2005_campbl53 - Chapter 53: Community Ecology Community...

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1 Chapter 53: Community Ecology Community Ecology ± A community consists of all of the organisms living within a certain geographical area ± These organisms include conspecifics as well as members of other species ± These organisms interact with each other both directly and indirectly ± Numerous (pessimists might say "endless") parameters affect what species are present and in what abundance ± "Simple generalizations can rarely explain why certain species commonly occur together in communities.“ ± "The distributions of most populations in communities are probably affected to some extent by both abiotic gradients and interactions [with other species]." Interspecific Interactions A key distinction between intraspecific and interspecific interactions is that the former but not the latter share a gene pool Intraspecific interactions do not generally lead to the extinction of a species; In interspecific interactions, losers can go extinct Commensalism The Knifes Edge! For the “host” species to be truly not affected by the commensal, either negatively or positively, is probably somewhat rare Interspecific Interactions Mutualism “The ants feed on sugar produced by nectaries on the tree and on protein-rich swellings (orange in the photograph) at the tips of the leaflet. The acacia benefits because the pugnacious ants, which attach anything that touches the tree, remove fungal spores and other debris and clip vegetation that grows to close to the acacia.” p. 1164, Campbell & Reece (2005)
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2 Mutualism “…the fish is able to produce a special mucus that causes the anemone not to release its stings… In return for the anemone's protection, the fish brings scraps to it, and lures larger fish into the anemone's tentacles.” http://mangrove.nus.edu.sg/pub/seashore/text/265.htm Interspecific Interactions One individual killing another One individual partly consuming another (especially a plant) A symbiont replicating at the expense of a host’s health + / - = more than just predation Defense against + / or + / –– ± Secondary compounds (plants) ± Nutritional deficiencies (plants) ± Mechanical defenses (plants) ± Production of poisons (animals) ± Mechanical defenses (animals) ± ± Fighting back (mostly animals) ± Cryptic coloration (mostly animals) ± Batesian mimicry (animals) ± Müllerian mimicry (animals) ± Immune systems (animals) Plant Defenses It is important to keep in mind that herbivores can be big (cows) as well as small (insects, fungi, bacteria), so more than one defense is typically necessary to defeat all possible predators Plants tend to be eaten in pieces rather than as a whole organism, so anything a plant can do to spare part of the plant from being eaten can also be advantageous Typically a plant will not manage to achieve complete avoidance of predation, but instead will limit their own predation to those organisms that possess appropriate morphological or biochemical adaptations
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This note was uploaded on 12/07/2011 for the course BIO 113 taught by Professor Staff during the Fall '09 term at Rutgers.

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2005_campbl53 - Chapter 53: Community Ecology Community...

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