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Bio 322_take home final

Bio 322_take home final - Biology 322 Professor Hogue 1 It...

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Biology 322 Professor Hogue 12/5/07 1. It is not accurate to believe the first two humans, animals, or insects appeared in the same area during the same time frame and chose to reproduce. Species evolve from a single common ancestor or a few due to many factors. They do not come into existence independently. Speciation is the process by which new biological species arise. Speciation begins when gene flow is disrupted and populations become genetically isolated. The most common model of speciation is the allopatric speciation model, which occurs when two populations of a given species are separated by a geographical barrier such as a mountain range, a river, or an ocean. It also may occur if individuals of a given population manage to cross bodies of water, finding themselves on other islands. Isolation by means of geographical barriers produces reproductive isolation, resulting in genetic isolation. Sympatric speciation is the divergence of many species from a parental species inhabiting the same geographic region. It may occur if new ecological niches or new food sources become available. Polyploidy is a mechanism attributed to some sympatry events. It is due to changes in number of chromosomes and is commonly observed in plants. There are many mechanisms that create the conditions for speciation to occur. In some cases, species exist for long periods of time gradually changing in response to changes in their environment. Natural selection can cause populations to diverge based on food preferences or habitat choices. The theory of Natural Selection formulated independently by Charles Darwin and Alfred Russel Wallace, is based on the premise that individuals within a population vary; they exhibit different traits or characteristics.
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