Chapter 24 BSC 114
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This 1 page Class Notes was uploaded by Rebecca Sharp on Saturday April 30, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 16 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 04/30/16
Evolutionary theory focuses on speciation, or the origin of new species. Evolution has to be able to explain how new species come about and how populations evolve. o Vocab; Microevolution; changes in allele frequency in a population over time o Vocab; Macroevolution; broad patterns of evolutionary change above the species level Biological Species Concept says that a species is a group of populations whose members can successfully interbreed and produce viable fertile offspring and not with other populations. It has a heavy insistence on reproductive isolation. o Limitations of the BSC; it cannot be applied to anything that does not sexually reproduce (ie fossils, asexual organisms, and all prokaryotes), it emphasizes the absence of gene flow even though gene flow can and does occur sometimes between distinct species (ie grolar bears, the offspring of polar bears and grizzlies) Speciation does, to a large degree, come from reproductive isolation. Reproductive isolation is the inability of two organisms to produce fertile viable offspring. It comes in two distinct varieties; o Prezygotic; cannot even do the sex to create any offspring. These are habitat isolation (when he lives across the mountains and you don’t have a car), temporal isolation (when she only wants it at night and you sleep at night), behavioral isolation (when he sags his pants and you’re intelligent), mechanical isolation (when you’re both different snails and your dirty parts just don’t line up right) and gamete isolation (when sperm of one species is not able to fertilize the eggs of another). o Postzygotic; can do the sex but something else prevents the offspring from being ok. These are reduced hybrid viability (when the hybrid is weaker than both parents and is thus always selected against), reduced hybrid fertility (mules), and hybrid breakdown (when the first generation is fine but down the generational line everything falls apart) Speciation can be allopatric or sympatric o Allopatric speciation is when the gene flow is interrupted or reduced when a population is geographically isolated and evolves over time o Sympatric speciation is when a subset of the population makes a new population on their own because of nonrandom mating or mutations. Speciation can happen all at once, or it can happen very slowly. When it’s slow, it’s called gradual speciation. When it happens all at once, it’s called punctual speciation. Polyploidy is the presence of extra sets of chromosomes due to accidents during cell division. It happens much more in plants than in animals. It can create entirely new species within a single generation. An autopolyploid is any individual with more than 2 sets of chromosomes from one species An allopolyploid is a species with multiple sets of chromosomes, but from different species.
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