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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 53
Community Ecology
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Communities in Motion
• A biological community is an assemblage of
populations of various species living close enough
for potential interaction
− For example, the “carrier crab” carries a sea
urchin on its back for protection against predators
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.1
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Community interactions are classified by whether
they help, harm, or have no effect on the species
involved
• Ecologists call relationships between species in a
community interspecific interactions
• Examples are competition, predation, herbivory,
symbiosis (parasitism, mutualism, and
commensalism), and facilitation
• Interspecific interactions can affect the survival
and reproduction of each species, and the effects
can be summarized as positive (+), negative (–),
or no effect (0)
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.UN03
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Competition
• Interspecific competition (–/– interaction) occurs
when species compete for a resource in short
supply
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Competitive Exclusion
• Strong competition can lead to competitive
exclusion, local elimination of a competing
species
• The competitive exclusion principle states that two
species competing for the same limiting resources
cannot coexist in the same place
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecological Niches and Natural Selection
• The total of a species’ use of biotic and abiotic
resources is called the species’ ecological niche
• An ecological niche can also be thought of as an
organism’s ecological role
• Ecologically similar species can coexist in a
community if there are one or more significant
differences in their niches
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Resource partitioning is differentiation of
ecological niches, enabling similar species to
coexist in a community
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.2
A. distichus perches on
fence posts and other
sunny surfaces.
A. insolitus usually
perches on shady
branches.
A. ricordii
A. aliniger
A. insolitus
A. distichus
A. christophei
A. cybotes
A. etheridgei
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• A species’ fundamental niche is the niche
potentially occupied by that species
• A species’ realized niche is the niche actually
occupied by that species
• As a result of competition, a species’ fundamental
niche may differ from its realized niche
– For example, the presence of one barnacle
species limits the realized niche of another
species
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.3
Chthamalus
Balanus
EXPERIMENT
Balanus
realized niche
Chthamalus
realized niche
High tide
Low tide
High tide
Chthamalus
fundamental niche
Low tideOcean
RESULTS
Ocean
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Character Displacement
• Character displacement is a tendency for
characteristics to be more divergent in sympatric
populations of two species than in allopatric
populations of the same two species
• An example is variation in beak size between
populations of two species of Galápagos finches
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.4
G. fuliginosa G. fortis
Los Hermanos
G. fuliginosa,
allopatric
G. fortis,
allopatric
Sympatric
populations
Santa María, San Cristóbal
Beak
depth
Beak depth (mm)
161412108
0
20
40
60
0
20
40
60
0
20
40
60
Daphne
Percentagesofindividualsineachsizeclass
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Predation
• Predation (+/– interaction) refers to interaction
where one species, the predator, kills and eats the
other, the prey
• Some feeding adaptations of predators are claws,
teeth, fangs, stingers, and poison
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Prey display various defensive adaptations
• Behavioral defenses include hiding, fleeing,
forming herds or schools, self-defense, and alarm
calls
• Animals also have morphological and
physiological defense adaptations
• Cryptic coloration, or camouflage, makes prey
difficult to spot
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cryptic coloration, or camouflage, makes prey
difficult to spot
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Animals with effective chemical defense often
exhibit bright warning coloration, called
aposematic coloration
• Predators are particularly cautious in dealing with
prey that display such coloration
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.5b
(b) Aposematic
coloration
Poison dart frog
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In some cases, a prey species may gain
significant protection by mimicking the appearance
of another species
• In Batesian mimicry, a palatable or harmless
species mimics an unpalatable or harmful model
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.5c
(c) Batesian mimicry: A harmless species mimics a harmful one.
Hawkmoth
larva
Green parrot snake
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In Müllerian mimicry, two or more unpalatable
species resemble each other
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.5d
(d) Müllerian mimicry: Two unpalatable species
mimic each other.
