Exam (elaborations) GIZMOS Student Exploration Evolution Mutation And Selection

Exam (elaborations) GIZMOS Student Exploration Evolution Mutation And Selection Vocabulary: adaptation, allele, 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 hawk would most likely try to catch the white lizard as it is easier for the hawk to spot it. 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 hawk would most likely try to catch the brown lizard as it is easier for the hawk to spot it. 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? white B. Which background color results in the lowest fitness? black This study source was downloaded by from CourseH on :34:18 GMT -05:00 This study resource was shared via CourseH GIZMOS Student Exploration Evolution Mutation and Selection Activity A: Variation Get the Gizmo ready:  Set the red value to 100, the green value to 255, and the blue value to 50 on the CONTROLS panel. Introduction: An organism’s traits, or characteristics, are controlled by genes. Genes are located on rodlike structures called chromosomes. Different versions of genes that code for the same trait are called alleles. In this Gizmo, eight alleles control the color of bugs. Question: Where does variation in a population come from? 1. Observe: Hold your cursor over one of the insects on the SIMULATION pane. The two rod-like structures under Genotype on the CONTROLS pane represent chromosomes. The three letters next to each chromosome represent alleles. Which alleles does the insect have? WWW and WWW The alleles carried on an organism’s chromosomes make up the organism’s genotype. 2. Observe: An organism’s alleles interact to produce a certain trait. The physical expression of that trait is known as an organism’s phenotype. In the Gizmo, phenotype is expressed in RGB (red, green, blue) values. What is the phenotype of the insect? Red:255 Green:255 Blue:255 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: WWW and YWW Phenotype: 255 red, 255 green, 213 blue B. How does its genotype and phenotype differ from the non-circled offspring? It has different genes, which means it's colored differently. 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 during the copying of a cell’s chromosomes just before the cell divides. How might mutations cause variation into a population? Different colors or attributes that helps them survive longer. This study source was downloaded by from CourseH on :34:18 GMT -05:00 This study resource was shared via CourseH 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 on the bottom left of the SIMULATION pane.) Click Pause. Try to find a set of parents that has four different chromosomes. (If you can’t find any, allow the Gizmo to run a few more generations and try again.) Complete the table. Organism Genotype of chromosome 1 Genotype of chromosome 2 Parent A KCK WBW Parent B WGW WMK Offspring 1 KCK WMK Offspring 2 KCK WGW Offspring 3 KCK WMK Offspring 4 KCK WGW Look at the offspring chromosomes. Label the chromosomes identical to parent A’s chromosome 1 with “A1.” Likewise, label copies of parent A’s chromosome 2 with “A2,” parent B’s chromosome 1 with “B1,” and parent B’s chromosome 2 with “B2.” Circle any mutated chromosomes. 6. Analyze: Study the completed table. A. Look at the inheritance patterns. What do you notice? Offspring had a combination of chromosomes from each parent. B. Can a single offspring inherit chromosomes from only one parent? Explain. Yes. C. Did any mutations occur in this set of offspring? If so, which chromosome mutated? No chromosomes mutated. 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? Activity B: Survival of the fittest Get the Gizmo ready:  Click Reset ( ).  Set red to 100, green to 255, and blue to 50.  Move the mutation rate slider to 1.0. This study source was downloaded by from CourseH on :34:18 GMT -05:00 This study resource was shared via CourseH Question: Are some organisms more likely to survive and reproduce than others? Yes. 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 offspring. B. Click Play. After the birds eat, click Pause. How many offspring are left? 10 offspring. In nature, as in the Gizmo, more offspring are born than can survive. 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 20 generations to pass. You should see a variety of insect phenotypes. A. What different colors of insects do you see? Purple, pink and light gray. B. How do you think this variation might affect the competition between the offspring? The more colorful ones will be more easily eaten. 3. Analyze: Scroll over the insects and note their fitness (shown under the Phenotype). The fitness of an organism reflects how well it is adapted to its environment. How does fitness relate to the color of the insects? The more the insect's color matches its background, the higher its fitness level. 4. Predict: How do you think an insect’s fitness will affect is chances of being eaten by birds? The higher its fitness, the less likely it will be eaten by a bird. 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. Use the Gizmo to study survival trends for five generations. Record the data you collect in the table below. Write the Generation num and Average fitness in the first two columns. To find the average fitness of the survivors, click Pause after the birds feed. Add the ten surviving offspring’s individual fitness values together and divide by ten. Generation number Average fitness of generation Average fitness of survivors 20 66% 66% 21 66% 66% This study source was downloaded by from CourseH on :34:18 GMT -05:00 This study resource was shared via CourseH 22 66% 66% 23 66% 66% 24 66% 66% 6. Recognize trends: Study the table above. What trends do you see? N/A 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. Fittest insects are more likely to survive. 8. Think and discuss: The principle of natural selection states that the fittest organisms are most likely to survive and reproduce. Was this demonstrated in your experiment? Explain. Activity C: Evolution Get the Gizmo ready:  Click Reset. 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 th