AANT 110 Introduction to Human Evolution Assignment #1: Natural Selection Background In Module 1, you learned about Charles Darwin's discovery and development of a mechanism for evolution called natural selection. Simply stated, natural selection means that within any population with variation there is a struggle for existence that ultimately leads to the survival of the fittest. The continual selection for certain traits and against others over thousands to billions of years led to what Darwin called descent with modification. Different environments create selection pressure for certain traits over long periods of time cause an ancient ancestor of all life to be modified over and over again until it had evolved from a single species into all the species that have lived on Earth since. While Darwin defined the mechanism of evolution fairly accurately, there were two major components he was missing. Darwin had little to no idea what caused the variation he saw in nature and he could not explain how the variations he saw were passed from parent to offspring. It was not until Mendel's work on pea plants.were discovered that the theory of heredity was used to explain inheritance. Mendel's work also explained production of variation using the principles of dominant and recessive genes, which you learned about in Module 2. By the mid-1930s, the idea of (1) the production and redistribution of variation, and (2) the process of natural selection acting on variation, were combined in a comprehensive theory of evolution. This unification is known as the Modern Synthesis. The discovery of DNA as the hereditary molecule in the 1950s further explained the origins of variation within a population. This meant that instead of approaching evolution by looking at how an organism's phenotype (physical features) changed over time, scientists could study the evolution of an organism's genotype (allele combinations). This leads to our modern definition of evolution: A change in allele frequency from one generation to the next. In today's simulation, you will be observing how modifying variation using mutations in DNA can lead to the evolution of a population of organisms. But first... Q1. Describe the process of natural selection in your own words. You can answer this either as a paragraph or in a list format. Include all the necessary components and how these relate to each other, leading to change over time. C Experiment 1 In this experiment you will be examining the effect of a recessive mutation that changes the color of the organism, introduces variation in the population, and alters how it avoids predators. Q2. Prediction: Read through the experiment. Then in the space below hypothesize how the recessive mutation for brown fur will affect the evolution of this bunny population over the next 10 generations. When writing hypotheses, scientists use a common format: If, then. Example: If a plant receives fertilizer, then it will grow bigger. In this case, I would also like you to give a reason for your hypothesis (because...). 2 Step 1: When you are ready to start your first experiment make sure the environment is set to "equator" then click the "add a friend" button in the lower left-hand corner of the environment. This will start the simulation. Watch the generation bar, let it run down once, and then hit pause. Record the data from the graph for generation two in data table 1. This should be when your first pair of bunnies has reproduced once. Step 2: Once you've recorded the data, click on "Brown fur" in the add mutation section of the simulator. Using the edit genes section of the simulator change brown fur to a recessive trait. Step 3. Start the simulation and let it run for two more generations. At this point pause the simulation and use the graph to fill in generation 4 data in data table 1. Note: the generation bar does not have to run down all the way for the second generation. Your population bars should have four steps indicating increasing generations four times. Step 4. Now add wolves as a selection factor and start the simulation. Let the simulation run for three more generations. Hit pause and collect data for generation 7 on data table 1. Bause the HO Step 5. Click play and let the simulation run for three more generations. Pause the simulation and record the data for generation 10 in data table 1. Data table 1 Generation Graphical Data Percentage calculations Number of number Brown Number of White % Brown % White Total Rabbits Rabbits 2 4 7 10 Analysis: Calculate the percentage of each color of rabbit using the following method: % Brown rabbit % White rabbit (Brown rabbits / Total rabbits) X 100 100% -% brown rabbits. Q3. Briefly explain how the brown fur mutation affected the allele frequency of the population. Be sure to use your data in this explanation. Q4. Does the data in the table above support the hypothesis for this experiment? Be sure to use your data in an explanation of why the data does or does not support your hypothesis. I Experiment 2 In this experiment you will be examining the effect of a dominant mutation that affects how the rabbits obtain food. Q5. Prediction: Read through the experiment. Then in the space below hypothesize how the dominant mutation for long teeth will affect the evolution of this bunny C Q5. Prediction: Read through the experiment. Then in the space below hypothesize how the dominant mutation for long teeth will affect the evolution of this bunny population over the next 10 generations. (Remember....if, then, because statements) Step 1. Click the reset all button in the lower