EEB318H1 Final: EEB318 Final Exam Study Questions and Answers

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Ecology & Evolutionary Biology
Arthur Weis

Final Exam Study Questions. 1. It is said there is a two-fold disadvantage of sex. Explain.  advantageous genotypes don't true breed ie. not all offspring have the advantageous genotype  reduced reproductive output (50% of offspring cannot bear children) 2. Asexual reproduction, over the longer term, is disadvantageous. What phylogenetic evidence supports that hypothesis.  - we only see asexual organisms very rarely  - asexual species only exist of very recent origin  - no example of a species that reverts back to sexual (maybe they die out too fast) 3. What is the Red Queen’s hypothesis, and how has it bee addressed experimentally??  - "you need to keep running to stay in the same place"  - need to constantly be generating new genetic combinations to deal with a constantly changing environment  - this has been tested experimentally with caenorhabditis  - faster tracking of shifting phenotypic optimum  Population of worms 4. Sex ratio’s are most often 50:50. How did R.A. Fisher explain this? When might a male- biased sex ratio evolve by selection?  rarity is always favored, this is called frequency dependant sex determination. the sex that is of a lower frequency will be favored by sselection because it will have a higher reproductive output. if there are a lot of males and a few females, an average female will have a better chance of mating, on the other hand if a male is rare, he will on average have more kids. these to opposing selections will push the frequency of the less common sex higher, closer to 50%. the 2 opposing selections will be in equilibrium and maintain the ratio. some cases a male will be favored when only few individuals can be produced in and environment with multiple females, like in parasatoid wasps. also in ant populations when there are multiple queens. Whenever there is a population with a female biased sex ratio, selection will favor the development of a male biased sex ratio. 5. Distinguish between sexual selection through male-male contests, and through female choice. 6. Explain the ideas of a) sensory bias and selection for male traits, b) runaway sexual selection of male traits and female choice, and c) the ‘good genes’ model for evolution of male traits and female choice. 7. Aggressive competition can be favored by selection, even if the spread of an aggression gene lowers population mean fitness. Explain. 8. What are the key features of cooperatively breeding species? What additional features are found in eusociality?  Were more then 2 individuals display parental-like behavior towards a offspring  Helpers provide a resource or a service to offspring that are not their own, often a siblings or an older offspring  Helpers can face a fitness cost for helping  Helpers can go on to reproduce later  Additional features that are found in eusociality are a joint defensible nest and the fact that helpers do not reproduce 9. What genetic features of the hymenoptera have bee thought to predispose them to the evolution of eusociality? 10. Define each of the following The Typological Species Concept The Phylogenetic Species Concept The Biological Species Concept (What makes it biological?) typological species concept: a group of similiar individuals that conform to an ideal individual type phylogenetic Species concept: a cluster of indivuduals that are distinct from other clusters, all descendants from a common ancsetor Biological species concept: a group of interbreeding or potentially interbreeding populations that are isolated from other such groups reproductively. This can be due to many different reasons. 11. What are the four geographical modes of speciation? allopartic speciation: a new physical barrier arieses that leads to no gene flow peripartic speciation: a new population of individuals is created that doesnt have gene flow with the original parapartic speciation: a range expands with strong divergent selection and limited gene flow sympatric speciation: sexual isolation in the same geographic area in an initially random mating population 12. Define and give an example for each Ecological Isolation: different time or place of mating like spring vs fall cricket Sexual Isolation: different mating preferences lacewing songs Mechanical or Gametic incompatibilitie: when the structure of the sex organs don’t allow meeting of the gametes or when the gametes cannot fuse. Different drosophila species with different penis styles Hybrid Sterility: when the hybrid is sterile like a mule Hybrid Inviability: when there are developmental issues and the offsping cannot survive like sunfish species intermating ecological isolation: where gene flow is restricted due to different times of mating or different areas of mating. ex is the spring field cricket and the fall field cricket 4 sexual isolation: is when gene flow is restricted because of differences in mating preferenc
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