Biol 471 Exam 2 (A+ GUARANTEED)

What is reinforcement? How does it play out? What is it's role in the speciation process? correct answers secondary contact is for selection to "reinforce" existing isolating mechanisms -selection favors the evolution of prezygotic isolating mechanisms -hybrids unfit-> selection favors assortative mating-> mate preferences lead to decline in hybridization -Coyne and Orr: prezygotic isolation evolves faster in sympatric species -mate choice based on toad calls How is reproductive isolation expected to evolve between geographically isolated populations vs. populations that are not isolated? correct answers isolating mechanisms: biological properties of individuals which prevent the interbreeding of populations that are actually sympatric -Geographic Isolation: different selective environments, founder effect-> diverging through chance events -Same Geography: behavioral, morphological, physiological, genetic, biochemical features Is physical separation an isolating mechanism? correct answers although a physical barrier can be instrumental in the evolution of isolating mechanisms, physical separation, by itself, does not constitute an isolating mechanism: unless individuals have evolved features that prevent interbreeding, they would interbreed as soon as they came into sympatry with each other. What is the biological species concept? What are its limitations? Strengths? correct answers Ernst Mayr groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups -Two populations are reproductively isolated from each other even if in same habitat (physical barrier not necessary) -not same species if they hybridize under artificial conditions -Limitations: fossils, prokaryotes, reproductive isolation is not absolute -> ring species ( -Strengths: easily testable What are species? correct answers fundamental units of biodiversity -a separately evolving meta-population lineage Why is gene flow so important in defining species? correct answers -In the absence of gene flow, different patterns of selection, random genetic drift, and mutation will send organisms on separate evolutionary trajectories -in the presence of gene flow, each group tends to lose its evolutionary independence and also its distinctive characteristics. Dispersal correct answers colonizing a new area, uninhabited area colonized by source pop and evolve in new area