Community Ecology

biological assemblage of populations of various species living and interacting at a given time and place

• role of an organism in an environment
• "profession"

• environment in which the organism lives 
• "address"

• Diversity
• Dominant Species
• Prevalent Form of Vegetation
• Stability
• Structure

variety of kinds of organisms

• species richness
• relative abundance

• Greatest abundance or biomass
• May not be the most important in maintaining overall stability

ability to return to original state when disturbed

• Predator (or herbivore), not often dominant
• Maintains community structure/diversity
• removal may be catastrophic
• keep species in check that might outcompete other species
• E.g. Starfish in relation to barnacles and mussels (muscles cannot survive with barnacles, starfish eat barnacles)

Various species will occupy different zones (like in tall trees)

• both species benefit (+/-)
• Eg: Intestinal bacteria in humans give Vitamin K while getting a stable environment

• one benefits, other no effect (+/0)
• E.g.: Follicle mites do no harm on human head, but have stable environment to live and reproduce

• one harmed (host), one benefits (parasite) (+/-)
• E.g.: Tapeworms

• (+/- and -)
• Predator = eater
• Prey = eatee
• Prey generally killed and eaten immediately
• E.g.: frog/fly

• chemical deterrents (poisons, tastes)
• physical deterrents (spines, thorns)
• mutualism (ant acacias)

• Speed 
• Vision, smell
• Chemicals (skunk)
• Mimicry
• Advertise with bright colors and be toxic

• (-/-)
• Detrimental to both species
• occurs when resource limited
• intensity of competition based on niche similarity

• Competitive Exclusion
• Competitive Equilibrium

One species drives the other to extinction

• Species co-exist
• Use non-overlapping parts of niches

based on species' suitable range of environmental conditions

Based on environmental factors