25 Prezygotic is a barrier preventing a zygote from being formed while

25 prezygotic is a barrier preventing a zygote from

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25.) Prezygotic is a barrier preventing a zygote from being formed, while postzygotic barriers are in effect after the zygote is formed. 26.) A hybrid zone is a region in which members of a different species meet and mate. 27.) Fossils of certain species would sometimes show novel morphologies early on but later on don’t change much at all. Chapter 23 28.) Radiometric dating is a technique for dating fossils based on the decay of radioactive isotopes. Each isotope has a half-life, or the time required for 50% of the parent isotope to decay. 29.) The geologic record is the standard time scale which divides Earth’s history into four eons and other subdivisions. 30.) The layered rocks that form over time are known as stromatolites. The oldest fossils are from about 3,500 million years ago. 31.) Plate Tectonics describes the way that the continents “float” on the hot underlying portion of the mantle. 32.) A mass extinction is an event in which large numbers of species become extinct worldwide; there have been five mass extinction events in Earth’s history. 33.) Mass extinctions can reduce a thriving ecological community to nothing, as well as alter ecological communities. 34.) With mass extinction destroying ecological communities, there are many niches and roles left open by the newly extinct species. Adaptive radiation occurs since many new species are formed to fill these niches. 35.) Mutations in gene sequences and gene regulation can lead to speciation.
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  • Fall '17
  • Randy Smith
  • Evolution, Sasha Preston

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