Transcript Chapter 45 part 2x - Tracy Jubenville Nearing

Dynamics of an Ecosystem
• In an ecosystem,
– Populations interact among themselves
– Populations interact with the physical
environment
– The abiotic components of an ecosystem are the
nonliving components:
• Atmosphere,
• Water,
• Soil
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Dynamic of an Ecosystem
–The biotic components of an
ecosystem are living things that can be
categorized according to their food
source:
• Autotrophs
• Heterotrophs
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Biotic Components: Autotrophs
• Producers are autotrophs
– Require only inorganic nutrients and an outside
energy source to produce organic nutrients
– Photoautotrophs
– Chemoautotrophs
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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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Biotic Components: Heterotrophs
• Consumers are heterotrophs
• Require a source of preformed organic nutrients
– Herbivores - Feed on plants
– Carnivores - Feed on other animals
– Omnivores - Feed on plants and animals
• Decomposers are also heterotrophs
– Bacteria and fungi
– 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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Energy Flow and Chemical Cycling
• 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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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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Energy Flow
• A food web
– Represents interconnecting paths of energy flow
– Describes trophic relationships
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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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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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Energy Flow
• 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
aboveground carnivores, so the detrital and grazing
food webs are joined.
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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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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 or 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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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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Biogeochemical Cycles
• Chemical cycling may involve:
– Reservoir - Source normally unavailable to producers
• Fossil Fuels
• Minerals
• Sediments
– Exchange Pool - Source from which organisms generally
take chemicals
• Atmosphere
• Soil
• Water
– 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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Hydrologic Cycle
• 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
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transpiration from plants
and evaporation from soil
H2O in Atmosphere
precipitation
over land
net transport of water vapor by wind
lake
evaporation
from ocean
precipitation
to ocean
freshwater runoff
Ocean
aquifer
Ice
Groundwaters
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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
destruction
of vegetation
4
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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Greenhouse Effect
• Greenhouse gases
–
–
–
–
Carbon dioxide, nitrous oxide, methane
Allow sunlight to pass through atmosphere
Reflect infrared back to earth
Trap heat in atmosphere
• 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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Phosphorus Cycle
• Phosphorus does not enter the atmosphere
– Sedimentary cycle
• Phosphate taken up by producers is incorporated into a
variety of organic molecules
– Excessive phosphorus levels can lead to water
eutrophication
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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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Nitrogen Cycle
• Atmospheric nitrogen is fixed by bacteria
– Make it 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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Nitrogen and Air Pollution
• 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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Review
• The Concept of the Community
• The Structure of Communities
–
–
–
–
–
–
Composition and Diversity
Habitat and Ecological Niche
Competition Between Populations
Predator-Prey Interactions
Symbiotic Relationships
Island Biogeography
• Community Development
– Ecological succession
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Review
• The Nature of Ecosystems
– Abiotic Components
– Autotrophs
– Heterotrophs
• Energy Flow
– Ecological Pyramids
• Biogeochemical Cycles
–
–
–
–
Hydrologic Cycle
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle
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(Both): © B. Runk/S. Schoenberger/Grant Heilman Photography
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