Cuckoo bee
Yellow jacket
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Herbivory
• Herbivory (+/– interaction) refers to an interaction
in which an herbivore eats parts of a plant or alga
• It has led to evolution of plant mechanical and
chemical defenses and adaptations by herbivores
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Symbiosis
• Symbiosis is a relationship where two or more
species live in direct and intimate contact with one
another
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Parasitism
• In parasitism (+/– interaction), one organism, the
parasite, derives nourishment from another
organism, its host, which is harmed in the process
• Parasites that live within the body of their host are
called endoparasites
• Parasites that live on the external surface of a host
are ectoparasites
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mutualism
• Mutualistic symbiosis, or mutualism (+/+
interaction), is an interspecific interaction that
benefits both species
• A mutualism can be
– Obligate, where one species cannot survive
without the other
– Facultative, where both species can survive
alone
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.7
(a) Acacia tree and ants (genus Pseudomyrmex)
(b) Area cleared by ants at the base of an acacia tree
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Commensalism
• In commensalism (+/0 interaction), one species
benefits and the other is neither harmed nor
helped
• Commensal interactions are hard to document in
nature because any close association likely affects
both species
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.8
A possible example of commensalism between cattle egrets and water buffalo
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Diversity and trophic structure characterize
biological communities
• In general, a few species in a community exert
strong control on that community’s structure
• Two fundamental features of community structure
are species diversity and feeding relationships
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Species Diversity
• Species diversity of a community is the variety of
organisms that make up the community
• It has two components: species richness and
relative abundance
– Species richness is the total number of different
species in the community
– Relative abundance is the proportion each
species represents of the total individuals in the
community
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.10
Community 1
A: 25% B: 25% C: 25% D: 25%
Community 2
A: 80% B: 5% C: 5% D: 10%
A B C D
Two communities can have the same species
richness but a different relative abundance
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Communities with higher diversity are
– More productive and more stable in their
productivity
– Better able to withstand and recover from
environmental stresses
– More resistant to invasive species, organisms
that become established outside their native
range
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Trophic Structure
• Trophic structure is the feeding relationships
between organisms in a community
• It is a key factor in community dynamics
• Food chains link trophic levels from producers to
top carnivores
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Carnivore
Carnivore
Herbivore
Carnivore
Plant
A terrestrial food chain
Carnivore
Carnivore
Carnivore
Zooplankton
Phytoplankton
A marine food chain
Quaternary
consumers
Tertiary
consumers
Secondary
consumers
Primary
consumers
Primary
producers
Figure 54.13
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Food Webs
• A food web is a branching food chain with
complex trophic interactions
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.14
Humans
Sperm
whales
Smaller
toothed
whales
Baleen
whales
Crab-
eater
seals
Leopard
seals
Elephant
seals
SquidsFishesBirds
Carniv-
orous
plankton
Cope-
pods
Euphau-
sids
(krill)
Phyto-
plankton
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Limits on Food Chain Length
• Each food chain in a food web is usually only a
few links long
• Two hypotheses attempt to explain food chain
length: the energetic hypothesis and the dynamic
stability hypothesis
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The energetic hypothesis suggests that length is
limited by inefficient energy transfer
– For example, a producer level consisting of 100
kg of plant material can support about 10 kg of
herbivore biomass (the total mass of all
individuals in a population)
• The dynamic stability hypothesis proposes that
long food chains are less stable than short ones
• Most data support the energetic hypothesis
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Species with a Large Impact
• Certain species have a very large impact on
community structure
• Such species are highly abundant or play a pivotal
role in community dynamics
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Dominant Species
• Dominant species are those that are most
abundant or have the highest biomass
• Dominant species exert powerful control over the
occurrence and distribution of other species
– For example, sugar maples have a major impact
on shading and soil nutrient availability in eastern
North America; this affects the distribution of other
plant species
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Keystone Species
• Keystone species exert strong control on a
community by their ecological roles, or niches
• In contrast to dominant species, they are not
necessarily abundant in a community
• Field studies of sea stars illustrate their role as a
keystone species in intertidal communities
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.17
EXPERIMENT
RESULTS
With Pisaster (control)
Without Pisaster
(experimental)
Year
’73’72’71’70’69’68’67’66’65’641963
0
5
10
15
20
Numberofspecies
present
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation of sea otter populations and their
predation shows how otters affect ocean
communities
© 2011 Pearson Education, Inc.
