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Ecosystems & Living Organisms: Interactions and Niches Biological Communities • Lack defined boundaries orgs never isolated • Intrxns. lead to creation of ecological nichesEach org. has a role in an ecosystem. Competitive Exclusion • Two species with similar requirements cannot occupy the same niche (Gause’s Law) P. caudatum P. aurelia 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.colbertnation.com/the-colbert-reporthttp://www.comedycentral.com/motherload videos/58446/january-31-2006/craziest-f--king-thing-i-ve/index.jhtml?ml_video=58446 ever-heard---snake-and-hamster Predator Strategies Structural • Natural Weapons: Fangs, claws • Flexible bodies and Larger Size Sharp Talons!! Predator Strategies • Ambush Techniques: Stalk a victim, Gape & Suck (fish), Keen eyesight, Venom Prey Strategies Defense Techniques: Inflate, Flee, Fight Back, Stab, Poison Prey Strategies Structural advantages: Hard Body, Thorns/Spines, Break away body parts, Nat. Weapons 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 Cuckoo Bee Yellow jacket Scarlet King Snake Coral Snake Interactions Among Organisms Symbiosis: relationship b/t 2 species •Mutualism (+,+) •Commensalism (+,0) •Parasitism (+,-) Mutualism • Both Species Benefit • Rhinos and oxpeckers • Symbiotic fungus found on plant roots • Aids in water retention, mineral uptake (nitrates) W/out M With M Mycorrhizae 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 host Leech 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=Tt6C6P 3bJq8