4.2-Niches & Community Interactions -Niche-range of physical & biological conditions in which a species lives & the way the species gets what it needs to survive & reproduce ~environment it lives in ~how it interacts with biotic & abiotic factors ~resource-what you need to live—water, nutrients, food, space

Tolerance-ability to survive & reproduce under a range of environmental circumstances (every species has some level of tolerance) Physical Aspects-abiotic factors needed for survival Biological Aspects-biotic factors needed for survival

Competition-when organisms attempt to use the same limited ecological resource in the same place at the same time Intraspecific competition-same species Interspecific competition-different species **In competition, there is always a winner (lives) & a loser (dies)

Competitive Exclusion Principle No two species can occupy exactly the same niche in exactly the same habitat at the same time. Predation-interaction where one animal (predator) captures & feeds on another animal (prey) Herbivory-interaction where one animal (herbivore) feeds on producers (plants)

Keystone species-changes in the population of a single species that can cause dramatic changes in the structure of a community. symbiosis-”living together”--any relationship where two species live closely together.

3 main classes: 1. mutualism-a relationship where both species benefit (sea anemone & clownfish) 2. parasitism-relationship where an organism lives inside or on another organism & harms it (tapeworm) parasite 3. commensalism-relationship where one organism benefits & the other is not helped or harmed (barnacles on whale's skin)