gen bio - lecture 24: community ecology

community

an association of populations that live and interact in the same place @ the same time

resource (+ limiting resource)

• resource: anything from the environment that meets the needs of a particular species

• limiting resource: a resource in scarce supply

habitat

location where a species lives it's life (its address)

ecological niche (vs. fundamental vs. realized)

• ecological niche: sum of a species’ use of biotic and abiotic resources + its profession within its habitat

• fundamental niche: niche potentially occupied by a species → BROAD

• realized niche: niche actually occupied by a species → MORE NARROW

competition OVERALL DEFINITION

• 2+ individuals attempt to use the same resource

  • use by one decreases availability for others

  • -/- interaction → both participants are hurt

• between SAME species = INTRAspecific competition

• between DIFF species = INTERspecific competition

• competition is considered the most important determinant of…

  • # of species in a community

  • size of each population

  **requires overlapping niches to operate

complete vs. partial niche overlap (+ competitive exclusion, extirpation, resource partitioning, character displacement)

• complete overlap:

  • 2 species with identical ecological niches CANNOT coexist bc compete for SAME limited resources

  • one wins, one loses

• partial overlap:

  • can coexist if there are non-overlapping parts of niches

    • competitive exclusion: selection in one competitor due to competition for a diff set of resources

• extirpation: going locally extinct due to competition

• resource partitioning: differentiation of niches that allows similar species to coexist

• character displacement: becoming better @ using specific resources to minimize competition

predation

one species, the predator, kills and eats prey (+ / - interaction)

coevolution

results in an evolutionary “arms race”

1. predator: evolves better prey-catching strategies

2. prey: evolves better predator avoidance

predator adaptations

claws, fangs, venom, speed, camouflage, mimicry

prey adaptations (2 types and examples)

• mechanical defense

  • aposematic coloration: warning coloration (ex. found in frogs that store poison under their skin)

• chemical defense

  • cryptic coloration: camouflage colors/markings that blend into the physical surroundings

batesian mimicry

a harmless species mimics a harmful one

müllerian mimicry

2 harmful species mimic each other (MORE of the same)

herbivory (plant predation)

an organism eats part of a plant or algae (+ / - interaction)

• plants cannot escape but have ADAPTATIONS to help lower chances of being eaten

  • physical: spines, thorns, thick and waxy coating

  • chemical: bad taste, toxicity

symbiosis (+ 3 types)

intimate, long term relationship

• parasitism: parasite benefits + host harmed (but rarely killed)

  • + / - interaction

• mutualism: BOTH benefit and depend on each other (ex. mitochondria in your cells; some fungi)

  • + / + interaction

• commensalism: one species benefits and the other is neither harmed/helped (ex. cattle egrets + african buffalo)

  • + / 0 interaction