Demographic stochasticity random variations in birth

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Demographic Stochasticity- random variations in birth and death rates in a population from year to yearEnvironmental Stochasiticity- changes in birth or death rates due to random variations in the environment
Genetic Stochasticity- changes in birth or death rates due to genetic variationsuch as genetic drift and inbreeding (both have greater impact on smaller populations)Competitive exclusion principle; conditions that allow competitive coexistenceCompetitive Exclusion Principle- two species use a limiting resource in the same way cannot coexist indefinitelyCompetitive coexistence can occur if species use different microhabitats, use different parts of a resource, use different size ranges of resources, respond to environment in different ways, or use resources at different timesRealized vs. fundamental nicheFundamental niche- the range of conditions and resources to which a species is adaptedRealized niche- he portion of the fundamental niche that a species actually exploits in the presence of competitors, predators, and parasitesHow to test for competition with experimentsTo test for competition you should compare species alone and with other species in a similar environmentResource partitioning, character displacementResource partitioning- when species use resources in different ways and allows them to coexistCharacter Displacement- Divergence in characteristics of two similar species where their ranges overlap as a consequence of selection for reduced interspecific competitionPredation-prey interactions – patterns they produce in population dynamics, factors that stabilize these interactions; functional responses ofpredatorsIf the predator isocline is more to the right than it is at a stable equilibrium and this also means the predator is relatively inefficient (low c and/or b)If predator isocline is more to the left than it is unstable and the predator will eventually die out and this also means the predator is highly efficient (high c and/or b)If prey has a refuge at lower population sizes then the graph will dip down at first then go back up when the population of prey increases.Factors stabilizing the interactions are:oDensity dependence in prey (or predator) population growthoDecreased efficiency of predator (due to evolution of prey defenses or environmental characteristicsoIncorporating type 3 functional responsePrey have physical refuge at low densityPredator cannot form search image when prey are at low densityPredators have alternative prey or switch when prey is rareMain types of plant defenses

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