–4.9
4.7–4.8
4.6–4.7
4.5–4.6
4.4–4.5
4.3–4.4
<4.3
Toxins in the Environment
• In biological
magnification, toxins
concentrate at higher
trophic levels, where
biomass is lower
Herring
gull eggs
124 ppm
Concentration of PCBs
• One reason toxins are
harmful is that they
become more
concentrated in
successive trophic
levels
Lake trout
4.83 ppm
Smelt
1.04 ppm
Zooplankton
0.123 ppm
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Phytoplankton
0.025 ppm