lizzie3622biol121c24 Elizabeth A. Morrison
  Biol121
 
Chapter 24: Communities and interactions between organisms.
I.Introduction
 A.Communities are made up of all living things in a given area. Sometimes recognized by distinctive species
 B.All organisms are linked, depend on other organisms.
 C.Benefit, harm in relationship. Benefit and hurt each other
 D.Ecological niche the way that organism interacts with its environment
   1.The habitat (where organism lives), role and requirements for environmental resources and tolerance ranges for each abiotic factor. Affected by almost all traits of organism.
   2.Potential or fundamental niche: full range of possible role/conditions with no interference.
   3.Realized niche: limited by competition with other species, isolation  (has to be able to get there). Narrow vs. Broad: orchids (may only be able to be pollinated only by one species, so they can only grow where that species lives), humans, sensitivity to extinction. Endemic: present in very narrow ranges, like orchids.
    4.Niche overlap competition for a resource. If a species just isn't as good -- they must coexist or exclude.
 E.Coevolution: evolutionary change in one organism creates selective pressure favoring an evolutionary response in another. A factor in the evolution of almost all organisms that interact with each other. Organisms need not be related to each other.
II.Competition: harms both organisms. Result of overlapping niches, and always bad for everyone in the short term.
 A.Intraspecific (within: natural selection) or interspecific (not within own species)
 B.Exploitative competition is indirect: two species use the same resource. If it is scarce, success will depend on efficiency of use. They don't block, it simply depends on who eats/uses it faster.
 C.Interference competition is direct: one species prevents the other from using a resource: territoriality. Active competition: not depending on scarcity.
 D.Competitive exclusion winner takes all. Identical niches. Paramecium experiments: a. Sigmiod, b. Sigmiod with more rapid growth, a+b. B continues, while a eventually falls back.
   1.May not happen if resource is abundant, environmental conditions change frequently, long term process. If a is cool and b is warm, and if the temperature changes frequently, neither will be favored.
   2.An alternative to competitive exclusion: evolutionary change that allows both species to survive.
     a.Mild change: resource partitioning: warblers. Guilds = similar niches, same species.
     b.Radical change: character displacement: Galapagos finches. They no longer use the same resources, and their critical character completely changed.
     c.Ecological equivalents do not overlap because habitats are different. Not in the same place at the same time.
III.Symbiosis: a long term, close association. These relationships are most often, but not always symbiotic:
 A.Commensalism: interactions that benefit one organism and are neutral to other. Bird nests, epiphytes (plants that live on other plants -- Spanish moss). Intergrades with both parasitism and mutualism.
 B.Mutualism interactions that benefit both. Often symbiotic.
   1.Essential to survival of both: termites and protozoa. Termites can't digest wood, but the organisms that live in their digestive systems, protozoa, do.
   2.May be noncompulsory: ants and acacias, lichen: fungus + algae. Both are helped, but not needed.
   3.Endosymbiotic theory. Mitochondria and chloroplast. Inside cells are smaller organisms that are actually bacteria, which have their own DNA.
 C.Parasitism: a  parasite lives on or in the host. The host usually survives. One benefits, the other is hurt. Always symbiotic. Host can usually survive one attack by one parasite.
   1.Includes diseases
   2.If a single parasite kills the host, it is a parasitoid. Rare. Wasps and caterpillars, larvae of wasp consumes caterpillar from inside out.
   3.Host specific, highly specialized, many cannot survive without host. Host is trying to get rid, so they must be very adaptive to survive; result of coevolution.
   4.Brood (social) parasitism: cowbirds.
IV.Predidation and herbivory:
 A.Interactions that harm one organism and benefit the other, one species serves as a resource for another.
   1.In predation the predator eats the prey
   2.If the prey is a producer, the predatory is a herbivore.
   3.Carnivores eat animals, omnivores both.
 B.Plant adaptations
   1.Morphological defenses: thorns, hairs. Morph = "form." Visible.
   2.Secondary compounds: poisons. May only be made when needed.
   3.Coevolution: herbivores must be able to overcome existing defenses and develop new methods to overcome new defenses. Link between coevolution and speciation
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Biol121, Fall 2000.... chapter 24
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