Name: Date: 2021-01-13 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 (Do these BEFORE using the Gizmo.) 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 moth and a light, speckled moth. Birds are a frequent predator of the peppered moth. 1. Which morph do you think would be easier to see on a dark tree 2. Which morph do you think would be easier to see on a light tree 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 ( ), and hunt moths for one year. A. How many dark moths did you capture? 6 B. How many light moths did you capture? 6 C. Camouflage is coloring or patterns that help an organism to blend in with the background. Which 2. If a forest contained mostly light-colored trees, which type of moth would you expect to be most common? Gizmo Warm-up light moth dark moth trunk? Light speckled moth trunk? type of moth is better camouflaged on light bark? Light moth would be more common. Activity A: Light trees Get the Gizmo ready: ● Click Reset ( ). ● Check that the LIGHT TREES tab is selected. 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 happen to the populations of light and dark moths on light trees? 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 44% 56% 2 41% 59% 3 48% 52% 4 43% 57% 5 38% 63% 3. Analyze: What do your results show? 4. Apply: Which type of moth do you think was more common before the 19th century, when most trees were light in color? Over time, the dark moth population would decrease quicker than light moths population The results show that the dark moth population decreased over the years while the light moth population increased. Light moth was more common before the 19th century. 5. Extend your thinking: What strategies did you use to hunt for moths? Activity B: Dark trees Get the Gizmo ready: ● Click Reset. ● Select the DARK TREES tab. 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 happen to the populations of light and dark moths on dark trees? 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 54% 46% 2 56% 44% 3 58% 42% 4 52% 48% 5 59% 41% 3. Analyze: What do your results show? 4. Apply: Which type of moth do you think was more common during the 19th century? Why? I hunted for the dark moths first because they were easily visible, and after I was done capturing the dark moths, I looked for the light moth since they were harder to find. Light moths population would decrease and dark moths population would increase. The results show that the dark moths population increased over the years while light moth population decreased. 5. 6. 7. 8. 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? 9. 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. 10. 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. Dark moths were more common during the 19th century because the moths had adapted to the environmental changes due to the Industrial Revolution which helped them camouflage on the dark tree trunks, making them harder to be seen by predators. In both the light tree experiment and dark tree experiment, the moths had favourable traits that helped increase the frequency of that particular moth. Light moths on light coloured trees had favourable traits which helped them increase in frequency because they were harder to find and dark moths on dark coloured trees had favourable traits which helped them increase in frequency, because they were harder to find. The changes in the moth population occurred because the best-hidden moths survived and reproduced, passing on their colours to their offspring. This is because the best-hidden moths had favourable traits which helped them camouflage to the tree, and these favourable traits were passed on to their offsprings, which increased its frequency. Natural selection is the process that results in a better adapted population through inherited favourable traits. Organisms with advantageous traits are able to survive the current environment and pass the traits down their offsprings. Over the years the passed on traits change the population to better suit the environment, which results in evolution since evolution is the change in a population that occurs over time