Chapter 47- Community Ecology

47.1 Concept of Community

Community = assemblage of populations interacting with one another
Example: squirrel, moose, bear, fox, wolf, pine tree, termites, bacteria....etc

Composition: what organisms live there | Diversity: abundance of different species (biodiversity)

47.2 Structure of Community

Habitat = particular place an organism lives

Ecological Niche: the role it plays in the community (includes food sources, reproduction, placement)

Fundamental Niche - all the conditions that an organism can survive
Realized niche - where it actually exists in nature

Interspecific Competition: competition between different species

Competitive Exclusion Principle - no two species can occupy the same niche

Resource Partitioning - species with niche overlap, share/partition resources (see balanus), P. caudatum dies out as a result of competition

Generalist - eat different things, live in a variety of spaces (raccoon) | Specialist - very specific needs (panda)

Character Displacement – can result in changes to the morphology of a species as a result of resource partitioning (beak size in finches)

Predator - Prey Interactions

predator prey graph

Prey Defenses

Camouflage (cryptic coloration) - blending in
Mimicry - one species resembles another as a defense (milk snake)

Herding Behavior (zebra)
Startle Behavior (blowfish)
Anatomical defense (porcupine)
Chemical defense (skunk)

Symbiotic relationships

Symbiosis - intimate relationship between two or more species

Parasitism - one individual is harmed, the other benefits (ticks & deer)
Mutualism - both benefit (flowers & honeybees)
Commensalism - one benefits, other is neither harmed or benefited (clown fish & sea anemone)

47.3 Community Development

Ecological Succession - involves a series of species replacements

Primary Succession - occurs where there is no soil formation (volcanic island)
Secondary Succession - occurs after an area is disturbed (prairie fire)

Pioneer Species - first species to inhabit an area
Climax Community - when the species replacement slows and the ecosystem stabilizes

47.4 Community Biodiversity

Intermediate Disturbance Hypothesis - moderate disturbances in an ecosystem are necessary to maintain biodiversity

Keystone Species - needed to maintain biodiversity (often top predators)

Ex: Kelp, Sea otters, Sea urchins, Abalone - what happens when you remove the otters

Exotic Species - a species introduced into a habitat, often causes major disturbance and even extinction of native species

Ex: Kudzu, Snakehead catfish, Piranha, Mussels