Exam (elaborations)
BIO 182 Exam 2 Questions and answers latest update 2024
- Course
- BIO 182
- Institution
- Arizona State University
BIO 182 Exam 2 Questions and answers latest update 2024
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BIO 182 Exam 2 How many modes of selection are there? - correct answer 3 What are the modes of selection? - correct answer Stabilizing selection, directional selection, and disruptive selection Stabilizing Selection - correct answer The mean of the trait remains similar over time but the standard deviation decreases Directional Selection - correct answer The mean phenotype shifts in a particular direction Disruptive Selection - correct answer The standard deviation of the trait increases as individuals with the mean value disappear. Stabilizing Selection Explained - correct answer The stronger the selective pressure against extreme phenotypes, the narrower the distribution of phenotypes will be in future generations. In the end, the size of the standard deviation will reflect both the strength of selection against extremes and the frequency of mutations creating new variation. Thus, when we observe a wide range of phenotypes in a population, we might infer weak selective pressure against the extremes. Directional Selection Explained - correct answer The population's environment changes. The mean phenotype in the population may no longer be the phenotype that reproduces the most. Over time, we should expect the mean phenotype to shift higher or lower, de pending on the direction of selective pressure. Once the mean phenotype catches up to the change in the environment, stabilizing selection will resume. The environment must change slowly enough for the population to persist. If the environment changes too quickly, no members of the population will be able to reproduce, leading to extinction. Disruptive Selection Explained - correct answer A population can occupy an environment in which individuals with extreme phenotypes reproduce more than individuals with the mean phenotype. This mode of selection occurs when several distinct strategies confer greater reproductive success than other strategies do. Can produce new species when individuals choose to mate only with similar -looking individuals. This non -random mating prevents reco mbination from restoring intermediate phenotypes. Evolution by Natural Selection - correct answer Heritable variation leads to differential reproductive success Selection and Fitness - correct answer Directional Selection Equation - correct answer y=bx+c y=relative fitness x= trait value b= strength of selection c=parameter True or False? If the slope of the relationship between the phenotype and fitness is positive, natural selection would decrease the phenotype over generations. - correct answer False, it would increase the value of the trait over time Stabilizing Selection Equation - correct answer y=ax^2+bx+c y=relative fitness x= trait value a/b= strength of selection c= parameter True or False? If the parameter for the squared term is negative, natural selection will likely stabilize the phenotype at an intermediate value. - correct answer True, depends on how large the parameter is for the squared term What is fitness? - correct answer The relative number of viable, fertile offspring What does natural selection do? - correct answer Natural selection not only changes mean phenotypes but also increases or decreases deviations from mean phenotypes. What type of selection is most common? - correct answer All three can happen to some extent. Both the direction and the strength of natural selection varies greatly among traits and species. True or False? Directional selection is more likely to be weak than strong. - correct answer True True or False? Stabilizing selection occurs more often than disruptive selection. - correct answer False The next 5 questions are based on the following story: - correct answer A researcher studied the relationship between the phenotypes of snakes and their fitness. First, he measured the color patterns and the escape behavior of hundreds of snakes. For color pattern, snakes were scored as being either checkered or striped (see photos below). For escape behavior, snakes were chased by simulating a predator attack; some snakes moved in a straight line while fleeing, but others tended to turn frequently. After r ecording these phenotypes, the researcher released the snakes in their natural environment. A year later, he returned to see which snakes had survived. The survival of snakes was used as a proxy of fitness. The figure below shows the relationships between color pattern and relative fitness for snakes that flee straight and snakes that flee by turning. 1. A snake with stripes would be more likely to survive by fleeing predators in a straight line. (T/F) - correct answer True 2. Regardless of escape behavior, the color pattern of snakes will be influenced by directional selection. (T/F) - correct answer True 3. Over many generations, the population of snakes should evolve toward striped snakes that flee by turning or checkered snakes that flee straight. (T/F) - correct answer False 4. The strength of selection for a color pattern is greater in snakes that flee by turning than in snakes that flee straight. (T/F) - correct answer True 5. Although the researcher estimated fitness by survival, he could have also used another proxy for fitness, such as mating success. (T/F) - correct answer TrueThe benefits of buying summaries with Stuvia:
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