Download Chapter 37 Communities and Ecosystems

Chapter 37
Communities and Ecosystems
PowerPoint Lectures for
Biology: Concepts & Connections, Sixth Edition
Campbell, Reece, Taylor, Simon, and Dickey
Lecture by Brian R. Shmaefsky
Copyright © 2009 Pearson Education, Inc.
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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37.2 Interspecific interactions are fundamental to
community structure
 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
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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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37.3 Competition may occur when a shared
resource is limited
 Interspecific competition between orange-crowned
warbler and Virginia’s warbler
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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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37.6 EVOLUTION CONNECTION: Herbivory
leads to diverse adaptations in plants
 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
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Eggs
Sugar
deposits
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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37.7 Parasites and pathogens can affect
community composition
 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
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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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37.8 Trophic structure is a key factor in
community dynamics
 Producers
– Support all other trophic levels
– Autotrophs
–
Photosynthetic producers
– Plants on land
– Cyanobacteria in water
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37.8 Trophic structure is a key factor in
community dynamics
 Consumers
– Heterotrophs
– Primary consumers
– Secondary consumers
– Tertiary consumers
– Quaternary consumers
 Detritivores and decomposers
– Derive energy from dead matter and wastes
Video: Shark Eating a Seal
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Plant
A terrestrial food chain
Producers
Phytoplankton
An aquatic food chain
Grasshopper
Plant
A terrestrial food chain
Primary
consumers
Zooplankton
Producers
Phytoplankton
An aquatic food chain
Mouse
Secondary
consumers
Herring
Grasshopper
Primary
consumers
Zooplankton
Producers
Phytoplankton
Plant
A terrestrial food chain
An aquatic food chain
Snake
Tertiary
consumers
Tuna
Mouse
Secondary
consumers
Herring
Grasshopper
Primary
consumers
Zooplankton
Producers
Phytoplankton
Plant
A terrestrial food chain
An aquatic food chain
Trophic level
Hawk
Quaternary
consumers
Killer whale
Snake
Tertiary
consumers
Tuna
Mouse
Secondary
consumers
Herring
Grasshopper
Primary
consumers
Zooplankton
Producers
Phytoplankton
Plant
A terrestrial food chain
An aquatic food chain
37.9 Food chains interconnect, forming food webs
 Food web
– A network of interconnecting food chains
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Quaternary,
tertiary,
and secondary
consumers
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Primary
consumers
Producers
(plants)
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
Keystone
absent
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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37.12 Disturbance is a prominent feature of most
communities
 Communities change drastically following a severe
disturbance
 Ecological succession
– Colonization by a variety of species
– A success of change gradually replaces other species
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37.12 Disturbance is a prominent feature of most
communities
 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
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Annual Perennial
plants plants and
grasses
Shrubs Softwood trees Hardwood
such as pines
trees
Time
37.13 CONNECTION: Invasive species can
devastate communities
 Introduction of rabbits in Australia
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600 Km
Australia
Key
Frontier of rabbit spread Origin: 1860
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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37.14 Ecosystem ecology emphasizes energy flow
and chemical cycling
 A terrarium has the components of an ecosystem
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Chemical cycling
Energy
flow
Chemical energy
Light
energy
Heat
energy
Chemical
elements
Bacteria
and fungi
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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37.15 Primary production sets the energy budget
for ecosystems
 Primary production of different 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
1,000
1,500
2,000
2,500
Average net primary productivity (g/m2/yr)
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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Tertiary
consumers
10 kcal
Secondary
consumers
100 kcal
Primary
consumers
1,000 kcal
Producers
10,000 kcal
1,000,000 kcal of sunlight
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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Trophic level
Secondary
consumers
Human
meat-eaters
Human
Primary
consumers vegetarians
Producers
Corn
Cattle
Corn
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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37.18 Chemicals are cycled between organic
matter and abiotic reservoirs
 Biogeochemical cycles
– Cycle chemicals between organisms and the Earth
– Can be local or global
 Decomposers play a central role in biogeochemical
cycles
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Consumers
3
2
Producers
Decomposers
1
Nutrients
available
to producers
Abiotic
reservoir
Geologic processes
4
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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CO2 in atmosphere
5 Burning
3
Cellular respiration
Photosynthesis
1
Higher-level
consumers
Wood
and fossil
fuels
Primary
consumers
Wastes; death
Decomposers
(soil microbes)
Plants, algae,
cyanobacteria
4
Detritus
2
Plant litter;
death
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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6
Uplifting
of rock
3
Weathering
of rock
Runoff
Phosphates
in rock
Animals
Plants
1
Assimilation
2
Phosphates
in solution
Detritus
Phosphates
in soil
(inorganic)
5
Rock
Precipitated
(solid) phosphates
Decomposition Decomposers
in soil
4
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
Animal
Plant
6
Assimilation
by plants
Organic
compounds
Nitrogen
fixation
Death; wastes
5
Denitrifiers
Organic
compounds
3
Nitrates
in soil
(NO3–)
Nitrogen-fixing
bacteria in
root nodules
Detritus
Free-living
nitrogen-fixing
bacteria and
cyanobacteria
Decomposers
4
1
Nitrifying
bacteria
7
Decomposition
Ammonium (NH4+)
in soil
Nitrogen fixation
2
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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80.0
60.0
Deforested
40.0
20.0
4.0
3.0
Completion of
tree cutting
Control
2.0
1.0
0
1965
1966
1967
1968
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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37.23 TALKING ABOUT SCIENCE: David
Schindler talks about the effects of nutrients
on freshwater ecosystems
 The most serious current threats
– Acid precipitation
– Changes in land use
– Climate warming
Video: Cyanobacteria (Oscillatoria)
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Producer
Herbivore
(primary
consumer)
Energy flow
Chemical cycling
Decomposers
Carnivore
(secondary
consumer)
Ecosystems
involve the processes of
(a)
(b)
in which
in which
makes a
chemical
elements
(c)
one-way
trip
from
solar energy to
chemical energy
to heat
is
are
from
converted by incorporated by
(d)
(e)
to chemical
into
energy of components of
organic
molecules
detritivores return
elements to
which pass
through
(f)
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
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