Community Ecology

Big Idea 4: Biological Systems Interact

ECOLOGY• Study of

living organisms and their interactions with the non/ living environment

Who Lives Where?

• Orgs adapted to a specific set environmental conditions, through evolution (natural selection)

Peppered Moths of England

• Dispersal: Movement of species from areas of high pop. density to low.

• Can be caused by:1. Species expanded

range naturally 2. Species was

transplanted Great tailed grackle: Moved north to Gulf of Mexico

Who Lives Where?

• Abiotic and Biotic Factors are Limiting!!

• Abiotic: temp., H2O, sun, wind, soil, climate.

• Biotic: animals, plants, bacteria

Ex: Tidepools in Intertidal Zones, Must withstand exposure to sun at

low tide.

Who Lives Where?

Biological Communities

• An area where different pops interact w/ each other w/ no boundaries

• Leads to creation of ecological niches- a role in an ecosystem (fills a niche).

What’s My

Niche?

Communities Have Competition…

• Interspecific Competition: occurs b/t diff. species.

• Due to resources in short supply.

Intraspecific Competition

Intra or Interspecific Competition?

Competitive Exclusion

• 2 species cannot coexist in a community if their niches are identical. (Gause’s Law)

Paramecium caudatum Paramecium aurelia

Gause’s Experiment

Logistic Growth

When Niches are the Same…• Species can

evolve to coexist

• Resource partitioning- a

species changes

behavior so it can coexist w/ a similar species.

Resource Partitioning

Keystone Species

• Key members of community– Critical elements

– NOT always most abundant– ALWAYS most important

• KEY to conservation efforts

Predation in Communities

• Members of a predator species prey on members of a prey species

• Stalking, Keen eyes, Venom• Natural Weapons: Fangs, claws • Flexible bodies and Larger Size

Predator Strategies

Prey Strategies

Defense Techniques: Inflate, Flee, Fight Back, Stab, Poison

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

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

Herbivory

• Herbivore only eats a part of plant/alga.

• Plants may have chemicals to deter

Symbioses in Communities

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