LE 53-17
100
80
60
40
0
20
Sea otter abundance
Otternumber
(%max.count)
400
300
200
0
100
Sea urchin biomass
Gramsper
0.25m2
10
8
6
4
0
2
Total kelp density
Numberper
0.25m2
19971993198919851972
Year
Food chain before
killer whale
involvement in
chain
Food chain after
killer whales started
preying on otters
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Ecosystem engineers (or “foundation species”)
cause physical changes in the environment that
affect community structure
– For example, beaver dams can transform
landscapes on a very large scale
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.19
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Facilitation
• Facilitation (+/+ or 0/+) describes an interaction
where one species can have positive effects on
another species without direct and intimate
contact
– For example, the black rush makes the soil more
hospitable for other plant species
© 2011 Pearson Education, Inc.
LE 53-19
Numberofplantspecies
8
6
4
0
2
Conditions
With
Juncus
Without
Juncus
Salt marsh with Juncus
(foreground)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Disturbance influences species diversity and
composition
• Decades ago, most ecologists favored the view
that communities are in a state of equilibrium
• Recent evidence of change has led to a
nonequilibrium model, which describes
communities as constantly changing after being
buffeted by disturbances
• A disturbance is an event that changes a
community, removes organisms from it, and alters
resource availability
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Characterizing Disturbance
• Fire is a significant disturbance in most terrestrial
ecosystems
• A high level of disturbance is the result of a high
intensity and high frequency of disturbance
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The intermediate disturbance hypothesis
suggests that moderate levels of disturbance can
foster greater diversity than either high or low
levels of disturbance
• High levels of disturbance exclude many slow-
growing species
• Low levels of disturbance allow dominant species
to exclude less competitive species
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The large-scale fire in Yellowstone National Park
in 1988 demonstrated that communities can often
respond very rapidly to a massive disturbance
• The Yellowstone forest is an example of a
nonequilibrium community
© 2011 Pearson Education, Inc.
LE 53-22
Soon after fire. As this photo taken soon after the fire
shows, the burn left a patchy landscape. Note the
unburned trees in the distance.
One year after fire. This photo of the same general area
taken the following year indicates how rapidly the com-
munity began to recover. A variety of herbaceous plants,
different from those in the former forest, cover the ground.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ecological Succession
• Ecological succession is the sequence of
community and ecosystem changes after a
disturbance
• Primary succession occurs where no soil exists
when succession begins
• Secondary succession begins in an area where
soil remains after a disturbance
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Early-arriving species and later-arriving species
may be linked in one of three processes
– Early arrivals may facilitate appearance of later
species by making the environment favorable
– They may inhibit establishment of later species
– They may tolerate later species but have no
impact on their establishment
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Retreating glaciers provide a valuable field-
research opportunity for observing succession
• Succession on the moraines in Glacier Bay,
Alaska, follows a predictable pattern of change in
vegetation and soil characteristics
1. The exposed moraine is colonized by pioneering
plants including liverworts, mosses, fireweed,
Dryas, willows, and cottonwood
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.22-1
Pioneer stage, with
fireweed dominant
Alaska
1760
Glacier
Bay
1860
1907
1941
1 0 5 10 15
Kilometers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
2. Dryas dominates the plant community
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.22-2
Pioneer stage, with
fireweed dominant
Alaska
1760
Glacier
Bay
1860
1907
1941
Dryas stage
1
2
0 5 10 15
Kilometers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
3. Alder invades and forms dense thickets
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.22-3
Pioneer stage, with
fireweed dominant
Alaska
1760
Glacier
Bay
1860
1907
1941
Dryas stage
Alder stage
1
2
3
0 5 10 15
Kilometers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
4. Alder are overgrown by Sitka spruce, western
hemlock, and mountain hemlock
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 54.22-4
Pioneer stage, with
fireweed dominant
Spruce stage
Alaska
1760
Glacier
Bay
1860
1907
1941
Dryas stage
Alder stage
1
4
2
3
0 5 10 15
Kilometers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Succession is the result of changes induced by
the vegetation itself
• On the glacial moraines, vegetation lowers the soil
pH and increases soil nitrogen content
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Successional stage
Pioneer Dryas Alder Spruce
0
10
20
30
40
50
Soilnitrogen(g/m2
) 60
Figure 54.23
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Biogeographic factors affect community
biodiversity
• Latitude and area are two key factors that affect a
community’s species diversity
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Latitudinal Gradients