right hand corner of the simulator. Step 2. When you are ready to start your second experiment click on the "add a friend" button in the lower left hand corner of the environment. This will start the simulation. Watch the generation bar, let it run twice, then hit pause. Record the data from the graph for generation two in data table 2. Step 3. Once you've recorded the data click on "long teeth" in the add mutation section of the simulator. This mutation should already be designated as a dominant trait but check the edit genes section of the simulator to be sure. Step 4. Start the simulation and let it run for two more generations. At this point, pause the simulation and use the graph to fill in generation 4 data in data table 2. Step 5. Now add food as a selection factor and start the simulation. Let the simulation run for three more generations. Hit pause and collect the data for generation 7 on data table 2. Step 6. Click play and let the simulation run for three more generations. Pause the simulation and record the data for generation 10 in data table 2. Data table 2 Generation number Number of Normal teeth Graphical Data Number of Long teeth Total 2 4 7 10 Analysis: Percentage calculations % Normal % Long Tooth Tooth Rabbits Rabbits I HON Analysis: Calculate the percentage of each tooth type using the following method: % Long tooth rabbit (Long tooth rabbits / Total rabbits) X 100 % Normal tooth rabbit - 100% -% Long tooth rabbits. Q6. Briefly explain how this change in DNA affected the allele frequency of the population. Be sure to use your data in this explanation. Q7. Does the data in the table above support the hypothesis for this experiment? Be sure to use your data in an explanation of why the data does or does not support your hypothesis. Experiment 3 In this experiment you will be examining the effect of a dominant mutation that changes the length of the rabbit's tail. Your job in this simulation is to determine whether or not having a longer tail gives the rabbits an advantage (is a favorable trait) when trying to escape predators. Q8. Prediction: Read through the experiment. Then in the space below hypothesize how the dominant mutation for a long tail will affect the evolution of this bunny population over the next 10 generations. (Remember... if, then, because statements) Step 1. Click the reset all button in the lower right hand corner of the simulator. 5 Step 2. When you are ready to start your third experiment click on the "add a friend" button in the lower left hand corner of the environment. This will start the simulation. Watch the generation bar, let it run twice, then hit pause. Record the data from the graph for generation two in data table 3. I Step 3. Once you've recorded the data click on "long tail" in the add mutation section of the simulator. This mutation should already be designated as the dominant trait but check the edit genes section of the simulator to be sure. Step 4. Start the simulation and let it run for two more generations. At this point pause the simulation and use the graph to fill in generation 4 data in data table 3. Step 5. Now add wolves as a selection factor and start the simulation. Let the Мон ans 11 ABC A A AaBbCcDdEe A Aa Normal Text Box Themes 7 Step 5. Now add wolves as a selection factor and start the simulation. Let the simulation run for three more generations. Hit pause and collect the data for generation 7 on data table 3. Step 6. Click play and let the simulation run for three more generations. Pause the simulation and record the data for generation 10 in data table 3. Data table 3 Generation number Number of Short Tail Graphical Data Number of Long Tail Total % Short Tail Rabbits Percentage calculations % Long tail Rabbits 2 4 7 10 Analysis: Calculate the percentage of each tail type using the following method: % Short tail rabbit (Short tail rabbits/Total rabbits) X 100 % Long tail rabbit -100% -% short tail rabbits. Q9. Briefly explain how this change in DNA affected the allele frequency of the population. Be sure to use your data in this explanation. Q10. Does the data in the table above support the hypothesis for this experiment? Be sure to use your data in an explanation of why the data does or does not support your hypothesis. I Discussion Questions: Use your data, your knowledge of evolution, and genetics to answer the questions that follow. Q11. Given the current definition of evolution being a change in allele frequency over time, did any of the mutations above fail to cause the population to evolve? If so which one? Use your data to explain how you know. Q12. Predict what would have happened in simulation 1 if you had switched the environment from equator to arctic. Do you think the brown rabbits could have been completely bred out of the population like the white ones may have been in simulation 1? Why or why not? Q13. In simulation three there should have been very little change in the percentage of each type of rabbit. Why did the allele frequencies not change as drastically in this simulation as they did in the other two? Q14. Compare your data from simulation 1 and simulation 2. In simulation 1 the mutation was recessive; in simulation 2 the mutation was dominant. What was different about how these two populations evolved after the mutation? Did being the dominant form of the trait insure that it would be selected for? Q15. The mutations you made were in reality small changes in the DNA. Briefly explain how a small change in DNA can cause such a huge evolutionary shift within a population. 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