Evolution: Mutation and Selection Gizmo Answer Key

Name: Quintin Lowery Date: 10-01-2022 Student Exploration: Evolution: Mutation and Selection Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: adaptation, allele, allele sequence, chromosome, evolution, fitness, gene, genotype, mutation, natural selection, phenotype, trait Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Imagine a white lizard and a brown lizard sitting on a brown rock. A hawk is circling overhead hunting for its next meal. Which lizard do you think the hawk would most likely try to catch? Explain your choice. The white lizard, as it stands out more and is easier to see. 2. Now imagine that the same two lizards were sitting on a dune of white sand. Which lizard do you think the hawk would then most likely try to catch? Why? The brown lizard, as it stands out in contrast to the surrounding white sand. Gizmo Warm-up How long could a parrot survive in Antarctica? It would probably not survive long. Parrots do not have adaptations—or helpful characteristics—to survive icy cold weather. Because of this, a parrot is not fit for Antarctica. Fitness describes how well an organism can survive and reproduce in an environment. In the Evolution: Mutation and Selection Gizmo, you will see how a species’ fitness can change over time as it becomes better adapted to its environment. 1. On the SIMULATION pane, what is the Average fitness of the population? 50 2. On the CONTROLS pane, experiment with the Background color sliders. A. Which background color results in the highest fitness? Green B. Which background color results in the lowest fitness? Blue Activity A: Inherited variation Get the Gizmo ready: ● Set Red to 100, Green to 255, and Blue to 50. Introduction: An organism’s traits, or characteristics, are controlled by genes. Genes are located on rod-like structures called chromosomes. Different versions of genes that code for the same trait are called alleles. In this Gizmo, there are 3 genes on each chromosome. For each gene there are eight possible alleles: W (white), R (red), G (green), B (blue), C (cyan), M (magenta), Y (yellow), and K (black). Question: Where does variation in a population come from? 1. Observe: Hold your cursor over one of the insects. The two rod-like structures under Genotype on the right side of the Gizmo represent chromosomes. The three letters next to each chromosome represent alleles. Which alleles does the insect have? 6 The alleles carried on an organism’s chromosomes make up the organism’s genotype. 2. Observe: An organism’s alleles combine to produce a trait. The physical expression of that trait is a phenotype. In the Gizmo, phenotype is expressed in red, green, and blue values. A. What is the phenotype of the insect? B. What color is the insect? Red: 255 Green: 255 Blue: 255 White 3. Run Gizmo: Move the Sim. speed slider all the way to the left. Click Play ( ). You will see the insects move to the left in pairs. The pairs mate and produce a set of four offspring. As soon as you see at least one offspring with an oval around it, click Pause ( ). Move your cursor over the circled offspring. A. What is its genotype and phenotype? Genotype- YW, WW, WW Phenotype- red: 255, green: 255, blue:213 B. How does its genotype and phenotype differ from the non-circled offspring? All of the offspring without circles are white. 4. Explain: The change in the circled offspring’s genotype was caused by a mutation. A mutation is a change in a gene. Mutations happen when a mistake is made when a cell’s chromosomes are copied. How might mutations introduce variation into a population? When a mutation takes place, it then generates children, who carry the new gene and add variation to the population. 5. Collect data: Move the Mutation rate slider to 3.0, and click Play. Allow the Gizmo to run for another 10–15 generations. (You can see the generation number below the insects.) Click Pause when the parents are ready to have offspring. Find a set of two parents that has four different chromosomes. (If you can’t find any, allow the Gizmo to run a few more generations and try again.) Write the allele sequences for these parents in the table below. Note the labels for each of these chromosomes: A1, A2, B1, and B2. Organism: Parent A Parent B Allele sequence of chromosome 1: Y, B, W, W (A1) Y, W, W (B1) Allele sequence of chromosome 2: W, G, W, WY (A2) Y, Y, W (B2) Click Play, and then click Pause immediately after the offspring are produced. Write the allele sequences of chromosomes 1 and 2 for each of the offspring of your selected parents. Offspring Allele sequence of chromosome 1 Allele sequence of chromosome 2 Offspring 1 W,W,W (A1) W,C,R(A2) Offspring 2 W,W,W(B1) W,Y,W(B2) Offspring 3 Y,W,W(A1) W,Y,W(A2) Offspring 4 W,W,B(B1) W,Y,W(B2) Label the offspring chromosomes A1, A2, B1, or B2. Circle any mutated chromosomes. 6. Analyze: Study the completed table. A. Look at the inheritance patterns. What do you notice? Offsprings have a combination from each parent B. Can a single offspring inherit both chromosomes from one parent? Explain: It is not common just because you are receiving the dna from two parents C. Did any mutations occur in this set of offspring? If so, which chromosome mutated? No 7. Challenge yourself: You have already learned that mutation is one source of variation in a population. Based on what you have just seen, what is a second source of variation? Gene flow, or the transfer of genes between various groups of organisms, occurs constantly. Activity B: Survival of the fittest Get the Gizmo ready: ● Click Reset ( ). ● Set Red to 255, Green to 0, and Blue to 130. ● Set the Mutation rate to 1.0. Question: Are some organisms more likely to survive and reproduce than others? 1. Count: Move the Sim. speed slider all the way to the left. Click Play. A. After the parents mate, click Pause. How many offspring are there? 