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Speciation160-page8 - or even within the same area if...

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Methods of Speciation - 8 Hybrid Sterility: Successful mating and hybrid survival occasionally occur, but the offspring are sterile, since they lack homologous chromosomes essential for meiosis. The offspring may also appropriate mating signals (behavioral or morphological). The mule hybrid between the horse and donkey is a common example. Horse Mule Donkey Evolution – The Big Picture - Genetic Models and Rates of Speciation How does all of this go together to give a model or models for evolution? As we have seen and read, the process of evolution needs the presence of inheritable variation, and variations that can be beneficial within one's immediate surroundings. Adaptations of value in one habitat may be quite negative in others,
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Unformatted text preview: or even within the same area if conditions change. It is reasonably easy to determine speciation characteristics associated with changes that occur through time. When fossils from one era are compared to fossils from distant eras, they can be very different. When these differences appear significant, the extremes are called different species. The term, phyletic speciation or anagenesis is used for a species that evolves into a new, different, species through time. Anagenesis is associated with directional selection. When new species arise from branches that diverge from an original species, we use the term cladogenesis. Cladogenesis is associated with divergent selection....
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