Download 53 Community Ecology 7 - Mid

Chapter 53
Community Ecology
PowerPoint TextEdit Art Slides for
Biology, Seventh Edition
Neil Campbell and Jane Reece
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Figure 53.1 A savanna community in Chobe National
Park, Botswana
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Figure 53.2 Can a species’ niche be influenced by
interspecific competition?
EXPERIMENT
Ecologist Joseph Connell studied two baranacle
speciesBalanus balanoides and Chthamalus stellatusthat have a
stratified distribution on rocks along the coast of Scotland.
When Connell removed Balanus from the
lower strata, the Chthamalus population spread into that area.
High tide
Chthamalus
Balanus
RESULTS
High tide
Chthamalus
realized niche
Chthamalus
fundamental niche
Balanus
realized niche
Ocean
Low tide
In nature, Balanus fails to survive high on the rocks because it is
unable to resist desiccation (drying out) during low tides. Its realized
niche is therefore similar to its fundamental niche. In contrast,
Chthamalus is usually concentrated on the upper strata of rocks. To
determine the fundamental of niche of Chthamalus, Connell removed
Balanus form the lower strata.
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Ocean
CONCLUSION
Low tide
The spread of Chtamalus when Balanus was
removed indicates that competitive exclusion makes the realized
niche of Chthamalus much smaller than its fundamental niche.
• Classic experiments confirm this.
Fig. 53.2
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Figure 53.3 Resource partitioning among Dominican
Republic lizards
A. insolitus
usually perches
on shady branches.
A. ricordii
A. distichus
perches on
fence posts
and other
sunny
surfaces.
A. insolitus
A. alinigar
A. distichus
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A. christophei
A. cybotes
A. etheridgei
Character displacement is the tendency for
characteristics to be more divergent in
sympatric populations of two
species than in
allopatric
populations
of the same two
species.
– Hereditary changes
evolve that bring
about resource
partitioning.
Fig. 53.4
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Figure 53.5 Cryptic coloration: canyon tree frog
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Holding the line of its near vertical posture, a yellow
trumpetfish swims gracefully in the waters of the
Tuamotu archipelago in French Polynesia. Trumpetfish
tend to align themselves with other vertical objects,
often hiding alongside larger upright-oriented fish to
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get closer
to prey
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• Mechanical defenses include spines.
• Chemical defenses include odors and
toxins
• Aposematic coloration is indicated by
warning colors, and is sometimes
associated with other defenses (toxins).
Fig. 53.6
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Figure 53.7 Batesian mimicry: A harmless species
mimics a harmful one
(b) Green parrot snake
(a) Hawkmoth larva
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Red and Yellow
kills a fellow, Red
and Black is safe
for Jack.
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Figure 53.8 Müllerian mimicry: Two unpalatable
species mimic each other
(a) Cuckoo bee
(b) Yellow jacket
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1. Populations may be linked by competition, predation,
mutualism and commensalism
• Possible interspecific interactions are introduced in
Table 53.1, and are symbolized by the positive or
negative affect of the interaction on the individual
populations.
Symbiosis
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– Parasites and pathogens as predators.
• A parasite derives nourishment from a host,
which is harmed in the process.
• Pathogens are disease-causing organisms
that can be considered predators.
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Endoparasites
live inside the
host
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ectoparasites
live on the
surface of the
host.
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•Parasitoidism is a special type of parasitism where the
parasite eventually kills the host.
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Figure 53.9 Mutualism between acacia trees and ants
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• Mutualism is where
two species benefit
from their
interaction.
Fig. 53.9
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Figure 53.10 A possible example of commensalism
between cattle egrets and water buffalo
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Majestic in purple, a spotted cleaner shrimp in the waters off Bonaire Island in the Caribbean
works hard for its customers. This cleaner shrimp (Periclimenes yucatanicus) associates with
a sea anemone and attracts fish from which it cleans and eats detritus such as parasites and
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algae. Such a symbiotic relationship benefits both the shrimp and the fish
Commensalism is where one species benefits from
the interaction, but other is not affected. An example
would be barnacles that attach to a whale.
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• Coevolution and interspecific interactions.
– Coevolution refers to reciprocal
evolutionary adaptations of two
interacting species.
• When one species evolves, it exerts
selective pressure on the other to
evolve to continue the interaction.