• Species richness is especially great in the tropics
and generally declines along an equatorial-polar
gradient
• Two key factors in equatorial-polar gradients of
species richness are probably evolutionary history
and climate
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Temperate and polar communities have started
over repeatedly following glaciations
• The greater age of tropical environments may
account for the greater species richness
• In the tropics, the growing season is longer such
that biological time is faster
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Climate is likely the primary cause of the latitudinal
gradient in biodiversity
• Two main climatic factors correlated with
biodiversity are solar energy and water availability
• They can be considered together by measuring a
community’s rate of evapotranspiration
• Evapotranspiration is evaporation of water from
soil plus transpiration of water from plants
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Area Effects
• The species-area curve quantifies the idea that,
all other factors being equal, a larger geographic
area has more species
• A species-area curve of North American breeding
birds supports this idea
© 2011 Pearson Education, Inc.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Area (hectares; log scale)
Numberofspecies(logscale)
0.1 1 10 100 103
104
105
106
107
108
109
1010
1
10
100
1,000
Figure 54.26

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53 lectures ppt

  • 1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 53 Community Ecology
  • 2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Communities in Motion • A biological community is an assemblage of populations of various species living close enough for potential interaction − For example, the “carrier crab” carries a sea urchin on its back for protection against predators © 2011 Pearson Education, Inc.
  • 3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.1
  • 4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Community interactions are classified by whether they help, harm, or have no effect on the species involved • Ecologists call relationships between species in a community interspecific interactions • Examples are competition, predation, herbivory, symbiosis (parasitism, mutualism, and commensalism), and facilitation • Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0) © 2011 Pearson Education, Inc.
  • 5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.UN03
  • 6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competition • Interspecific competition (–/– interaction) occurs when species compete for a resource in short supply © 2011 Pearson Education, Inc.
  • 7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Competitive Exclusion • Strong competition can lead to competitive exclusion, local elimination of a competing species • The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place © 2011 Pearson Education, Inc.
  • 8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Niches and Natural Selection • The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche • An ecological niche can also be thought of as an organism’s ecological role • Ecologically similar species can coexist in a community if there are one or more significant differences in their niches © 2011 Pearson Education, Inc.
  • 9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community © 2011 Pearson Education, Inc.
  • 10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii A. aliniger A. insolitus A. distichus A. christophei A. cybotes A. etheridgei
  • 11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • A species’ fundamental niche is the niche potentially occupied by that species • A species’ realized niche is the niche actually occupied by that species • As a result of competition, a species’ fundamental niche may differ from its realized niche – For example, the presence of one barnacle species limits the realized niche of another species © 2011 Pearson Education, Inc.
  • 12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.3 Chthamalus Balanus EXPERIMENT Balanus realized niche Chthamalus realized niche High tide Low tide High tide Chthamalus fundamental niche Low tideOcean RESULTS Ocean
  • 13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Character Displacement • Character displacement is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species • An example is variation in beak size between populations of two species of Galápagos finches © 2011 Pearson Education, Inc.
  • 14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.4 G. fuliginosa G. fortis Los Hermanos G. fuliginosa, allopatric G. fortis, allopatric Sympatric populations Santa María, San Cristóbal Beak depth Beak depth (mm) 161412108 0 20 40 60 0 20 40 60 0 20 40 60 Daphne Percentagesofindividualsineachsizeclass
  • 15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Predation • Predation (+/– interaction) refers to interaction where one species, the predator, kills and eats the other, the prey • Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison © 2011 Pearson Education, Inc.
  • 16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Prey display various defensive adaptations • Behavioral defenses include hiding, fleeing, forming herds or schools, self-defense, and alarm calls • Animals also have morphological and physiological defense adaptations • Cryptic coloration, or camouflage, makes prey difficult to spot © 2011 Pearson Education, Inc.
