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LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
© 2011 Pearson Education, Inc.
Lectures byErin Barley
Kathleen Fitzpatrick
Ecosystems and Restoration Ecology
Chapter 55
Figure 55.1Blood Falls-Taylor Glacier in Antarctica: Bacteria lives on sulfur and iron containing ions.
The reduced iron in the water is oxidized and turns red
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 55.1: Physical laws govern energy flow and chemical cycling in ecosystems
• 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
• 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
• Ecologists study the transformations of energy and matter within their system
Fig. 55-4
Microorganismsand other
detritivores
Tertiary consumers
Secondaryconsumers
Primary consumers
Primary producers
Detritus
Heat
SunChemical cycling
Key
Energy flow
An overview of energy and nutrient dynamics in an ecosystem
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Conservation of Energy
• Laws of physics and chemistry apply to ecosystems, particularly energy flow
• The first law of thermodynamics states that energy cannot be created or destroyed, only transformed
• Energy enters an ecosystem as solar radiation, is conserved, and is lost from organisms as heat
• The second law of thermodynamics states that every exchange of energy increases the entropy of the universe
• In an ecosystem, energy conversions are not completely efficient, and some energy is always lost as heat
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Conservation of Mass
• The law of conservation of mass states that matter cannot be created or destroyed
• Chemical elements are continually recycled within ecosystems
• In a forest ecosystem, most nutrients enter as dust or solutes in rain and are carried away in water
• Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Energy, Mass, and Trophic Levels
• Autotrophs build molecules using photosynthesis or chemosynthesis as an energy source; 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)
• Detritivores (decomposers) are consumers that derive their energy from detritus, nonliving organic matter
• Prokaryotes and fungi are important detritivores
• Decomposition connects all trophic levels
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
• The extent of photosynthetic production sets the spending limit for an ecosystem’s energy budget
• The amount of solar radiation reaching the Earth’s surface limits photosynthetic output of ecosystems
• Only a small fraction of solar energy actually strikes photosynthetic organisms, and even less is of a usable wavelength
Fig. 55-5
Visible
Wavelength (nm)
Near-infrared
Liquid water
Soil
Vegetation
Clouds
Snow
Per
cen
t re
flec
tan
ce
0400 600 800 1,000 1,200
20
40
60
80
TECHNIQUEDetermining primary production with satellites
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 producers for respiration (autotrophic respiration Ra); Only NPP is available to consumers. NPP=GPP- Ra
• Ecosystems vary greatly in NPP
• Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit area
• Marine ecosystems are relatively unproductive per unit area, but contribute much to global NPP because of their volume
• In marine and freshwater ecosystems, both light and nutrients control primary production
• Depth of light penetration affects primary production in the photic zone of an ocean or lake, but, nutrients limit primary production in geographic regions of the ocean and in lakes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
• When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production
• An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration
Cellularrespiration
100 JGrowth
(new biomass)
Feces
200 J
33 J
67 J
Plant materialeaten by caterpillar
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Trophic Efficiency and Ecological Pyramids• Trophic efficiency is the percentage of production transferred
from one trophic level to the next: It ranges from ~5% to ~20%
• Trophic efficiency is multiplied over the length of a food chain
• Approximately 0.1% ofchemical energy fixedby photosynthesisreaches a tertiaryconsumer
• A pyramid of net production representsthe loss of energy witheach transfer in a foodchain
Primaryproducers
100 J
1,000,000 J of sunlight
10 J
1,000 J
10,000 J
Primaryconsumers
Secondaryconsumers
Tertiaryconsumers
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level
• Most biomass pyramids show a sharp decrease at successively higher trophic levels
• Certain aquatic ecosystems have inverted biomass pyramids: producers (phytoplankton) are consumed so quickly that they are outweighed by primary consumers
• Dynamics of energy flow in ecosystems have important implications for the human population
• Eating meat is a relatively inefficient way of tapping photosynthetic production; Worldwide agriculture could feed many more people if humans ate only plant material
Fig. 55-11
(a) Most ecosystems (data from a Florida bog)
Primary producers (phytoplankton)
(b) Some aquatic ecosystems (data from the English Channel)
Trophic level
Tertiary consumersSecondary consumers
Primary consumersPrimary producers
Trophic level
Primary consumers (zooplankton)
Dry mass(g/m2)
Dry mass(g/m2)
1.5
1137
809
214
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 55.4: Biological and geochemical processes cycle nutrients between organic and inorganic parts of an ecosystem
• Life depends on recycling chemical elements: Biogeochemical cycles involve biotic and abiotic components
• Carbon, oxygen, sulfur, and nitrogen occur in the atmosphere
• Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level
• Nutrient cycles include main reservoirs and processes that transfer elements between reservoirs; All elements cycle between organic and inorganic reservoirs
• In studying nutrient cycling, ecologists focus on:–Each chemical’s biological importance–Forms in which each chemical is available/used by organisms–Major reservoirs for each chemical–Key processes driving each chemical through its cycle
Reservoir AOrganic materialsavailable asnutrients
Livingorganisms,detritus
Reservoir BOrganicmaterialsunavailableas nutrients
Reservoir DInorganic materialsunavailableas nutrients
Reservoir CInorganic materialsavailable asnutrients
Fossilization
Burning offossil fuels
Assimilation,photosynthesis
Weathering,erosion
Formation ofsedimentary
rock
Respiration,decomposition,excretion
Peat
Coal
Oil
Mineralsin rocks
Soil
Atmosphere
Water
Figure 55.13
A general model of nutrient cycling
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Water Cycle• Water is essential to all organisms• 97% of the biosphere’s water is contained in the oceans, 2%
is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater; ground water is very important to humans
• Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater
The Carbon Cycle• Carbon-based organic molecules are essential to all life• Reservoirs include fossil fuels, soils, sediments, solutes in
oceans, plant and animal biomass, and the atmosphere
• CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere
Fig. 55-14a
Precipitationover land
Transportover land
Solar energy
Net movement ofwater vapor by wind
Evaporationfrom ocean
Percolationthroughsoil
Evapotranspirationfrom land
Runoff andgroundwater
Precipitationover ocean
Water cycles
Higher-levelconsumersPrimary
consumers
Detritus
Burning offossil fuelsand wood
Phyto-plankton
Cellularrespiration
Photo-synthesis
Photosynthesis
Carbon compoundsin water
Decomposition
CO2 in atmosphere
Carbonate rocks & fossil fuels: important sinks and reservoirs for carbon
Nutrient cycles
The Terrestrial Nitrogen Cycle
Nitrogen is in amino acids, proteins, and nucleic acids
The main reservoir of nitrogen is the atmosphere (N2), though this must be converted to NH4
+ or NO3– for uptake by plants, via nitrogen fixation by bacteria
Organic nitrogendecomposes to NH4
+ byammonification; NH4
+ isdecomposed to NO3
– bynitrification.
Denitrification convertsNO3
– back to N2
Decomposers
N2 in atmosphere
Nitrification
Nitrifyingbacteria
Nitrifyingbacteria
Denitrifyingbacteria
Assimilation
NH3 NH4 NO2
NO3
+ –
–
Ammonification
Nitrogen-fixingsoil bacteria
Nitrogen-fixingbacteria
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Phosphorus Cycle
• Major constituent of nucleic acids, phospholipids, and ATP
• Phosphate (PO43–) is the most important inorganic form of
phosphorus
• The largest reservoirs are sedimentary rockof marine origin, theoceans, andorganisms
• Phosphate binds withsoil particles, andmovement is oftenlocalized
Leaching
Consumption
Precipitation
Plantuptakeof PO4
3–
Soil
Sedimentation
Uptake
Plankton
Decomposition
Dissolved PO43–
Runoff
Geologicuplift
Weatheringof rocks
Concept 55.5: Restoration ecologists help return degraded ecosystems to a
more natural state
Given enough time, biological communities can recover from many types of disturbances
Restoration ecology seeks to initiate or speed up the recovery of degraded ecosystems
Two key strategies are bioremediation and augmentation of ecosystem processes
© 2011 Pearson Education, Inc.
Figure 55.17
(a) In 1991, before restoration (b) In 2000, near the completion of restoration
A gravel and clay mine site in New Jersey before and after restoration.
Some plants and lichens adapted to soils containing heavy metals can accumulate high Concentration of potentially toxic metals such as zinc, nickel, lead and cadmium in their tissuesLichens can grow on soil polluted with uranium dust
BioremediationBioremediation is the use of living organisms to
detoxify ecosystems
The organisms most often used are prokaryotes, fungi, or plants
These organisms can take up, and sometimes metabolize, toxic molecules
– For example, the bacterium Shewanella oneidensis can metabolize uranium and other elements to insoluble forms that are less likely to leach into streams and groundwater
© 2011 Pearson Education, Inc.
Days after adding ethanol
Co
nce
ntr
atio
n o
fso
lub
le u
ran
ium
(M
)6
5
4
3
2
1
04000 35030025020015010050
Figure 55.18
Bioremediation of groundwater contaminated with uranium at Oak Ridge National Laboratory, Tennessee.
Biological Augmentation
Biological augmentation uses organisms to add essential materials to a degraded ecosystem
– For example, nitrogen-fixing plants can increase the available nitrogen in soil
– For example, adding mycorrhizal fungi can help plants to access nutrients from soil
© 2011 Pearson Education, Inc.
You should now be able to:1. Explain how the first and second laws of thermodynamics apply
to ecosystems2. Define and compare gross primary production, net primary
production3. Explain why energy flows but nutrients cycle within an
ecosystem4. Explain what factors may limit primary production in aquatic
ecosystems5. Distinguish between the following pairs of terms: primary and
secondary production, production efficiency and trophic efficiency
6. Describe the four nutrient reservoirs and the processes that transfer the elements between reservoirs
8. Explain why toxic compounds usually have the greatest effect on top-level carnivores
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