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Flower is white
and blooms at
night
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Flower is red and
nectar is at the end of
a long tube
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Figure 53.11 Which forest is more diverse?
A
B
C
D
A: 25%
Community 1
B: 25%
C: 25%
D: 25%
A: 80%
Community 2
B: 5%
C: 5%
D: 10%
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2. Species richness generally declines along an
equatorial-polar gradient
• Tropical habitats support
much larger numbers of
species of organisms
than do temperate and
polar regions.
• In aquatic systems,
biodiversity increases
with depth.
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2. Trophic structure is a key factor in community
dynamics
• The trophic structure of a community is
determined by the feeding relationships
between organisms.
• The transfer of food energy from its source in
photosynthetic organisms through herbivores
and carnivores is called the food chain.
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• Charles Elton first
pointed out that the
length of a food chain
is usually four or five
links, called trophic
levels.
• He also recognized
that food chains are
not isolated units but
are hooked together
into food webs.
Fig. 53.10
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• Food webs.
– Who eats whom in a
community?
– Trophic relationships
can be diagrammed in
a community.
– What transforms
food chains into
food webs?
– A given species may
weave into the web at
more than one trophic
level.
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Fig. 53.11
Figure 53.14 Partial food web for the Chesapeake
Bay estuary on the U.S. Atlantic coast
Juvenile striped bass
Sea nettle
Fish larvae
Fish eggs
Zooplankton
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– What limits the length of a food chain?
• The energetic hypothesis suggests that the
length of a food chain is limited by the
inefficiency of energy transfer along the
chain.
• The dynamic stability hypothesis states
that long food chains are less stable than
short chains.
Fig. 53.13
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Figure 53.16 Testing a keystone predator hypothesis
Number of species
present
(a) The sea star Pisaster
ochraceous feeds
preferentially on mussels but
will consume other
invertebrates.
With Pisaster (control)
20
15
10
Without Pisaster (experimental)
5
0
1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73
(b) When Pisaster was removed from an intertidal zone, mussels eventually
took over the rock face and eliminated most other invertebrates and algae.
In a control area from which Pisaster was not removed, there was little
change in species diversity.
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Figure 53.17 Sea otters as keystone predators in
the North Pacific
Otter number
(% max. count)
100
80
60
40
20
0
(a) Sea otter abundance
Grams per
0.25 m2
400
Number per
0.25 m2
300
200
100
0
(b) Sea urchin biomass
Food chain before
killer whale involvement in chain
10
8
6
4
2
0
1972 1985 1989 1993 1997
Year
(c) Total kelp density
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Food chain after killer
whales started preying
on otters
Figure 53.18 Beavers as ecosystem “engineers” in
temperate and boreal forests
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Figure 53.19 Facilitation by black rush (Juncus
gerardi) in New England salt marshes
Number of plant species
8
6
4
2
0
Salt marsh with Juncus
(foreground)
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With
Juncus
Without
Juncus
Conditions
Figure 53.20 Relationship between rainfall and herbaceous
plant cover in a desert shrub community in Chile
Percentage of
herbaceous plant cover
100
75
50
25
0
0
100
200
Rainfall (mm)
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300
400
Unnumbered figure page 1171
Polluted State
Fish
Restored State
Abundant
Rare
Zooplankton
Rare
Abundant
Algae
Abundant
Rare
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Figure 53.21 Long-term effects of fire on a tallgrass
prairie community in Kansas
(a) Before a controlled burn.
A prairie that has not burned for
several years has a high proportion of detritus (dead grass).
(b) During the burn. The detritus
serves as fuel for fires.
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(c) After the burn. Approximately one
month after the controlled burn,
virtually all of the biomass in this
prairie is living.
Figure 53.22 Patchiness and recovery following a
large-scale disturbance
(a) 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.
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( b) One year after fire. This photo of the same general area taken the
following year indicates how rapidly the community began to
recover. A variety of herbaceous plants, different from those in the
former forest, cover the ground.
Figure 53.23 A glacial retreat in southeastern Alaska
Grand
Pacific Gl.
1940
Canada
Alaska
0
1912
1948
1879
1935 1949
Miles
1941
1 899
1907
5
1879
1948
1931
1911
1900
1892
1879
1913
1860
Reid Gl.