  • 17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cryptic coloration, or camouflage, makes prey difficult to spot
  • 18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Animals with effective chemical defense often exhibit bright warning coloration, called aposematic coloration • Predators are particularly cautious in dealing with prey that display such coloration © 2011 Pearson Education, Inc.
  • 19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.5b (b) Aposematic coloration Poison dart frog
  • 20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In some cases, a prey species may gain significant protection by mimicking the appearance of another species • In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model © 2011 Pearson Education, Inc.
  • 21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.5c (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Green parrot snake
  • 22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In Müllerian mimicry, two or more unpalatable species resemble each other © 2011 Pearson Education, Inc.
  • 23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.5d (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Yellow jacket
  • 24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Herbivory • Herbivory (+/– interaction) refers to an interaction in which an herbivore eats parts of a plant or alga • It has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores © 2011 Pearson Education, Inc.
  • 25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiosis • Symbiosis is a relationship where two or more species live in direct and intimate contact with one another © 2011 Pearson Education, Inc.
  • 26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parasitism • In parasitism (+/– interaction), one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process • Parasites that live within the body of their host are called endoparasites • Parasites that live on the external surface of a host are ectoparasites © 2011 Pearson Education, Inc.
  • 27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mutualism • Mutualistic symbiosis, or mutualism (+/+ interaction), is an interspecific interaction that benefits both species • A mutualism can be – Obligate, where one species cannot survive without the other – Facultative, where both species can survive alone © 2011 Pearson Education, Inc.
  • 28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.7 (a) Acacia tree and ants (genus Pseudomyrmex) (b) Area cleared by ants at the base of an acacia tree
  • 29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Commensalism • In commensalism (+/0 interaction), one species benefits and the other is neither harmed nor helped • Commensal interactions are hard to document in nature because any close association likely affects both species © 2011 Pearson Education, Inc.
  • 30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.8 A possible example of commensalism between cattle egrets and water buffalo
  • 31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diversity and trophic structure characterize biological communities • In general, a few species in a community exert strong control on that community’s structure • Two fundamental features of community structure are species diversity and feeding relationships © 2011 Pearson Education, Inc.
  • 32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species Diversity • Species diversity of a community is the variety of organisms that make up the community • It has two components: species richness and relative abundance – Species richness is the total number of different species in the community – Relative abundance is the proportion each species represents of the total individuals in the community © 2011 Pearson Education, Inc.
  • 33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.10 Community 1 A: 25% B: 25% C: 25% D: 25% Community 2 A: 80% B: 5% C: 5% D: 10% A B C D Two communities can have the same species richness but a different relative abundance
  • 34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Communities with higher diversity are – More productive and more stable in their productivity – Better able to withstand and recover from environmental stresses – More resistant to invasive species, organisms that become established outside their native range © 2011 Pearson Education, Inc.
  • 35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Trophic Structure • Trophic structure is the feeding relationships between organisms in a community • It is a key factor in community dynamics • Food chains link trophic levels from producers to top carnivores © 2011 Pearson Education, Inc.
  • 36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carnivore Carnivore Herbivore Carnivore Plant A terrestrial food chain Carnivore Carnivore Carnivore Zooplankton Phytoplankton A marine food chain Quaternary consumers Tertiary consumers Secondary consumers Primary consumers Primary producers Figure 54.13
  • 37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food Webs • A food web is a branching food chain with complex trophic interactions © 2011 Pearson Education, Inc.
  • 38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.14 Humans Sperm whales Smaller toothed whales Baleen whales Crab- eater seals Leopard seals Elephant seals SquidsFishesBirds Carniv- orous plankton Cope- pods Euphau- sids (krill) Phyto- plankton
  • 39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Limits on Food Chain Length • Each food chain in a food web is usually only a few links long • Two hypotheses attempt to explain food chain length: the energetic hypothesis and the dynamic stability hypothesis © 2011 Pearson Education, Inc.
