Chapter 54 - Chapter 54 A biological community is a group...

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Chapter 54 •A biological community is a group of populations of different species living close enough to interact. •Concept 54.1: Community interactions are classified by whether they help, harm, or have no effect on the species involved •Ecologists call relationships between species in a community interspecific interactions •Examples are competition, predation, herbivory, and symbiosis (including mutualism, paratism, and commensalism. •Interspecific interactions can affect the survival and reproduction of each species, and the effects can be summarized as positive (+), negative (–), or no effect (0) •Competition Interspecific competition (–/– interaction) is an interaction that occurs when individuals of different species complete for a resource that limits their growth and survival. Competitive Exclusion •Strong competition can lead to competitive exclusion , a local elimination of the inferior competitor. •The competitive exclusion principle states that two species competing for the same limiting resources cannot coexist in the same place Ecological Niches •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 Resource partitioning – the differentiation of niches that enables similar species to coexist in a community. •As a result of competition, a species’ fundamental niche, the niche potentially occupied by that species may differ from its realized niche, which is actually being occupied. Character Displacement Character displacement – the tendency for characteristics to diverge more 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) – one species, the predator, kills and eats the other, the prey •Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison •Prey display various defensive adaptations •Behavioral defenses include hiding, fleeting, or forming herds or schools •Animals also have morphological and physiological defense adaptations Cryptic coloration , or camouflage, makes the prey difficult to spot. •Animals with effective chemical defense often exhibit bright warning coloration, called aposematic coloration. •Predators are particularly cautious in dealing with prey that display such coloration
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•In some cases, a prey species may gain significant protection by mimicking the appearance of another species •In Batesian mimicry , a palatable or harmless species mimics an unpalatable or harmful model. •In
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This note was uploaded on 01/25/2011 for the course BIO 1510 taught by Professor Unknown during the Spring '07 term at Georgia Institute of Technology.

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Chapter 54 - Chapter 54 A biological community is a group...

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