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Biology - Populations and Evolution

Gene pool is all the genes in a population of one particular species. Genetic variability is the fact that gene pools have lots of different alleles in them. Genetic variability arises through the process of random mutation.

Evolution can be summarized in the following three statements:
  1. Due to ongoing random mutation, there is always, within a species population, genetic variability. So, there are lots of different genes running around in the gene pool.
  2. At some time or other, for some reason or other, some portion of the population finds itself in a new environment. In the new environment, one of the genes that is running around in the gene pool confers an advantage on the individuals who happen to have it. Those individuals survive and reproduce in greater numbers than do the individuals without that particular gene. The population in the new environment has a gene pool that is different from the population in the old environment.
  3. Speciation just means the creation of a new species. Speciation results from prolonged evolution. If two populations evolve separately for a long time, they will ultimately be so different from one another that they would not be able to interbreed anymore. When a mutation allows one individual to take advantage of its environment in some new way and, thus, to minimize competition with other individuals, it is called adaptive radiation. Adaptive radiation produces new species.

Make sure you know which of these terms describes what process. Speciation means that over a long period of time and under certain conditions, a new species can develop. Adaptive radiation means that a new species can arise from the parent species by adapting to a different ecological niche. The Hardy-Weinberg Law says that in a large population, the gene pool tends to remain stable generation after generation. Genetic drift means that in a small population, the gene frequency drifts randomly.

Species are identified according to this scheme: kingdom, phylum, class, order, family, genus and species. Here is an easy way to remember all that, “King Philip Came Over From Germany. So?”

The following is all you need to know about comparative anatomy. Chordates are a phylum that includes invertebrates and vertebrates. You should know that chordates are noted for having three things: a dorsal nerve cord, gill slits and a notochord. Vertebrates are noted for having four things: vertebral column, closed circulatory system, developed nervous system and developed sensory apparatus.

Symbiosis is about two organisms that live together in very close association. The word symbiosis does not tell you what is going on between the two organisms. They may be hurting each other, or they may be helping each other. Symbiosis just means that two organisms live together in close association.

Mutualism is when two organisms of different species live in close association and somehow help each other out.

Commensalism is when one organism benefits from another and the other organism gets no benefit and suffers no harm.

Parasitism is when one organism feeds off another and does cause harm to the other.