Chapter 55
Ecosystems
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: Observing Ecosystems
• An ecosystem consists of all the organisms living
in a community, as well as the abiotic components
with which they interact
• Ecosystems range from a microcosm, such as a
roach stomach, to a large area such as a lake or
forest
• Regardless of an ecosystem’s size, its dynamics
involve two main processes: energy flow and
chemical cycling
• Therefore, ecologists study the transformations
of energy and matter within ecosystem 2
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Conservation of Energy and Mass (matter)
• Energy enters an ecosystem as solar radiation,
is conserved, and is lost from organisms as
heat
• The law of conservation of mass states that
matter cannot be created or destroyed
• Chemical elements are continually recycled
within ecosystems
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Energy, Mass, and Trophic Levels
• Autotrophs build molecules themselves using
photosynthesis or chemosynthesis
heterotrophs depend on the biosynthetic output
of other organisms
• Energy and nutrients pass from primary
producers (autotrophs) to primary
consumers (herbivores) to secondary
consumers (carnivores) to tertiary
consumers (carnivores that feed on other
carnivores)
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• Detritivores, or decomposers, are consumers
that derive their energy from detritus, nonliving
organic matter
• Decomposition connects all trophic
levels
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-3
Fig. 55-4
Tertiary consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Sun
Concept 55.2: Energy and other limiting factors
control 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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Fig. 55-6
Net primary production (kg carbon/m2·yr)
·
0
1
2
3
Fig. 55-8
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
500
1,500
1,000
Actual evapotranspiration (mm H2O/yr)
Concept 55.3: Energy transfer between trophic
levels is typically only 10% efficient
• Secondary production of an ecosystem is the
amount of chemical energy in food converted
to new biomass during a given period of time
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Fig. 55-9
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
Cellular
respiration
33 J
Growth (new biomass)
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%
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Fig. 55-10
Tertiary
consumers
Secondary
consumers
10 J
100 J
Primary
consumers
1,000 J
Primary
producers
10,000 J
Approximately
0.1% of chemical
energy fixed by
photosynthesis
reaches a tertiary
consumer
1,000,000 J of sunlight
Concept 55.4: Biological and geochemical processes
cycle nutrients between organic and inorganic parts
of an ecosystem
• Life depends on recycling chemical elements
• Nutrient circuits in ecosystems involve biotic
and abiotic components and are often called
biogeochemical cycles
• The most important parts of biogeochemical
cycles are:
- Water cycle
- Carbon cycle
- Nitrogen cycle
- Phosphorous cycle
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Thank you for
your attention
and
participation!
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
You should now be able to:
1. Define and compare primary production,
secondary production, and trophic efficiency
2. Explain energy flow and nutrients cycle within
an ecosystem
3. Distinguish between primary and secondary
production
4. List four major biogeochemical cycles on the
Earth
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings