Evolution and Selection

Evolution and Selection What mechanisms lead to changes in the diversity of species on Earth? Why? People make choices by selecting options they like best. The natural world also "selects" (although not as a conscious decision) when environmental conditions allow organisms with a particular generic trait to live healthier lives than other organisms. In this activity, we will explore how selection affects populations over time Model 1 - Desktop Swab Results E. coli bacterial variants from culture Variant P Variant Q Variant R Varient S E. coli culture from swab of desktop E. coli colonies on growth medium without triclosan E. cof colonies on growth medium with triclosan 1. What is the source of the bacteria in the culture tube in Model 1? The bacteria came from surabbing a desktop. 2. How many genetic variants of E.coli were present in the culture from the initial swab? Four 3. What variants of Ecoli are found on the dish grown without triclosan? Variants PQ, R, and S ure present on the dish that does not include triclosan. 4. Refer to the dish in Model I with the medium that included triclosan. 4. What variants of Ecoli are found on the dish grown with triclosan? The only variant present is S. d. What likely happened to the other variants of E.coli on the dish with the medium containing triclosan? They were killed by the triclosan. Evolution and Selection 163 5. Based on its effect on Ecoli, why is triclosan used as a cleaning agent? Is kills or prevents the growth of some types of bacteria. 6. Suppose the desktop swabbed earlier was cleaned with a solution containing triclosan. Would living E.coli remain? Support your answer. Yes, wuriant S grew on the plates containing triclosan after the initial swab. 7. Suppose the desktop was swabbed again after cleaning it with triclosan over a 9-month school year. When the sample was cultured only variant S was seen. 4. What characteristic does the variant 5 bacteria have that allows it to remain on the desktop even after several months of treatment with triclosan? A trait that prevents the triclosan from affecting or killing the bacteria and allows them to gros even when triclosan is present. & Is it likely that the bacteria in the new swab were on the desk 9-months ago, or are they off-spring of the original bacteria? They are the offspring of the original bacteria. Propose an explanation for the presence of only variant S on the desktop after so much time. Only variant S would survive to reproduce in this environment. The triclosan-resistance trait would be paned on to the offspring. Other bacteria would be inhibited or killed by triclosan and would probably not reproduce, eventually dying out completely. Only bacteria that are resistant to triclosan and their offspring would remain Read This! Populations of most living organisms exhibit genetic diversity among individuals. Certain traits in a population give some organisms a greater chance of survival than individuals that lack these traits. Because these traits tend to increase the chance of survival, these individuals may produce more offspring that will also have the trait that favors survival. Over time, the number of individuals within the population pos-sessing the favorable trait increases while the number of offspring with the favorable trait decreases. Model 2 - Color Variations in Moths in Great Britain Peppered Moth Frequency 100 90 70 00 Percentage of Moths Captured 50 40 30 20 10 1800 1850 1900 1950 2000 Light modu Dark moths Years 8. Refer to the graph of Peppered Moth Frequency in Model 2. Which moth color was more prevalent before 1850? Light maths were more prevalent before 1850 6. Which color was more prevalent between 1900 and 19502 Dark moths were more prevalenz besucen 1900 and 1950. 9. Describe the change in the percentage of light-colored moths and dark-colored moths between 1850 and 1900. The number of light-colored moths decreased while the number of dark-colored moths increased. 10. Describe the change in the percentage of light-colored moths and dark-colored moths between 1950 and 2000. The number of dark-colored moths decreased rapidly while the number of light-colored moths increased rapidly. 11. During the Industrial Revolution through the mid-20th century, factories and power plants, which burned coal, produced large quantities of soot and smog. Near industrialized areas, black powder covered surfaces, including the moth habitat 4. Which color moth would have a better chance of surviving predation (better camoflage to hide from predators) on this dark surface? The dark moths would be less likely to be seen by predators. 4. How does this help explain the change in the colors of the moth population shown in Model 2? Because the light-colored moths were easier to see on the dark surfaces, they were easier prey and could not have as many offspring as the dark-colored maths that were harder to see and could sur-vive langer.