20 B. Click Play. After the birds eat, click Pause. How many offspring are left? 10 In nature, as in the Gizmo, more offspring are born than can survive long enough to reproduce. Because of this, the offspring must compete with one another for survival. In this Gizmo, the insect offspring compete to avoid being eaten by birds. 2. Observe: Move the Sim. speed slider one notch to the right. Click Play, and wait for about 20 generations to pass. You should see a variety of insect phenotypes. (If not, click Play and wait until you do.) A. What different colors of insects do you see? Red, orange, and purple B. How do you think this variation might affect the competition between the offspring? Because different varieties of insects require different things, specific insects will thrive in certain environments. 3. Analyze: Scroll over the insects and note their fitness (shown under the Phenotype). The fitness of an organism reflects how likely it is to survive and produce offspring. Each insect is given a percentage that reflects its chances of surviving to reproduce. Compare the fitness percentages to the insect colors. How does fitness relate to the color of the insects? Insects with chromosomes that are comparable to those of their parents are more likely to be fit. 4. Predict: How do you think an insect’s fitness will affect is chances of being eaten by birds? The likelihood of it being eaten by birds decreases if it is higher. 5. Collect data: In nature, chance alone can affect whether an individual survives. However, general trends in survival rates can be seen by studying a larger group of individuals. Move the Sim. speed slider all the way to the left. Click Play, and then click Pause when all the offspring are visible. Write the generation number and the average fitness of all the offspring in the first two spaces of the table below. Next, click Play, and then click Pause immediately after the birds have fed and the 10 survivors are visible. Mouse over each survivor and record its fitness. Find the average fitness of the survivors by adding these values and dividing by 10. Repeat this experiment two more times, recording your results in the table. Generation Ave. fitness Survivor fitness values Ave. survivor fitness 15 52.1 50,56 51.2 41 73.4 72,73,73,83 74.1 125 83.85 73,94,83 88.6 6. Recognize trends: Study the table above. What trends do you see? The level of survivor fitness increases with generational age. 7. Analyze: In most situations, were the fittest insects or the least fit insects most likely to survive? Explain how the data from your experiment supports your answer. The likelihood of survival rose with each generation, favoring the fittest individuals. 8. Think and discuss: The principle of natural selection states that the best adapted organisms are most likely to survive and reproduce. Was this demonstrated in your experiment? Explain. Yes, it was shown because the average increased as a result of the surviving procreating. Get the Gizmo ready: Activity C: ● Click Reset. Set Red to 100, Green to 255, and Blue to 50. Evolution Introduction: You learned in activity B that fit individuals have a better chance of surviving and reproducing than individuals that are less fit. In this activity, you will observe how natural selection affects a population over time. Question: How does a population change over time? 1. Experiment: Set the Background color to the values shown in the last column of the table below. Record the Average fitness of generation 1 in the second column of the table. Move your cursor over the insects and find the individual with the greatest fitness. (In the first generation, all the insects will have the same fitness). Record that individual’s phenotype in the table’s third column. Move the Sim. speed slider a quarter of the way to the right. Run the Gizmo, and complete the table for each listed generation. (The generation number does not have to be exact.) Generation number Average Fitness Fitness of Fittest Individual Phenotype of Fittest Individual (R, G, B) 1 53 53 W,W,W 25 65 75 K,W,G 50 64 75 K,G,W 75 92 95 W,Y,G 100 92 97 G,G,Y 150 93 97 G,G,Y 200 93 97 G,G,Y 300 93 97 G,G,Y Background color red = 100 green = 255 blue = 50 2. Describe: Examine the data collected for trends. A. How did the phenotype of the fittest individual change over time? Nothing materially changed. B. How did the population’s fitness change over time? Because the majority of the population had the same survivor fitness, there was minimal change. The process by which populations change over time is known as evolution. This Gizmo only demonstrates how one trait—body color—can evolve. 3. Predict: Based on what you have just seen, how do you think the population will evolve if you made the Background color purple? The general level of survivor fitness will rise. 4. Test: Set Red to 120, Green to 0, and Blue to 160 to make a purple background. Click Play. After 300 more generations have passed, click Pause. Was your prediction correct? Explain. Because the average rose with time, it was accurate. 5. Make connections: Why do you think it is necessary for there to be variation in a population in order for evolution by natural selection to occur? There are therefore many distinct types of bugs. 6. Make connections: Why is it necessary for traits to be inherited for evolution to take place? Therefore, the qualities that the various insect species inherit from their parents alter over time. 7. Apply: Look carefully at the picture below and you will see an insect called a katydid. Katydids evolved from grasshoppers through natural selection. Use what you have learned to explain how this could have happened. This might have occurred because of the environment in which they inhabit, where they have to develop camouflage in order to survive, and where it has continuously improved over time. Additionally, it was consistently inherited from generation to generation.