Bio102-Chap3Notes

Bio102-Chap3Notes - Communities Species Interactions Themes...

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Communities & Species Interactions – Themes: 1. Species tolerances & adaptations Not community-level processes 2. Species interactions Predation, competition, symbiosis Ecological Niches 3. Community structure Vertical and horizontal patterns 4. Community dynamics Short-term variation & succession 1. Species Tolerances: a. Critical Environmental Factors (Organismal & Population Ecology) Limiting factor ( Von Liebig ) - the single factor in shortest supply limits the species growth Tolerance limits ( Shelford ) - each factor has both minimum and maximum levels, beyond which a species cannot survive For many species, the interaction of several factors determines biogeographical distribution (e.g., temperature & moisture) Species requirements and tolerances can also be used as Environmental Indicators Lichens (air pollutants) Trout ( low O 2 ) b. Adaptation vs. Acclimation Adaptation = inherited genetic traits allowing a species to live in a particular environment (population level trait) Results from evolution (natural-selection) Acclimation = range of physiological modifications possible for individual organisms (organismal trait) c. Evolution via Natural Selection Natural Selection - Members of a pop. best suited for particular environmental conditions survive and reproduce more successfully than their cohorts Limited resources and environmental stresses place “selective pressures” on a population Acts on existing genetic diversity in pop. Evolution —> Speciation 1) Natural selection —> differentiation within population —> new populations 2) Geogrphic or reproductive isolation of new population prevents genetic exchange —> new species 2. Communities: Species Interactions 3 main interactions: a. Predation b.
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