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Answers_to_practice_final

Answers_to_practice_final - PRACTICE QUESTIONS ON LECTURES...

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PRACTICE QUESTIONS ON LECTURES 19 – 25 FOR FINAL EXAM Correction on Reading from textbook: For lecture 22, I asked you to read pp. 419-459 in Ch. 19 (along with other sections). This should have read pp. pp. 449 -459. 1. Define the biological species concept (BSC) and identify two of its limitations (i.e., instances where it doesn’t “fit” very well) BSC:Groups of actually or potentially interbreeding populations that are reproductive isolated from other such groups. Doesn’t deal well with asexual species or with species that interbreed to a limited extent (have hybrid zones. 2. How do the biological species concept and phylogenetic species concept differ? The phylogenetic species concept characterizes species as the smallest aggregations of populations that share a unique set of characters. Depending on the character set chosen, phylogenetic species could encompass more than one biological species (or vice versa). 3. Why are barriers to gene exchange important to speciation? Gene flow prevents genetic divergence between populations (is equivalent to interbreeding). Divergence is essential to all species concepts. 4. What is the difference between an extrinsic and intrinsic barrier? Give an example of both. An extrinsic barrier is one that does not pertain specifically to an organism, e.g., mountain range, ocean. An intrinsic barrier is internal to the organism, e.g. flowering time, genetic incompatability. 5. Know the difference between prezygotic (both pre-mating and post-mating) and postzygotic barrier and examples. See definitions and examples in lecture 6. Why is the spatial context of speciation important? The geographic context (allopatric, parapatric, sympatric) is important because it influences the potential for gene flow between populations. 7. In order for speciation to occur, in what geographic context(s) must natural selection be an important factor in divergence of lineages? Natural selection is important in parapatric and, especially, sympatric speciation. These are the contexts in which gene flow is likely and natural selection can cause divergence in the face of gene flow.
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