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PowerPoint Lectures for
Biology: Concepts & Connections, Sixth Edition
Campbell, Reece, Taylor, Simon, and Dickey
Chapter 37 Communities and Ecosystems
Lecture by Brian R. Shmaefsky
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Introduction: Hungry Hippos
All communities and ecosystems have certain features in common
Each type of ecosystem has its own unique structure and dynamics
Human activities can disrupt the balance of ecosystems
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COMMUNITY STRUCTURE AND DYNAMICS
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37.1 A community includes all the organisms inhabiting a particular area
Biological community
– An assemblage of populations living close enough together for potential interaction
– Described by its species composition
Boundaries of the community vary with research questions
– Can be a pond
– Can be the intestinal microbes of a pond organism
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Interspecific interactions
– Relationships with other species in the community
Interspecific competition
– Two different species compete for the same limited resource
– Squirrels and black bears
– Compete for acorns
37.2 Interspecific interactions are fundamental to community structure
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37.3 Competition may occur when a shared resource is limited
Ecological niche
– Sum of an organism’s use of biotic and abiotic resources
– Interspecific competition occurs when the niches of two populations overlap
Competition lowers the carrying capacity of competing populations
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Interspecific competition between orange-crowned warbler and Virginia’s warbler
37.3 Competition may occur when a shared resource is limited
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37.4 Mutualism benefits both partners
Reef-building corals require mutualism
– Photosynthetic dinoflagellates
– Live in the cells of each coral polyp
– Produce sugars used by the polyps
– Provide at least half of the energy used by the coral animals
Video: Clownfish and Anemone
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37.5 EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species
Predation benefits the predator but kills the prey
Prey adapt using protective strategies
– Camouflage
– Mechanical defenses
– Chemical defenses
Video: Seahorse Camouflage
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37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
Herbivory is not usually fatal
– Plants must expend energy to replace the loss
Plants have numerous defenses against herbivores
– Spines and thorns
– Chemical toxins
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Herbivores and plants undergo coevolution
– A change in one species acts as a new selective force on another
– Poison-resistant caterpillars seem to be a strong selective force for Passiflora plants
37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
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Eggs
Sugardeposits
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37.7 Parasites and pathogens can affect community composition
A parasite lives on or in a host from which it obtains nourishment
– Internal parasites include nematodes and tapeworms
– External parasites include mosquitoes and ticks
Pathogens are disease-causing parasites
– Pathogens can be bacteria, viruses, fungi, or protists
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Non-native pathogens can have rapid and dramatic impacts
– American chestnut devastated by chestnut blight protist
– A fungus-like pathogen currently causing sudden oak death on the West Coast
Non-native pathogens can cause a decline of the ecosystem
37.7 Parasites and pathogens can affect community composition
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37.8 Trophic structure is a key factor in community dynamics
Trophic structure
– A pattern of feeding relationships consisting of several different levels
Food chain
– Sequence of food transfer up the trophic levels
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Producers
– Support all other trophic levels
– Autotrophs
– Photosynthetic producers
– Plants on land
– Cyanobacteria in water
37.8 Trophic structure is a key factor in community dynamics
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Consumers
– Heterotrophs
– Primary consumers
– Secondary consumers
– Tertiary consumers
– Quaternary consumers
Detritivores and decomposers
– Derive energy from dead matter and wastes
37.8 Trophic structure is a key factor in community dynamics
Video: Shark Eating a Seal
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Plant
A terrestrial food chain
Producers Phytoplankton
An aquatic food chain
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Plant
A terrestrial food chain
Producers Phytoplankton
An aquatic food chain
Primaryconsumers
Grasshopper Zooplankton
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Plant
