Z101--Mechanisms of Evolution & Modes of Selection Packet

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University of Wisconsin, Madison *

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101

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Biology

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Dec 6, 2023

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pdf

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PRACTICE QUESTIONS: Mechanisms of Evolution & Modes of Selection Spring 2023 ©Juanita Diaz 2023 Determine whether each of the following scenarios is a result of mutation, genetic drift, or gene flow. If the scenario is a result of genetic drift, identify whether it is a result of the founder’s effect or the bottleneck effect. A large deletion in chromosome 16 of soybean plants results in seeds with a higher sucrose content than seeds from soybean plants without the deletion. There are some Trachelipus rathkei (a terrestrial isopod) populations that live in normal habitats and some that live in habitats that are polluted by heavy metals. The populations that live on the polluted habitats have adaptations that allow them to safely process levels of heavy metals that would be toxic to T. rathkei from normal habitats. Some T. rathkei from normal habitats disperse to polluted habitats, mate with individuals from the polluted habits, and have offspring that are not as good at processing heavy metals. After a hurricane, a small group of green iguanas floated across the ocean on a raft of logs and uprooted trees to an island that did not have any iguanas. This small group established a new population on the island. Over the past 10,000 years, European wolf populations have experienced severe population decline due to habitat fragmentation and overhunting, such that the current European wolf populations are much smaller than their prehistoric populations. Although current wolf populations are starting to grow, they have very low genetic variation. Eurytemora affinis (a species of copepod) individuals can be transported in ship ballast water between populations in the North and Baltic Seas. Individuals from a freshwater population are transported to a high salinity population, breed with individuals from the high salinity population, and introduce alleles for freshwater tolerance into the population. Certain variants of the Fibrillin 1 gene ( FBN1 ) are associated with differences in height in Peruvian individuals. The difference in height is caused by a change in one base-pair of the FBN1 gene that results in a different amino acid being added to the protein, and is associated with shorter height in the individuals who have it. Picture credit: Carol Lee Picture credit: Katja Schulz

PRACTICE QUESTIONS: Mechanisms of Evolution & Modes of Selection Spring 2023 ©Juanita Diaz 2023 Each of the following scenarios are an example of natural selection. Determine whether each of the scenarios is a result of diversifying (disruptive) selection, directional selection, or stabilizing selection. Albino deer (deer with white fur) are easy for predators to see and experience high mortality compared to deer with brown fur. The asp viper can be one of several color morphs. The melanistic morph (dark, solid color) snakes are found in mountainous regions, where the dark color provides increased thermoregulation. The blotched morph (blotches of light and dark color) snakes are found in wooded areas at lower elevations, where their coloration provides camouflage in their forest environment. Morphs that are intermediate between the melanistic and blotched morphs are not common. Large hawkmoths ( Agrius convolvuli ) eat nectar found at the end of flower-tubes of the South Africa iris, which are very long. Large hawkmoths have very long tongues to reach the nectar. Large hawkmoths with tongues that are too short are unable to reach the nectar, which means they are unable to eat. Antelopes are unable to outrun/outmaneuver predators if their legs are too short, but are prone to breaking bones if their legs are too long. One gene that underlies lateral plate (i.e., armor) formation in threespine stickleback is Ectodysplasin ( Eda ). The ancestral allele for Eda is found in marine stickleback and results in robust armor. A (relatively) new allele for Eda is found in freshwater stickleback and results in reduced armor. The amount of armor has been related to predation pressure → heavy armor is advantageous in marine habits with fish and bird predators, while reduced armor is advantageous in freshwater habits with insect predators. In Italy, germination of Arabidopsis thaliana (a plant) mainly occurs during November. Seeds that germinate earlier or later have low fitness and usually don’t survive. Picture credit: Dave Hone Picture via: https://portal.ct.gov/DEEP/Fishing/Freshwater/Freshw ater-Fishes-of-Connecticut/Threespine-Stickleback

PRACTICE QUESTIONS: Mechanisms of Evolution & Modes of Selection Spring 2023 ©Juanita Diaz 2023 Each of the following scnarios is an example of sexual selection. Determine whether each of the scenarios is a result of intrasexual selection or intersexual selection. Female seahorses with larger body sizes are more attractive to males (and more likely to be chosen as mates) than females with smaller body sizes. Male birds of paradise have elaborate courtship dances and plumage to attract females. Female wattled jacana birds use their large size and spurs to fight other females for access to breeding territory and to protect their eggs. Male elk use their antlers to fight other males for access to territory and mates. Picture credit: Tim Laman Picture via: https://www.youtube.com/watch?v=oxwDsGRnBjs

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