Chapter 27: Community Interactions Community: all of the interacting populations within an ecosystem - A community encompasses the entire The most important community interactions include:1. Competition 2. Predation 3. Parasitism 4. Mutualism Ecological niche: the role of a particular species within an ecosystem - Habitat - Physical & environmental needs o Temperature o pH of soil o Amount of sunlight - What it eats - Competition with other individuals Competitive exclusion principle: no two species inhabit exactly the same ecological niche for an extended amount of time - One will outcompete the other Resource partitioning: when species with similar ecological niches coexist and compete they tend to occupy a smaller niche - Serves to minimize competition Interspecific Competition: can reduce population size and distribution Intraspecific Competition: major factor in controlling population size - Density dependent environmental resistance Predator/Prey Interactions- A predator eats other organisms o Includes both herbivores and carnivores o Each exerts selective pressure on the other often resulting in coevolution- Counteracting behaviors o Example: bats and moths o Bats hunt with sonar o Some moths are sensitive to the sonar and take evasive action if they detect it o Some moths emit clicks to confuse the bats - Camouflage conceals both predators and their prey o Blend in o Resemble something else - Some organisms mimic others o Mullerian mimicry: different distasteful species mimic each other o Batesian mimicry: harmless species mimic venomous ones o Startle coloration: patterns of color that resemble the eyes of a much larger animalo Prey can resemble their predators o Aggressive mimicry: predators resemble something attractive to their prey Mutualism: refers to interactions where both species involved benefit - Lichen o Fungus provides support o Photosynthetic algae supplies food - Clownfish and anemone o Anemone provides protection o Clownfish provides food Succession: a structural change in a community and its nonliving environment over time - Usually set in motion by some sort of disturbance - Starts with hardly plants called pioneers - Progresses to a relatively stable climax community There are two major forms of succession 1. Primary: a community forms where there is no trace of a previous community 2. Secondary: a new community forms after a disturbance that leaves part of the previous community
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