Types of Selection (Worksheet Answers)

Name: ANSWERS Types of Selection Worksheet 1 Case: Identify the different types of natural selection and describe how a population will evolve over time. Read the following situations below and identify the 5 Points of Darwin's theory. There are 2 types of worms: worms that eat at night (nocturnal) and worms that eat during the day (diurnal). The birds eat during the day and are able to be eating ONLY the diurnal worms. The nocturnal worms are therefore increasing in number. Each spring when the worms reproduce, they have about 500 babies but only 300 of these 500 ever become old enough to reproduce. a. What worm has natural selection selected AGAINST: Diurnal b. Nocturnal Darwin's 5 points: Identify the 5 points in the scenario above. Population has variations: Diurnal vs Nocturnal Nocturnal Some variations are favorable. More offspring are produced than survive. 500 born, 100 survive Those that survive have favorable traits. Nocturnal, avoid birds A population will change over time. Shift towards nocturnal There are 3 types of polar bears: ones with thick coats, ones with thin coats and ones with medium coats. It is fall, soon to be winter. The temperatures are dropping rapidly and the bears must be kept warm, or they will freeze to death. Many of the bears have had <2 cubs each but due to the extreme temperatures, many mothers only have one cub left. c. What bear will natural selection select AGAINST? Thin/Medium d. Thick. Darwin's 5 points: Identify the 5 points in the scenario above. Population has variations. Thin/medium/Thick Some variations are favorable. Thick is favored More offspring are produced than survive. 2 born, 1 survive Those that survive have favorable traits. Thick, fat, warmer A population will change over time. Shift toward Thick Bob believes that giraffes have long necks because they have stretched their necks to try and reach food that is high in trees. Since the parent had stretched its neck, it passed the long neck on to its offspring. Ryan believes that giraffes have long necks because the ones with long necks were able to reach the food, and those with short necks could not and died. The long necked giraffes reproduced, and soon all of the giraffes had long necks. a. Who thinks like Lamarck? Why? Bob, acquired b. Who thinks like Darwin? Why? Ryan, random traits & selection. BUNNY Selection vs a Single-Gene Trait A color mutation occurred in brown mice, causing darker fur. The table shows population changes over 30 generations. [Image shows a table with mouse populations across generations, but the text is not clearly legible enough to transcribe accurately, only the general shape of mouse silhouettes is visible.] What is happening to the relative frequency of the lighter fur color allele? Decreasing What is happening to the relative frequency of the darker fur color allele? Increasing Is the darker color mutation favorable or unfavorable? Favorable What may have caused the change in the population shown in the table? Predation? Predict how the mouse population will look after 40 generations. How were you able to make this prediction? Appears to be maining towards all dark. Label the three types of natural selection illustrated below: [Image shows three graphs with bell curves. Graph 1: Two peaks, labeled "Directional, Directional" Graph 2: One peak shifted to the right, labeled "Directional, towards large-" Graph 3: A narrower peak, labeled "Stabilizing"] What type of individuals in the population are represented by the 2 ends of the bellcurve? The extremes for a trait. Starling produce an average of five eggs in each clutch. If there are more than five, the parents cannot adequately feed the young. If there are fewer than five, predators may destroy the entire clutch. This is an example of: a. disruptive selection. c. directional selection. b. stabilizing selection. d. none of the above. no average The occurrence of large or small beak sizes among seed crackers in the absence of medium sized beaks is an example of: a. directional selection. c. disruptive selection. b. stabilizing selection. d. none of the above. A scientist measures the circumference of some oak tree population of oak trees and discover that the most common circumference is 2 cm. What would you expect the most common circumference(s) to be after 10 generations of stabilizing selection? a. 2 cm c. greater than 2 cm and less than 2 cm b. greater than 2 cm or less than 2 cm d. Can't tell from the information given Refer to question / but this time answer what you would expect after 10 generations of disruptive selection. Both a. 2 cm c. greater than 2 cm and less than 2 cm b. greater than 2 cm or less than 2 cm d. Can't tell from the information given 16. Each of the following is an example of stabilizing, disruptive, or directional selection—choose the correct form for each example, explain why it fits in their category and sketch the appropriate graph. 16. Larger squirrels can carry larger acorns to their homes, and they outcompete smaller squirrels when acorn supplies are limited. Directional, towards larger. Spotted brown-and-white butterflies blend into lichen-covered tree bark, making it difficult for predators to see them, while solid brown and solid white butterflies are easier to see and get eaten. Ends of Directional, towards spotted, away from solid. Furthmore teeth that are too short have difficulty capturing prey, while panthers with teeth that are too long have difficulty chewing their food. Stabilizing, maintain average In a lake in South Africa, puppies are eaten by the pike fish, and the larger the puppy, the more difficulty it has escaping its pike fish predator. Directional, toward smaller, away from larger. The rocks at the bottom of a stream are either black or white. Snails that live on these rocks are a mange of color from solid black to grey to solid white. A local freshwater fish loves to munch on these snails, but it cannot see the solid black or solid white snails when the snails are on matching rocks. Grey does blend into either rock color and is much easier to see. Bidirectional, diverging (extremes) be away from gray. Human babies usually do not survive if they are born too large because the mother cannot give birth. But they do not survive if they are born too small because the mother would not be able to give birth without dying. Stabilizing, maintain average.