Johns Hopkins
Gl.
1879
Glacier
Bay
1830
1780
1760
Pleasant Is.
McBride glacier retreating
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10
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Figure 53.24 Changes in plant community structure and
soil nitrogen during succession at Glacier Bay, Alaska
(a) Pioneer stage, with fireweed dominant
(b) Dryas stage
60
Soil nitrogen (g/m2)
50
40
30
20
10
0
Pioneer Dryas Alder Spruce
Successional stage
(c) Spruce stage
(d) Nitrogen fixation by Dryas and alder
increases the soil nitrogen content.
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Located between Java and
Sumatra in the Sunda
Strait, Krakatoa's 1883
eruption wreaked havoc for
great distances when nearly
11 cubic miles (17.7 cubic
kilometers) of ash and rock
launched into the air, 120foot (37-meter) tsunamis
raced 6 miles (9.6
kilometers) inland, and
entire villages were
destroyed. Thirty-six
thousand people were
killed. The megablast was
so powerful it blew the
mountain to bits, leaving
behind craggy islets and a
new cone, Anak Krakatau,
or "Krakatoa's baby," in
what is now Indonesia's
premier national park,
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• Secondary succession occurs where an
existing community has been cleared by some
event, but the soil is left intact.
– Grasses grow first, then trees and other
organisms.
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• Soil concentrations of
nutrients show changes
over time.
Fig. 53.20
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Figure 53.25 Energy, water, and species richness
180
160
Tree species richness
140
120
100
80
60
40
20
0
100
(a) Trees
900
700
500
300
Actual evapotranspiration (mm/yr)
1,100
Vertebrate species richness
(log scale)
200
100
50
10
1
(b) Vertebrates
500
1,000
1,500
Potential evapotranspiration (mm/yr)
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2,000
Figure 53.26 Species-area curve for North American
breeding birds
Number of species (log scale)
1,000
100
10
1
1
10
100 103
104
105
106
Area (acres)
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107
108
109 1010
Rate of immigration or extinction
Rate of immigration or extinction
Rate of immigration or extinction
Figure 53.27 The equilibrium model of island biogeography
Equilibrium number
Number of species on island
(a) Immigration and extinction rates. The
equilibrium number of species on an
island represents a balance between the
immigration of new species and the
extinction of species already there.
Small island
Large island
Number of species on island
(b) Effect of island size. Large islands may
ultimately have a larger equilibrium number of species than small islands because
immigration rates tend to be higher and
extinction rates lower on large islands.
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Far island
Near island
Number of species on island
(c) Effect of distance from mainland.
Near islands tend to have larger
equilibrium numbers of species than
far islands because immigration rates
to near islands are higher and extinction
rates lower.
Figure 53.28 How does species richness relate to
area?
FIELD STUDY Ecologists Robert MacArthur and E. O. Wilson
studied the number of plant species on the Galápagos Islands,
which vary greatly in size, in relation to the area of each island.
RESULTS
Number of plant species (log scale)
400
200
100
50
25
10
5
0
0.1
10
1
100
1,000
(mi2)
Area of island
(log scale)
CONCLUSION The results of the study showed that plant
species richness increased with island size, supporting the
species-area theory.
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(a) Integrated
hypothesis. Communities are
discrete groupings of particular species that
are closely interdependent and nearly
always occur together.
Population
densities of
individual
species
Figure 53.29 Testing the integrated and individualistic
hypotheses of communities
(b) Individualistic hypothesis. Species are
independently distributed along gradients
and a community is simply the assemblage
of species that occupy the same area
because of similar abiotic needs.
Population
densities of
individual
species
Environmental gradient
(such as temperature or moisture)
(c) Trees in the Santa Catalina Mountains. The distribution of tree
species at one elevation in the Santa Catalina Mountains of
Arizona supports the individualistic hypothesis. Each tree species
has an independent distribution along the gradient, apparently
conforming to its tolerance for moisture, and the species that
live together at any point along the gradient have similar
physical requirements. Because the vegetation changes
continuously along the gradient, it is impossible to delimit
sharp boundaries for the communities.
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Number of
plants
per hectare
Environmental gradient
(such as temperature or moisture)
600
400
200
0
Wet
Moisture gradient
Dry