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Ch. 55 Warm-Up 1. Draw an energy pyramid and
label the following trophic levels:
▫ Primary producer
▫ Primary consumer
▫ Secondary consumer
▫ Tertiary consumer
2. What is an example of an
organism at each level of the
pyramid in #1?
3. If 5000 J of energy is available in
producers, how much of that
energy would be available to
tertiary consumers?
Define Ch. 55 Terms:
Autotroph
Heterotroph
Detritivore
Gross primary
production (GPP)
Net primary production
(NPP)
Biogeochemical cycle
Nitrogen fixation
Chapter 55: Ecosystems
You Must Know:
• How energy flows through the ecosystem (food
chains and food webs)
• The difference between gross primary
productivity and net primary productivity.
• The carbon and nitrogen biogeochemical cycles.
Ecosystems
Ecosystem = sum of all the organisms living
within its boundaries (biotic community) + abiotic
factors with which they interact
Involves two unique processes:
1. Energy flow
2. Chemical cycling
Overview of energy & nutrient dynamics
Energy Flow in an Ecosystem
• Energy cannot be recycled must be constantly
supplied to an ecosystem (mostly by SUN)
• The autotrophs (“self feeders”) are the primary
producers, and are usually photosynthetic (plants
or algae).
▫ They use light energy to synthesize sugars and other
organic compounds.
• Heterotrophs (“other feeders”) – can’t make own
food
• Heterotrophs are
at trophic levels
above the primary
producers and
depend on their
photosynthetic
output.
▫ Herbivores that eat primary producers are
called primary consumers.
▫ Carnivores that eat herbivores are called
secondary consumers.
▫ Carnivores that eat secondary consumers are
called tertiary consumers.
▫ Another important group of heterotrophs is the
detritivores, or decomposers.
They get energy from detritus, nonliving
organic material, and play an important role
in material cycling.
Main decomposers:
fungi & prokaryotes
Primary Production
• Primary production = amt. of light energy that
is converted to chemical energy
• Gross primary production (GPP): total primary
production in an ecosystem
• Net primary production (NPP) = gross primary
production minus the energy used by the
primary producers for respiration (R):
▫ NPP = GPP – R
• NPP = storage of chemical energy available to
consumers in an ecosystem
Open ocean
Continental shelf
Upwelling zones
Extreme desert, rock, sand, ice
Swamp and marsh
Lake and stream
Desert and semidesert scrub
Tropical rain forest
Temperate deciduous forest
Temperate evergreen forest
Tropical seasonal forest
Savanna
Cultivated land
Estuary
Algal beds and reefs
Boreal forest (taiga)
Temperate grassland
Woodland and shrubland
Tundra
0.4
0.4
1.0
1.3
1.5
1.6
1.7
1.8
2.4
2.7
2.9
3.3
3.5
4.7
0.3
0.1
0.1
5.2
65.0
Freshwater (on continents)
Terrestrial
Marine
Key Percentage of Earth’s
surface area
Average net primary
production (g/m2/yr)
60 50 40 30 20 10 0 2,500 2,000 1,500 1,000 500 0
Percentage of Earth’s net
primary production
25 20 15 10 5 0
125
2,500
360
1,500
500
3.0
90
900
600
800
2,200
600
250
1,600
1,200
1,300
2,000
700
140
0.3
7.9
9.1
9.6
5.4
3.5
0.6
7.1
4.9
3.8
2.3
24.4
5.6
1.2
0.9
0.1
0.04
0.9
22
Net primary production of different ecosystems
• Primary production affected by:
▫ Light availability (↑ depth, ↓ photosynthesis)
▫ Nutrient availability (N, P in marine env.)
• Key factors controlling primary production:
▫ Temperature & moisture
• A nutrient-rich lake that supports algae growth is
eutrophic.
Energy transfer between trophic levels is
typically only 10% efficient
• Production efficiency:
only fraction of E stored
in food
• Energy used in
respiration is lost as heat
• Energy flows (not cycle!)
within ecosystems
10% transfer of
energy from one
level to next
Ecological pyramids give insight to food chains
Pyramid of Numbers
Pyramid of Biomass
• Loss of energy limits #
of top-level carnivores
• Most food webs only
have 4 or 5 trophic
levels
Trophic level
Secondary
consumers
Primary
consumers
Primary
producers
The dynamics of energy through ecosystems have
important implications for the human population
Matter Cycles in Ecosystem
• Biogeochemical cycles: nutrient cycles that
contain both biotic and abiotic components
• organic inorganic parts of an ecosystem
• Nutrient Cycles: water, carbon, nitrogen,
phosphorus
Water Cycle
Carbon Cycle
• CO2 removed by
photosynthesis,
added by burning
fossil fuels
Nitrogen Cycle
• Nitrogen fixation:
▫ N2 plants by bacteria
• Nitrification:
▫ ammonium nitrite
nitrate
▫ Absorbed by plants
• Denitrification:
▫ Release N to atmosphere
Phosphorus Cycle
Restoration Ecology
• Bioremediation: use of organisms (prokaryotes,
fungi, plants) to detoxify polluted ecosystems
• Bioaugmentation: introduce desirable species
(eg. nitrogen-fixers) to add essential nutrients
Bioremediation of
groundwater contaminated
with uranium
Restoration ecology projects
Recommended