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Chapter 4 Speciation and Phylogeny Outline and Review

Chapter 4 Speciation and Phylogeny Outline and Review -...

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Chapter 4 Speciation and phylogeny out and review 1. What Are Species? 1. Organisms that belong to a species are generally distinct from the members of other species. 2. Species are real biological categories, but some dissent exists in the true definition. 3. Biological Species The biological species concept defines a species as a group of organisms that interbreed. Reproductive isolation states that members of one group cannot successfully breed with members outside the group. The ability to breed leads to gene flow in the population. 4. Ecological species The ecological species concept emphasizes natural selection as a key force in creating and maintaining the species. Asexual species, in which gene flow does not occur, cannot be thought of as reproductively isolated. Selection would favor organisms of the same morphology, which would maintain their similarity even without gene flow. 2. The Origin of Species 5. Allopatric speciation When a population is divided by a barrier, different parts of the population adapt to different environments. The longer the groups remain isolated, the greater the genetic difference is between the groups. When the separation results in complete reproductive isolation, a new species is formed. Character displacement refers to an occurrence after the two separated groups come together. If there is some gene flow, such as through hybrid individuals, the competition between the groups over food or mates can still result in a divergence of characters. Reinforcement reduces gene flow between two formerly separated populations by selecting favorable adaptations that prevent mating between the members of the two populations. Allopatric speciation thus requires a physical barrier that interrupts gene flow and allows the two populations to diverge by means of natural selection. 6. Parapatric and sympatric speciation Parapatric speciation states that a new species can be formed if selection is combined with partial genetic isolation. At habitat boundaries, a hybrid zone can be formed. Sympatric speciation states that speciation can occur even in the absence of a physical barrier. Adaptive radiation occurs when a single species diversifies to fill numerous ecological niches. 3. Tree of Life 7. Carolus Linnaeus created a standard scientific taxonomy system in 1735, including the binomial nomenclature to distinguish all species. 8. A phylogeny is a family tree that shows the common ancestor of two or more species. 4. Why Reconstruct Phylogenies? 9. To classify and identify organisms.
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10. To understand why an organism evolved a particular trait. 11. To understand morphology and behavior.
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