Transcript Biotic Components: Producers

Biotic Components: Producers
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a. Producers
a(Left): © Ed Reschke/Peter Arnold, Inc.; a(Right): © Herman Eisenbeiss/Photo Researchers, Inc.
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Dynamics of an Ecosystem
• Heterotrophs
– Need a preformed source of organic nutrients as they
acquire food
– Consumers – consume food generated by a producer
• Herbivores - Feed on plants
• Carnivores - Feed on other animals
• Omnivores - Feed on plants and animals
• Detritivores – Feed on decomposing organic matter
• Decomposers – Break down dead organic matter
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Biotic Components: Herbivores
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b. Herbivores
b(Left): © Royalty-free/Corbis; b(Right): © Gerald C. Kelley/Photo Researchers, Inc.
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Biotic Components: Carnivores
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c. Carnivores
c(Left): © Bill Beatty/Visuals Unlimited; c(Right): © Joe McDonald/Visuals Unlimited
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Biotic Components: Decomposers
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d. Decomposers
d(Left): © SciMAT/Photo Researchers, Inc.; d(Right): © Michael Beug
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Dynamics of an Ecosystem
• Energy Flow
– Every ecosystem is characterized by two fundamental
phenomena:
• Energy flow
–
–
–
–
–
Begins when producers absorb solar energy
Make organic nutrients via photosynthesis
Organic nutrients are used by themselves
Organic nutrients are used by others
Energy eventually dissipates into the environment as heat
• Chemical cycling
– Begins when producers take in inorganic nutrients from the physical
environment
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Nature of an Ecosystem
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solar
energy
heat
producers
consumers
Inorganic
nutrient pool
heat
heat
decomposers
energy
nutrients
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Dynamics of an Ecosystem
• Energy Flow
– Energy flows through an ecosystem via photosynthesis
– Only a portion (10%) of the organic nutrients made by
producers is passed on to consumers
• Organisms use organic molecules to fuel their own metabolism,
growth, and reproduction
• Additional energy is lost through excretion, defecation, and
organisms that die without being consumed
• A food web
– Represents interconnecting paths of energy flow
– Describes trophic relationships
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Energy Balances
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Heat to
environment
cellular respiration
death
growth and reproduction
Energy to
carnivores
Energy
to detritus
feeders
© George D. Lepp/Photo Researchers, Inc.
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Dynamics of an Ecosystem
• Energy Flow
– A food web
• Represents interconnecting paths of energy flow within
ecosystems
• Describes trophic (feeding) relationships
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Dynamics of an Ecosystem
• An Example of Energy Flow
– A grazing food web begins with a producer, in this
case an oak tree.
– Insects, rabbits, and deer feed on leaves.
– Birds, chipmunks, and mice feed on fruits and nuts.
• They are omnivores because they also feed on
caterpillars.
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Dynamics of an Ecosystem
• An Example of Energy Flow (continued)
– A detrital food web begins with detritus
• Detritus is food for soil organisms such as earthworms.
• Earthworms are in turn fed on by carnivorous invertebrates.
• Invertebrates may be eaten by shrews or salamanders.
– A detrital food web member may become food for above
ground carnivores, so the detrital and grazing food webs are
joined.
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Grazing and Detrital Food Web
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Autotrophs
Herbivores/Omnivores
Carnivores
owls
nuts
birds
hawks
leaf-eating
insects
deer
foxes
leaves
chipmunks
rabbits
skunks
snakes
detritus
mice
mice
a.
death
death
fungi and bacteria in detritus
death
invertebrates
carnivorous invertebrates
salamanders
shrews
b.
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Dynamics of an Ecosystem
• Trophic Levels
– A food chain is a diagram showing a single path of
energy flow in an ecosystem.
