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