Transcript ENVI 30 Environmental Issues

I.
Community Ecology
A.
Competition
3.
Resource partitioning
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Competitive exclusion can be minimized if
competing species modify niches to reduce overlap
Usually involves dividing resource
Anolis
Dominican
Republic
Fig. 54.2
I.
Community Ecology
A.
Competition
4.
Character displacement
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Resource partitioning may lead to directional
selection on one or both species
Directional selection may lead to divergence in traits
Fig. 54.4
I.
Community Ecology
B.
Predation
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Involves consumption of prey by predator
Predator usually has adaptations to facilitate capture of
prey
Natural selection acts on both predator and prey
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1.
Coevolution
Strategies
a.
b.
c.
Pursuit predation
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Predators chase prey to capture them
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Predator usually faster, stronger, &/or more agile than
prey
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Some species hunt in groups
Ambush predation
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Predators lie in wait for prey
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Predators usually camouflaged or concealed
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May involve lures
Aggressive mimicry
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Ex: Bolas spider mimics odor of female moths to
attract male moths
I.
Community Ecology
B.
Predation
2.
Predator avoidance
a.
Escape
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Running/Swimming/Flying away
b. Mechanical defenses
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Ex: Porcupine quills, armadillo armor
c. Social behavior
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Ex: Schooling, standing watch
d. Chemical defenses
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Ex: Poison dart frog, skunk
e. Defensive coloration
Cryptic coloration
- Canyon tree frog
Aposematic coloration
- Poison dart frog
Müllerian mimicry
Batesian mimicry
Fig. 54.5
Batesian Mimicry
Sam Crothers
I.
Community Ecology
C.
Herbivory
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Consumption of plants by animals
Most herbivores are small
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Ex: Insects, snails/slugs
Herbivores adapted to consume plants
Some plants have anti-herbivore defenses
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Physical – Ex: Thorns, spines
Chemical – Ex: Nicotine in tobacco, pyrethrins in
chrysanthemums
Coevolution has affected herbivore evolution
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Ex: Monarch butterfly caterpillars can eat milkweed
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Toxic to most herbivores
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Nearly exclusive access to food source
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Can sequester noxious compounds for defense
I.
Community Ecology
D.
Parasitism
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Parasite benefits at expense of host
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Fig. 33.12
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Host harmed in process
Ex: Tapeworm absorbs nutrients from host digestive
system
Endoparasites – Live within body of host
Ectoparasites – Live outside body of host
Parasitoids – Lay eggs on/in host; larvae feed
on host, eventually killing host
Many parasites have complex life cycles
Fig. 33.11
Schistosoma mansoni
I.
Community Ecology
E.
Disease
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Widespread disease outbreaks may alter
community composition and dynamics
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Ex: Dutch elm disease
Ex: Sudden oak death
Ex: Avian flu
Ex: West Nile virus
I.
Community Ecology
F.
Mutualism
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Symbiotic relationship in which both partners
benefit
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Ex: Ants & acacia trees
Ex: Nitrogen fixing bacteria (Rhizobium) & legumes
Ex: Zooxanthellae & reef-building corals
Ex: Mycorrhizae & plants
Ex: Anemones & clownfish
I.
Community Ecology
G. Commensalism
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One organism benefits, other isn’t harmed or
helped
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Ex: Cattle egrets and cowbirds & ungulates (expose
insects while grazing)
Hard to document (both species usually
affected to some degree)
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Ex: Some commensal birds may remove ticks &
other ectoparasites from herbivores