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Lecture_13_Community_Ecology

Lecture_13_Community_Ecology - Ecology is studied at...

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6/15/2011 1 Community Ecology LS1: Summer Session A July 22, 2011 Ecology is studied at different levels Organismal Ecology Population Ecology Community Ecology Ecosystem Ecology Global Ecology Community A community is an assemblage of different species interacting in the same area Species interactions Antagonistic interactions : one species benefits, the other is harmed Predation Herbivory Parasitism Mutualisms : both interacting species benefit Competition : both interacting species are harmed Commensalism : one species benefits, the other is unaffected Amensalism : one species is harmed, the other is unaffected
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6/15/2011 2 Not all species relationships fit neatly into these categories Coevolution All types of species interactions can impact the evolution of the species involved Coevolution refers to the adaptation of features in a species in direct response to the actions of another species An evolutionary arms race Predator-prey interactions Predator-prey relationships lead to a wide array of adaptations Many predators are larger, stronger, and/or faster than their prey Prey defenses Camouflage, or crypsis , is an important defense for prey species Some species are disguised as objects that are inedible or unpalatable to predators, a phenomenon called homotypy Prey defenses Many prey species have evolved chemical defenses Species capable of defending themselves typically exhibit aposematic coloration , advertising their toxicity to potential predators Prey defenses Some prey species evolve to resemble organisms that are noxious in a condition known as mimicry Mimicry can occur in two ways: Batesian mimicry occurs when a non-toxic mimic evolves to resemble a toxic model Müllerian mimicry is when several aposematic species converge on a common pattern
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6/15/2011 3 Batesian mimicry Müllerian mimicry Herbivory The most widespread interspecific interaction on earth, herbivory involves organisms eating plants The most potent herbivores are the insects Herbivores can be either Oligophagous , specializing on one or a few plant species; or Polyphagous , generalist herbivores Typically, herbivores only feed on specific parts of plants, and do not kill them Plant defenses Chemical defenses: toxins Physical defenses: thorns, spines, silaceous cell walls Mimicry Parasitism Parasitism can lead to disease, and as such, many parasites (particularly microparasites) are considered pathogens Pathogenic parasites have complex evolutionary relationships with their hosts as host resistance and a pathogen’s virulence interact Ectoparasites Parasites can also be external, and coevolutionary relationships may also form between hosts and their ectoparasites
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