  • 40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The energetic hypothesis suggests that length is limited by inefficient energy transfer – For example, a producer level consisting of 100 kg of plant material can support about 10 kg of herbivore biomass (the total mass of all individuals in a population) • The dynamic stability hypothesis proposes that long food chains are less stable than short ones • Most data support the energetic hypothesis © 2011 Pearson Education, Inc.
  • 41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Species with a Large Impact • Certain species have a very large impact on community structure • Such species are highly abundant or play a pivotal role in community dynamics © 2011 Pearson Education, Inc.
  • 42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dominant Species • Dominant species are those that are most abundant or have the highest biomass • Dominant species exert powerful control over the occurrence and distribution of other species – For example, sugar maples have a major impact on shading and soil nutrient availability in eastern North America; this affects the distribution of other plant species © 2011 Pearson Education, Inc.
  • 43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Keystone Species • Keystone species exert strong control on a community by their ecological roles, or niches • In contrast to dominant species, they are not necessarily abundant in a community • Field studies of sea stars illustrate their role as a keystone species in intertidal communities © 2011 Pearson Education, Inc.
  • 44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.17 EXPERIMENT RESULTS With Pisaster (control) Without Pisaster (experimental) Year ’73’72’71’70’69’68’67’66’65’641963 0 5 10 15 20 Numberofspecies present
  • 45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Observation of sea otter populations and their predation shows how otters affect ocean communities © 2011 Pearson Education, Inc.
  • 46. LE 53-17 100 80 60 40 0 20 Sea otter abundance Otternumber (%max.count) 400 300 200 0 100 Sea urchin biomass Gramsper 0.25m2 10 8 6 4 0 2 Total kelp density Numberper 0.25m2 19971993198919851972 Year Food chain before killer whale involvement in chain Food chain after killer whales started preying on otters
  • 47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Ecosystem engineers (or “foundation species”) cause physical changes in the environment that affect community structure – For example, beaver dams can transform landscapes on a very large scale © 2011 Pearson Education, Inc.
  • 48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.19
  • 49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Facilitation • Facilitation (+/+ or 0/+) describes an interaction where one species can have positive effects on another species without direct and intimate contact – For example, the black rush makes the soil more hospitable for other plant species © 2011 Pearson Education, Inc.
  • 51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disturbance influences species diversity and composition • Decades ago, most ecologists favored the view that communities are in a state of equilibrium • Recent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances • A disturbance is an event that changes a community, removes organisms from it, and alters resource availability © 2011 Pearson Education, Inc.
  • 52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Characterizing Disturbance • Fire is a significant disturbance in most terrestrial ecosystems • A high level of disturbance is the result of a high intensity and high frequency of disturbance © 2011 Pearson Education, Inc.
  • 53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The intermediate disturbance hypothesis suggests that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance • High levels of disturbance exclude many slow- growing species • Low levels of disturbance allow dominant species to exclude less competitive species © 2011 Pearson Education, Inc.
  • 54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very rapidly to a massive disturbance • The Yellowstone forest is an example of a nonequilibrium community © 2011 Pearson Education, Inc.
  • 55. LE 53-22 Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance. One year after fire. This photo of the same general area taken the following year indicates how rapidly the com- munity began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.
  • 56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ecological Succession • Ecological succession is the sequence of community and ecosystem changes after a disturbance • Primary succession occurs where no soil exists when succession begins • Secondary succession begins in an area where soil remains after a disturbance © 2011 Pearson Education, Inc.
  • 57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Early-arriving species and later-arriving species may be linked in one of three processes – Early arrivals may facilitate appearance of later species by making the environment favorable – They may inhibit establishment of later species – They may tolerate later species but have no impact on their establishment © 2011 Pearson Education, Inc.
  • 58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Retreating glaciers provide a valuable field- research opportunity for observing succession • Succession on the moraines in Glacier Bay, Alaska, follows a predictable pattern of change in vegetation and soil characteristics 1. The exposed moraine is colonized by pioneering plants including liverworts, mosses, fireweed, Dryas, willows, and cottonwood © 2011 Pearson Education, Inc.
