Wednesday, October 24, 2007

Community Ecology: Part DUEX.

predation drives evolution:
basically - as predators become better at locating and subduing pray, their pray over time develops adaptations to elude and defend themselves. Pray can have adaptations such as horns, speed, muscle or coloration. Plants who are pray can develop spines, toxins or thorns.
There are many different types of defense mechanisms such as camouflage (cryptic coloration), Aposematic coloration, Batesian mimicry and Mullerian mimicry.

Cryptic coloration is when an organism's phenotype resembles or is even identical to its surroundings. This is used to make themselves harder to find by predators.

Aposematic coloration is another form of defense mechanisms. Aposematic means (in Ms.Foglia's terms) that an animal is saying " don't eat me , don't eat me." An organisms doesnt want to be eaten not only so they, obviously, survive and also because they are poisonus or just taste horrible. Most of the time animals have the colors black, red, orange and yellow to show predators that they shouldn't be eaten.

Batesian mimicry is when a creature is harmful and another animal that mimic's it is not harmful. The animal that is mimicing the harmful animal has an advantage because predators will stay away from it to not take a chance of getting sick or dying. An example is of the green parrot snake and the hawkmoth larvae. These two animals also have convergent evolution meaning they have the same solution to the same problem.

Mullerian mimicry is when all of the organisms that look the same are "nasty" ( meaning they're poisonus or taste bad). With this type of mimicry predators may evolve an innate avoidance of any animal or organism that looks like or is the harmful one.

Coevolution in Community:
there are three different types of coevolution in a community: Predator- prey relationships, Parasite-host relationships, and flower & pollinator relationship. This involves long term evolutionary adjustments between species.

characterizing a community:
every community has a structure made up of three diffferent parts: Species diversity ( how many different species are present, composition ( dominant or most abundant species, species with the largest biomass)( biomass is if you took an entire species and dried them out and weighed them), and a keystone species ( which plays a key role and has a strong effect on coposition of the community)

species diversity:
greater biodiverstiy offers more food resources, more habitat and more resilience in the face of enviornmental change.

keystone species:
they have an influential ecological role and can increase the diversity of a habitat.
keystone species can effect the community in two ways : they can increase nutrients from the bottom of the food chain up, or start at the top and can control herbavore devistation going down the food chain.

good night guys. hope this was helpfull!!!! oh and sherpa for tomorrow night is KIM!

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