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Unformatted text preview: Community Ecology: Chapter 54 • A biological community is an assemblage of populations of various species living close enough for potential interaction • Ecologists call relationships between species in a community interspecific interactions • Examples are competition, predation, herbivory, and symbiosis • Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0) • Interspecific competition (–/– interaction) occurs when species comppete for a resource in short supply • Can occur between similar species (different plant species in a garden competing for soil nutrients) or very different species (grasshoppers and bison competing for resources) • Strong competition can lead to competitive exclusion , local elimination of a competing species • The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place • The total of a species’ use of biotic and abiotic resources is called the species’ ecological niche • An ecological niche can also be thought of as an organism’s ecological role • Ecologically similar species can coexist in a community if there are one or more significant differences in their niches • Character displacement is a tendancy for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species • An example is variation in beak size between populations of two species of Galápagos finches • Predation (+/– interaction) refers to interaction where one species, the predator, kills and eats the other • Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison • Prey display various defensive adaptations • Behavioral defenses include hiding, fleeing, forming herds or schools, self defense, and alarm calls • Animals also have morphological and physiological defense adaptations • Cryptic coloration , or camouflage, makes prey difficult to spot •...
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- Spring '07
- Ecology, Glacier Bay, species Species diversity