A terrestrial food chain
Producers Phytoplankton
An aquatic food chain
Primaryconsumers
Grasshopper Zooplankton
Secondaryconsumers
Mouse Herring
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Plant
A terrestrial food chain
Producers Phytoplankton
An aquatic food chain
Primaryconsumers
Grasshopper Zooplankton
Secondaryconsumers
Mouse Herring
Snake TunaTertiaryconsumers
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Plant
A terrestrial food chain
Producers Phytoplankton
An aquatic food chain
Primaryconsumers
Grasshopper Zooplankton
Secondaryconsumers
Mouse Herring
Snake TunaTertiaryconsumers
Hawk Killer whale
Quaternaryconsumers
Trophic level
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37.9 Food chains interconnect, forming food webs
Food web
– A network of interconnecting food chains
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Producers(plants)
Primaryconsumers
Secondaryand
primaryconsumers
Tertiaryandsecondaryconsumers
Quaternary,
tertiary,
and secondaryconsumers
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37.10 Species diversity includes relative abundance and species richness
Species diversity defined by two components
– Species richness
– Relative abundance
Plant species diversity in a community affects the animals
Species diversity has consequences for pathogens
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37.11 Keystone species have a disproportionate impact on diversity
Keystone species
– A species whose impact on its community is larger than its biomass or abundance indicates
– Occupies a niche that holds the rest of its community in place
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Keystone
Keystoneabsent
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37.12 Disturbance is a prominent feature of most communities
Disturbances
– Events that damage biological communities
– Storms, fire, floods, droughts, overgrazing, or human activity
– The types, frequency, and severity of disturbances vary from community to community
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Communities change drastically following a severe disturbance
Ecological succession
– Colonization by a variety of species
– A success of change gradually replaces other species
37.12 Disturbance is a prominent feature of most communities
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Primary succession
– Begins in a virtually lifeless area with no soil
Secondary succession
– When a disturbance destroyed an existing community but left the soil intact
37.12 Disturbance is a prominent feature of most communities
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Time
ShrubsAnnualplants
Perennialplants and
grasses
Softwood treessuch as pines
Hardwoodtrees
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37.13 CONNECTION: Invasive species can devastate communities
Introduction of rabbits in Australia
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Key
Frontier of rabbit spread Origin: 1860
600 Km
Australia
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ECOSYSTEM STRUCTURE AND DYNAMICS
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37.14 Ecosystem ecology emphasizes energy flow and chemical cycling
Ecosystem
– All the organisms in a community as well as the abiotic environment
Components of ecosystems
– Energy flow
– Passage of energy through the ecosystem
– Chemical cycling
– Transfer of materials within the ecosystem
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A terrarium has the components of an ecosystem
37.14 Ecosystem ecology emphasizes energy flow and chemical cycling
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Energyflow
Lightenergy
Chemical energy
Chemicalelements
Heatenergy
Bacteriaand fungi
Chemical cycling
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37.15 Primary production sets the energy budget for ecosystems
Primary production
– The amount of solar energy converted to chemical energy
– Carried out by producers
– Produces biomass
– Amount of living organic material in an ecosystem
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Primary production of different ecosystems
37.15 Primary production sets the energy budget for ecosystems
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Open ocean
Estuary
Algal beds and coral reefs
Desert and semidesert scrub
Tundra
Temperate grassland
Cultivated land
Boreal forest (taiga)
Savanna
Temperate deciduous forest
Tropical rain forest
0 500
Average net primary productivity (g/m2/yr)
1,000 1,500 2,5002,000
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37.16 Energy supply limits the length of food chains
A pyramid of production
– Illustrates the cumulative loss of energy transfer in a food chain
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1,000,000 kcal of sunlight
10 kcal
100 kcal
1,000 kcal
10,000 kcalProducers
Primaryconsumers
Secondaryconsumers
Tertiaryconsumers
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37.17 CONNECTION: A production pyramid explains why meat is a luxury for humans
