Student Exploration Natural Selection

Name: Date: 2/2/2021 Student Exploration:Natural Selection Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: biological evolution, camouflage, Industrial Revolution, lichen, morph, natural selection, peppered moth Prior Knowledge Questions The peppered moth (Biston betularia) is a common moth found in Europe, Asia, and North America. It is commonly found in two forms, or morphs: a dark morph and a light, speckled morph. Birds are a frequent predator of the peppered moth. 1. Which morph do you think would be easier to see on a dark tree trunk? light 2. Which morph do you think would be easier to see on a light tree trunk? dark The Natural Selection Gizmo allows you to play the role of a bird feeding on peppered moths. The initial population of 40 moths is scattered over 20 tree trunks. Click on moths to capture them. Click the Next tree button (or the spacebar on your keyboard) to advance to the next tree. 1. Check that LIGHT TREES is selected. Click Play ( for one year. ), and hunt moths A. How many dark moths did you capture? 1 B. How many light moths did you capture? 0 C. Camouflage is coloring or patterns that help an organism to blend in with the background. Which type of moth is better camouflaged on light bark? 2. light If a forest contained mostly light-colored trees, which type of moth would you expect to be most common? light moths Activity A: ● Click Reset ( ). ● Check that the LIGHT TREES tab is selected. Light trees Introduction: Before the 19th century in England, the air was very clean. The bark on trees was usually light in color. Abundant lichens growing on tree trunks also lightened their appearance. Question: How does the color of a peppered moth affect survival? 1. Predict: Over time, what will to happen to the populations of light and dark moths on light trees? The dark moths are highly visible to predators against the light tree, but the light are nearly invisible to predators. So, it is likely that more dark moths will be captured by the predators, causing the population of light moths to decrease. The light moths population will increase because there are more of them to reproduce. 2. Experiment: Click Play and hunt peppered moths on light tree trunks for five years. In each year, try to capture as many moths as you can. Note: You can use the spacebar on your keyboard to quickly advance to the next tree. After 5 years, select the TABLE tab and record the percentages of each moth type. (Note: The table shows current populations of each moth, not the number of captured moths.) Year Dark moths Light moths 0 50% 50% 1 58% 42% 2 64% 36% 3 80% 20% 4 97% 3% 5 100% 0% 3. Analyze: What do your results show? The moths are living in an environment with dark trees so dark moths blend in better and are more likely to survive. 4. Apply: Which type of moth do you think was more common before the 19th century, when most trees were light in color? light moths were most likely more common because they blended in with light colored trees. 5. Extend your thinking: What strategies did you use to hunt for moths? I clicked the ones I could see, when white ones were completely invisible I clicked all over the screen to randomly get one but couldn't. Activity B: ● Click Reset. ● Select the DARK TREES tab. Dark trees Introduction: The 19th century was the time of the Industrial Revolution in England. Most of the new industries used coal for energy, and the air was polluted with black soot. In forests near factories, the soot coated trees and killed lichens. As a result, tree trunks became darker. Question: How did air pollution affect moth populations? 1. Predict: Over time, what will to happen to the populations of light and dark moths on dark trees? The light moths are highly visible to predators against the dark tree, but the dark moths are nearly invisible to predators. So, it is likely that more light moths will be captured by the predators, causing the population of light moths to decrease. The dark moth population will increase because there are more of them to reproduce. 2. Experiment: Click Play and hunt peppered moths on dark tree trunks for five years. In each year, try to capture as many moths as you can. When you are done, select the TABLE tab and record the percentages of each moth type. Year Dark moths Light moths 0 50% 50% 1 42% 58% 2 36% 64% 3 20% 80% 4 3% 97% 5 0% 100% 3. Analyze: What do your results show? The moths are living in an environment with light trees so light moths blend in better and are more likely to survive. 4. Apply: Which type of moth do you think was more common during the 19th century? Why? dark moths were most likely more common because they blended in with dark colored trees. 5. Draw conclusions: Natural selection is the process by which favorable traits tend to increase in frequency over time. How does this experiment illustrate natural selection? Since there were darker trees, dark moths had a better chance of surviving through having a favorable trait like mostly black color and that illustrates natural selection because the black moths got a favorable trait that tended to increase overtime. 6. Think and discuss: Did the changes you observed in the moth populations result from individual moths changing colors? Or did they occur because the best-hidden moths survived and reproduced, passing on their colors to their offspring? Explain your answer. A mix of the two, being a black moth of course helped immensely and pretty much meant having to put not a lot of effort into hiding, but if a white moth is really skilled and well hidden somehow well it's possible but the latter is likely the answer. 7. Extend your thinking: Biological evolution is the process by which populations of organisms change over time. How could natural selection lead to evolution? If possible, discuss your answer with your classmates and teacher. Natural selection promotes evolution by increasing the gene frequencies of genotypes with greater fitness to the environment. Thereby, organisms with the most suitable phenotypes to the environment are selected to pass the changes to the next generation through reproduction.