Download Chapter 36-Communities_Ecosystems

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 36
Communities and Ecosystems
Modules 36.1 – 36.4
From PowerPoint® Lectures for Biology: Concepts & Connections
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Dining In
• Wasps and Pieris caterpillars form an unusual
three-step food chain
• The 4-mm-long wasp Apanteles
glomeratus stabs through the
skin of a Pieris rapae caterpillar
and lays her eggs
– The caterpillar will be
destroyed from within as
the wasp larvae hatch and
nourish themselves on its
internal organs
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• Ichneumon wasps can detect when a Pieris
caterpillar contains Apanteles larvae
– A female ichneumon will pierce the caterpillar
and deposit her own eggs inside of the
Apanteles larvae
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• Finally, yet another wasp, a chalcid, may lay its
eggs inside the ichneumon larvae
• Usually, only the chalcids will emerge from
the dead husk of the caterpillar
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• A biological community derives its structure
from the interactions and interdependence of
the organisms living within it
• Ecosystem functioning depends on the
complex interactions between its community
of organisms and the physical environment
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36.1 A community is all the organisms inhabiting a
particular area
• All the organisms in a particular area make up
a community
• A number of factors characterize every
community
– Biodiversity
– The prevalent form of
vegetation
– Response to disturbances
– Trophic structure
(feeding relationships)
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Figure 36.1
• Biodiversity is the variety of different kinds of
organisms that make up a community
• Biodiversity has two components
– Species richness, or the total number of
different species in the community
– The relative abundance of different species
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STRUCTURAL FEATURES OF COMMUNITIES
36.2 Competition may occur when a shared
resource is limited
• Interspecific competition occurs between two
populations if they both require the same
limited resource
• A population's niche is its role in the
community
– The sum total of its use of the biotic and abiotic
resources of its habitat
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• The competitive exclusion principle
– Populations of two species cannot coexist in a
community if their niches are nearly identical
High
tide
Chthamalus
Balanus
Ocean
Low
tide
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Figure 36.2
• Competition between species with identical
niches has two possible outcomes
– One of the populations, using resources more
efficiently and having a reproductive
advantage, will eventually eliminate the other
– Natural selection may lead to resource
partitioning
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36.3 Predation leads to diverse adaptations in both
predator and prey
• Predation is an interaction where one species
eats another
– The consumer is called the predator and the
food species is known as the prey
• Parasitism can be considered a form of
predation
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• As predators adapt to prey, sometimes natural
selection also shapes the prey's defenses
• This process of
reciprocal
adaptation is
known as
coevolution
– Example:
Heliconius and
the passionflower
vine
Eggs
Sugar
deposits
Figure 36.3A
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• Prey gain protection against predators through
a variety of defense mechanisms
– Mechanical defenses, such as the quills of a
porcupine
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• Chemical defenses are widespread and very
effective
– Animals with effective chemical defenses are
often brightly colored to warn predators
– Example: the poison-arrow frog
Figure 36.3B
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• Camouflage is a very common defense in the
animal kingdom
– Example: the gray tree frog
Figure 36.3C
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• Batesian mimicry occurs when a palatable or
harmless species mimics an unpalatable or
harmful one
– The mimicry can even involve behavior
– This hawkmoth larva puffs up its head to
mimic the head of a snake
Figure 36.3D
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• Müllerian mimicry is when two unpalatable
species that inhabit the same community
mimic each other
– Example: the cuckoo bee and the yellow jacket
Figure 36.3E
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36.4 Predation can maintain diversity in a
community
• A keystone species exerts strong control on
community structure because of its ecological
role
• A keystone predator may maintain community
diversity by reducing
the numbers of the
strongest competitors
in a community
– This sea star is a
keystone predator
Figure 36.4A
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• Predation by killer whales
on sea otters, allowing sea
urchins to overgraze on kelp
– Sea otters represent the
keystone species
Figure 36.4B
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