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Ecosystems & Living Organisms: Interactions and
Niches
Biological Communities
• Lack defined boundaries orgs never isolated
• Intrxns. lead to creation of ecological niches- Each org. has a role in an ecosystem.
Competitive Exclusion
• Two species with similar requirements cannot occupy the
same niche (Gause’s Law)
P. aureliaP. caudatum
Logistic Growth
Keystone Species
• Key members of community– Critical elements
– NOT always most abundant– ALWAYS most important
• KEY to conservation efforts
What is Predation?• Members of a predator species prey on members of a prey species
Stephen Colbert: Snakes and Hamsters
• http://www.comedycentral.com/motherload/index.jhtml?ml_video=58446
• http://www.comedycentral.com/motherload/index.jhtml?ml_video=58446
• http://www.colbertnation.com/the-colbert-report-videos/58446/january-31-2006/craziest-f--king-thing-i-ve-ever-heard---snake-and-hamster
Structural • Natural Weapons: Fangs, claws • Flexible bodies and Larger Size
Predator Strategies
Sharp Talons!!
• Ambush Techniques: Stalk a victim, Gape &
Suck (fish), Keen eyesight, Venom
Predator Strategies
Prey Strategies
Defense Techniques: Inflate, Flee, Fight Back, Stab, Poison
Structural advantages: Hard Body, Thorns/Spines, Break away body parts, Nat. Weapons
Prey Strategies
Predation Feedback Systems• Positive feedback (outcome is +) for predator
• gets to eat prey, can reproduce…• Negative feedback (outcome is -) =
• prey population falls, no food, decrease in predator population
Mimicry• Batesian mimicry: a
harmless species looks like a harmful species
• Mullerian mimicry: 2 harmful species look like each other
Scarlet King Snake
Coral Snake
Cuckoo Bee
Yellow jacket
Interactions Among Organisms
Symbiosis: relationship b/t 2
species
•Mutualism (+,+)
•Commensalism (+,0)
•Parasitism (+,-)
Mutualism
• Both Species Benefit
• Rhinos and oxpeckers
Mycorrhizae• Symbiotic fungus found on plant roots
• Aids in water retention, mineral uptake (nitrates)
W/out M With M
Commensalism
• One member is helped, the other neither benefits or is harmed
• Cows and Cattle Egrets
Parasitism• + and -
relationship• parasite benefits,
host loses• parasite usually
smaller than hostLeech Bite, Thailand
Lamprey
Endoparasites• Parasites that live within the body of the
host!• Ex. Tapeworm…
Ectoparasites
• Parasites that feed on the external surface of the host.
• Ex: ticks
Intraspecific Competition
• Between SAME species
Interspecific Competition• Competition between
DIFFERENT species
Intra or Interspecific Competition??
• http://www.youtube.com/watch?v=Tt6C6P3bJq8