– Trophic level
• A level of nourishment within a food web or chain
• Composed of all the organisms that feed at the same
level in a food chain
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Dynamics of an Ecosystem
• Ecological Pyramids
 Only about 10% of the energy of one trophic level
is available to the next trophic level
• Explains why few top carnivores can be supported in a
food web
 Ecological pyramids
• Depict the flow of energy with large losses between
successive trophic levels
• May be based on the number of organisms or the
amount of biomass at each trophic level
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Ecological Pyramid
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top carnivores
1.5 g/m2
carnivores
11 g/m2
herbivores
37 g/m2
autotrophs
809 g/m2
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Dynamics of an Ecosystem
• Ecological Pyramids
– Pyramids of biomass
• Biomass
– Number of organisms x dry weight of the organic matter within
one organism
• Biomass of the producers is expected to exceed the
herbivores, which should exceed that of the carnivores
• In aquatic ecosystems, the herbivores may have a
greater biomass than the producers due to the fact the
aquatic algae are consumed at such a high rate
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Inverted Pyramid of Biomass
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zooplankton
phytoplankton
relative
dry weight
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Dynamics of an Ecosystem
• Chemical Cycling
 The pathways by which chemicals circulate through
ecosystems
• Involve both living (biotic) and nonliving (geologic)
components
• Known as biogeochemical cycles
–
–
–
–
Water Cycle
Carbon Cycle
Phosphorus Cycle
Nitrogen Cycle
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Dynamics of an Ecosystem
• Chemical Cycling
– May involve:
• Reservoir - Source normally unavailable to producers
– Ex: carbon present in calcium carbonate shells on ocean bottoms
• Exchange Pool - Source from which organisms generally
take chemicals
– Ex: Atmosphere, soil
• Biotic Community - Chemicals remain in food chains,
perhaps never entering a pool
– Human activities result in pollution because they upset the
normal balance of nutrients
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Model for Chemical Cycling
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Reservoir
• fossil fuels
• mineral
in rocks
• sediment
in oceans
Exchange
Pool
• atmosphere
• soil
• water
producers
Community
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Dynamics of an Ecosystem
• The Water (hydrologic) Cycle
 Transfer rate
• The amount of a substance that moves from one
component of the environment to another with a
specified period of time
 Fresh water evaporates from bodies of water
 Precipitation on land enters the ground, surface
waters, or aquifers
 Water eventually returns to the oceans
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The Hydrologic (Water) Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
transpiration from plants
and evaporation from soil
H2O in Atmosphere
precipitation
over land
net transport of water vapor by wind
lake
precipitation
to ocean
evaporation
from ocean
freshwater runoff
Ocean
aquifer
Ice
Groundwaters
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Dynamics of an Ecosystem
• The Carbon Cycle
– Atmosphere is an exchange pool for carbon dioxide
– In water, carbon dioxide combines with water to produce
bicarbonate ions
– Bicarbonate in the water is in equilibrium with carbon
dioxide in the air
– The total amount of carbon dioxide in the atmosphere has
been increasing every year due to human activities such
as fossil fuel combustion
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The Carbon Cycle
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combustion
CO2 in Atmosphere
2
6
photosynthesis
4
destruction
of vegetation
respiration
decay
1
5
Land plants
6
diffusion
Ocean
3
runoff
coal
bicarbonate (HCO3–)
Soils
sedimentation
oil
natural
gas
dead organisms
and animal waste
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Dynamics of an Ecosystem
• The Carbon Cycle (continued)
– Greenhouse effect
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•
•
•
•
Carbon dioxide, nitrous oxide, methane
Allow sunlight to pass through atmosphere
Reflect infrared back to earth
Trap heat in atmosphere
Leads to global warming and climate change
– If Earth’s temperature rises
• More water will evaporate
• More clouds will form, and
• Setting up a potential positive feedback loop
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Dynamics of an Ecosystem
• The Phosphorous Cycle
 Phosphorous from ocean sediments moves on to land via
geologic activity
 Weathering of rocks results in the deposition of phosphate
ions in the soil
 Phosphate ions become available to plants
 Animals obtain phosphate by consuming producers
 Death and decay returns phosphate ions to the soil, and to
producers, again.
 Some phosphate runs off into aquatic ecosystems
• Excessive phosphorous levels can lead to eutrophication
– Over-enrichment of waterways
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The Phosphorus Cycle
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mineable rock
2
8
weathering
phosphate mining
sewage treatment
plants
geologic uplift
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fertilizer
4
1
phosphate
in solution
8
plants
runoff
5
animals
organisms
Biotic
Community
phosphate
in soil
Ocean
3
plant and
animal wastes
detritus
6
decomposers
sedimentation
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Dynamics of an Ecosystem
• Nitrogen Cycle
 Atmospheric nitrogen is fixed (nitrogen fixation) by
bacteria
• Made available to plants
• Nodules on legume roots
 Nitrification - Production of nitrates, which plants
can use as a source of nitrogen
 Assimilation-plants take up ammonium and
nitrates from the soil and use them to produce
proteins and nucleic acids
 Denitrification - Conversion of nitrate to nitrous
oxide and nitrogen gas
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The Nitrogen Cycle
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N2 in Atmosphere
1
N2 fixation
denitrification
nitrogen-fixing
bacteria in nodules
and soil
N2 fixation
runoff
human
activities
plants
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3
4
2
denitrifying bacteria
nitrification
plant and
animal waste
2
1
decomposers
NH4+
cyanobacteria
Biotic
Community
Biotic
Community
3
NH4+
denitrification
2
phytoplankton
4
nitrifying
bacteria
NO3
NO3-
-
decomposers
NO3denitrifying
bacteria
sedimentation
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Dynamics of an Ecosystem
• Human activities and the Nitrogen Cycle
– Acid Deposition
• Nitrogen oxides and sulfur dioxide are converted to acids
when they combine with water vapor
• Affects lakes and forests
• Reduces agricultural yield
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