Population Interactions
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Ecosystems are made of many populations
living together
How do populations live together?
◦ 5 types community interactions
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Competition
Mutualism
Commensalism
Parasitism
Predation
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Organisms compete for same resources
(food, space, etc)
Nature doesn’t like competition
◦ Reduced through species occupy different
NICHES – the physical and biological
conditions
 Include:
 Food types
 Predators
 Temperature needed to survive
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An interaction in which organisms of both
species benefits

+/+ relationship
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In other words: Let’s work together!
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Example: Bees and flowering plants
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An interaction in which one organism
benefits (the commensal) and the other
organism has no benefit or harm (the host)
+/0 relationship
In other words: I don’t care what you do as
long as it doesn’t affect me.
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Example: Clownfish
and sea anemone
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An interaction in which one organism
benefits (the parasite) and the other
organism is harmed (the host)
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+/- relationship
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In other words: I’m stealing from you!
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Example: Ticks and Dogs
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1.
2.
3.
Predation and parasitism are both +/interactions, but there are several
differences
The parasite is often much smaller than the host.
The parasite consumes only a small amount of
the host at a time. Predators will eat most of their
prey
Parasite can use host for other (protection,
reproduction, etc). Predation only for food
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http://www.youtube.com/watch?v=63UAB4J2
r7Y
Hookworms
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Strangler Fig
Zebra Mussel
Tongue
Eating
Louse