The dynamics of energy flow apply to the human population
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Producers
Primaryconsumers
Secondaryconsumers
Humanmeat-eaters
Cattle
CornCorn
Humanvegetarians
Trophic level
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37.18 Chemicals are cycled between organic matter and abiotic reservoirs
Ecosystems are supplied with a continual influx of energy
– Sun
– Earth’s interior
Life also depends on the recycling of chemicals
– Organisms acquire chemicals as nutrients and lose chemicals as waste products
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Biogeochemical cycles
– Cycle chemicals between organisms and the Earth
– Can be local or global
Decomposers play a central role in biogeochemical cycles
37.18 Chemicals are cycled between organic matter and abiotic reservoirs
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Consumers
Geologic processes
Producers
Decomposers
Nutrientsavailableto producers
Abioticreservoir
4
1
2
3
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37.19 The carbon cycle depends on photosynthesis and respiration
Carbon is the major ingredient of all organic molecules
The return of CO2 to the atmosphere by respiration closely balances its removal by photosynthesis
The carbon cycle is affected by burning wood and fossil fuels
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Photosynthesis
Decomposers
(soil microbes)
Cellular respiration
Detritus
4
1
2
3
5
Plants, algae,cyanobacteria
Primaryconsumers
Higher-levelconsumers
Burning
CO2 in atmosphere
Plant litter;death
Wastes; death
Wood
and fossil
fuels
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37.20 The phosphorus cycle depends on the weathering of rock
Organisms require phosphorus for nucleic acids, phospholipids, and ATP
– Plants absorb phosphate ions in the soil and build them into organic compounds
– Phosphates are returned to the soil by decomposers
– Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor
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Animals
1Plants
Detritus
Decomposers
in soilDecomposition
Phosphatesin rock
Weatheringof rock
Runoff
Assimilation
Phosphates
in solution
Phosphatesin soil
(inorganic)
Precipitated(solid) phosphates
Rock
Upliftingof rock
6
3
2
4
5
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37.21 The nitrogen cycle depends on bacteria
Nitrogen is an essential component of proteins and nucleic acids
Nitrogen has two abiotic reservoirs
– Air
– Soil
Nitrogen fixation converts N2 to nitrogen used by plants
– Carried out by some bacteria and cyanobacteria
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Nitrogen (N2) in atmosphere
8 Plant Animal
Assimilation
by plants
Organiccompounds
Organiccompounds
Death; wastes
Denitrifiers
Nitratesin soil(NO3
–)
Detritus
Decomposers
DecompositionNitrifyingbacteria
Ammonium (NH4+)
in soil
Nitrogen fixation
Nitrogenfixation
Nitrogen-fixingbacteria in
root nodules
Free-livingnitrogen-fixingbacteria and
cyanobacteria
6
1
2
74
3
5
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37.22 CONNECTION: Ecosystem alteration can upset chemical cycling
Chemical cycling in an ecosystem depends on
– The web of feeding
– Relationships between plants, animals, and detritivores
– Geologic processes
Altering an environment can cause severe losses in chemical cycling
– Erosion
– Acid rain
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Deforested
Completion oftree cutting
Control
1968196719661965
80.0
60.0
40.0
20.0
4.0
3.0
2.0
1.0
0
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37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems
Major changes in terrestrial ecosystems disrupt chemical cycling
These changes can increase nutrients in aquatic ecosystems
– Algal and cyanobacteria blooms
– Eutrophication
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The most serious current threats
– Acid precipitation
– Changes in land use
– Climate warming
37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems
Video: Cyanobacteria (Oscillatoria)
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Decomposers
Producer
Energy flow
Chemical cycling
Herbivore(primary
consumer)
Carnivore(secondaryconsumer)
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chemicalelements
Ecosystems
involve the processes of
in which in which
makes a
from
fromareincorporated by
isconverted by
to chemicalenergy of
intocomponents of
detritivores returnelements to
which passthrough
one-waytrip
solar energy to
chemical energy
to heat
organicmolecules
(a) (b)
(c)
(d) (e)
(f)
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Copyright © 2009 Pearson Education, Inc.
You should now be able to
1. Describe the characteristics of a community
2. Explain how interspecific interactions affect the dynamics of populations
3. Describe the trophic structure of a community
4. Explain how species diversity is measured
5. Describe the role of environmental disturbance on ecological succession
6. Explain energy and nutrient cycling in ecosystems