  • 59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.22-1 Pioneer stage, with fireweed dominant Alaska 1760 Glacier Bay 1860 1907 1941 1 0 5 10 15 Kilometers
  • 60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Dryas dominates the plant community © 2011 Pearson Education, Inc.
  • 61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.22-2 Pioneer stage, with fireweed dominant Alaska 1760 Glacier Bay 1860 1907 1941 Dryas stage 1 2 0 5 10 15 Kilometers
  • 62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3. Alder invades and forms dense thickets © 2011 Pearson Education, Inc.
  • 63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.22-3 Pioneer stage, with fireweed dominant Alaska 1760 Glacier Bay 1860 1907 1941 Dryas stage Alder stage 1 2 3 0 5 10 15 Kilometers
  • 64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4. Alder are overgrown by Sitka spruce, western hemlock, and mountain hemlock © 2011 Pearson Education, Inc.
  • 65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 54.22-4 Pioneer stage, with fireweed dominant Spruce stage Alaska 1760 Glacier Bay 1860 1907 1941 Dryas stage Alder stage 1 4 2 3 0 5 10 15 Kilometers
  • 66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Succession is the result of changes induced by the vegetation itself • On the glacial moraines, vegetation lowers the soil pH and increases soil nitrogen content © 2011 Pearson Education, Inc.
  • 67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Successional stage Pioneer Dryas Alder Spruce 0 10 20 30 40 50 Soilnitrogen(g/m2 ) 60 Figure 54.23
  • 68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biogeographic factors affect community biodiversity • Latitude and area are two key factors that affect a community’s species diversity © 2011 Pearson Education, Inc.
  • 69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Latitudinal Gradients • Species richness is especially great in the tropics and generally declines along an equatorial-polar gradient • Two key factors in equatorial-polar gradients of species richness are probably evolutionary history and climate © 2011 Pearson Education, Inc.
  • 70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Temperate and polar communities have started over repeatedly following glaciations • The greater age of tropical environments may account for the greater species richness • In the tropics, the growing season is longer such that biological time is faster © 2011 Pearson Education, Inc.
  • 71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Climate is likely the primary cause of the latitudinal gradient in biodiversity • Two main climatic factors correlated with biodiversity are solar energy and water availability • They can be considered together by measuring a community’s rate of evapotranspiration • Evapotranspiration is evaporation of water from soil plus transpiration of water from plants © 2011 Pearson Education, Inc.
  • 72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Area Effects • The species-area curve quantifies the idea that, all other factors being equal, a larger geographic area has more species • A species-area curve of North American breeding birds supports this idea © 2011 Pearson Education, Inc.
  • 73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Area (hectares; log scale) Numberofspecies(logscale) 0.1 1 10 100 103 104 105 106 107 108 109 1010 1 10 100 1,000 Figure 54.26

Notas do Editor

  1. Figure 54.1 Which species benefits from this interaction?
  2. Figure 54.UN03 Summary figure, Concept 54.1
  3. Figure 54.2 Resource partitioning among Dominican Republic lizards.
  4. Figure 54.3 Inquiry: Can a species ’ niche be influenced by interspecific competition?
  5. Figure 54.4 Character displacement: indirect evidence of past competition.
  6. Figure 54.5 Examples of defensive coloration in animals.
  7. Figure 54.5 Examples of defensive coloration in animals.
  8. Figure 54.5 Examples of defensive coloration in animals.
  9. Figure 54.7 Mutualism between acacia trees and ants.
  10. Figure 54.8 A possible example of commensalism between cattle egrets and water buffalo.
  11. Figure 54.10 Which forest is more diverse?
  12. Figure 54.13 Examples of terrestrial and marine food chains.
  13. Figure 54.14 An Antarctic marine food web.
  14. Figure 54.17 Inquiry: Is Pisaster ochraceus a keystone predator?
  15. Figure 54.19 Beavers as ecosystem engineers.
  16. Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  17. Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  18. Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  19. Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska.
  20. Figure 54.23 Changes in soil nitrogen content during succession at Glacier Bay.
  21. Figure 54.26 Species-area curve for North American breeding birds.