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Chapter 8
Community Ecology:
Structure, Species
Interactions, Succession,
and Sustainability
Miller – Living in the Environment
13th Edition
Most Species Rich Environments
Tropical rainforests
Coral reefs
The deep sea
Large tropical lakes
Roles of Species in Ecosystems
 native
 non-native
 indicator
 keystone
Native and Non-native Species

Native species
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Species that normally live and thrive in a
particular ecosystem
Non-native (exotic or alien) species
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Species that migrate into an ecosystem or
are deliberately or accidentally introduced
into an ecosystem
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Cane toads
Indicator Species

Species that serve as early warning of
damage to a community or an
ecosystem (most sensitive)
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Birds
Fish
Amphibians
Indicators of thing like . . .
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Adult frog
(3 years)
Tadpole
develops
Into frog
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Young frog
sperm
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Sexual
reproduction
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Fertilized egg
development
Tadpole
Egg hatches
Eggs
Organ formation
Habitat loss
Drought
Pollution
UV radiation
Parasitism
Over-hunting
Diseases
Immigration or
introduction of
predators or
competitors
Keystone Species

Species that play roles affecting many other
organisms in an ecosystem
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Strong interaction with other species affect health
and survival of species
Process material out of proportion to their numbers
or biomass
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Pollination
Seed dispersion
Habitat modification
Predation by top carnivores
Recycling of plant and animal waste
Species Interactions
 competition
 predation
 parasitism
 mutualism
 commensalism
Competition

Intraspecific competition – competition
between members of the same species

Gain a competitive advantage (Plants)
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Chemical inhibitors
Seed dispersal
Territoriality (Animals)
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Patrol or mark an area
Defend an area
Competition

Interspecific competition – competition
between members of two or more
different species
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Abundant commonly used resources (food,
sunlight, water, soil nutrients, space, nesting
sites)
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Fundamental niche
Limited resources

Overlap of fundamental niches
Competitive Exclusion Principle

The niches of two species cannot
overlap completely or significantly for
very long.
Number of individuals
© 2004 Brooks/Cole – Thomson Learning
Resource Partitioning
Species 1
Species 2
Region
of
niche overlap
Number of individuals
Resource use
Niche Specialization
Species 1
Species 2
Resource use
Resource Partitioning
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Each species minimizes
competition with the
others for food by
spending at least half its
feeding time in a distinct
portion of the spruce tree
and by consuming
somewhat different insect
species.
Predator – Prey Relationship

Predation – members of one species
(predator) feed directly on all or part of a
living organism of another species (prey).

Benefits from reducing prey population
 Gives remaining prey greater access to
food supply
 Can improve the genetic stocks of the
prey population
Predator Tactics
Pursuit
Cheetah
Eagle
Wolves
Ambush
Preying Mantis
Snowy Owls
Humans