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Chapter 52. Community Ecology. Ecological niche Distinctive lifestyle and role of an organism in a community Takes into account all abiotic and biotic aspects For example, an organism’s habitat is one parameter used to describe the niche. Connections to the size of the acorn crop.
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Chapter 52 Community Ecology
Ecological niche • Distinctive lifestyle and role of an organism in a community • Takes into account all abiotic and biotic aspects • For example, an organism’s habitat is one parameter used to describe the niche
Fundamental niche • Potential ecological niche for an organism • Realized niche • Niche an organism actually occupies • Limiting resources • Environmental factors that restrict a realized niche
Competition • Two or more individuals attempting to use the same resource • Intraspecific competition • Among individuals within a population • Interspecific competition • Between different species
Competitive exclusion principle • Two species cannot occupy the same niche in the same community for an indefinite period • One species is excluded by another as a result of competition
Some species reduce competition by resource partitioning • Competition among species is reduced by character displacement • Structural ecological and behavioral characteristics diverge where ranges overlap
Predation • Consumption of one species (the prey) by another (the predator) • Coevolution • Predator and prey both evolve more efficient ways to interact
Defenses • Mechanical defenses • Associating in groups • Cryptic coloration • Warning coloration • Müllerian mimicry
Symbiosis • Mutualism • Both partners benefit • Commensalism • One partner benefits and the other is unaffected • Parasitism • One partner benefits while the other is harmed
Keynote species • Present in small numbers but are crucial in determining the species composition and ecosystem functioning • Dominant species • Affect the community because they are so common
Species richness • Number of species within a community • Species diversity • Relative importance of each species within a community
Ecological succession • Primary succession • Occurs in an area not previously inhabited • Secondary succession • Occurs where there is a pre-existing community and well-formed soil
Intermediate disturbance hypothesis • Disturbance affects succession and species richness • Species richness is greatest at moderate levels of disturbance
The nature of communities • Organismic model • Views a community as a superorganism that goes through stages of development (succession) • Individualistic model • Abiotic environmental factors are primary determinants of species composition • Organisms are independent