Module 6 Lab- Morse

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Apr 3, 2024

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Name___________________________ Module 6 Lab Report Before you begin, read the related documents on exploring the issue and gaining an overview. Then go through each experiment and answer the questions. Please use complete sentences when answering questions. Answers in this lab are based on material studied in the lecture so you should read and study the lecture and complete the lecture assignment before doing the lab. Part 1: Greenhouse Experiment I. Observations To form a hypothesis about how color patterns in guppies evolve through natural selection, you start with the set of observations listed below.  There is variation among individuals of fish populations in body color patterns, with individuals exhibiting different spots of varying colors and sizes. In some fishes, the frequency of color pattern polymorphisms is correlated with the presence or absence of visually-directed predators.  Guppies show complex color pattern polymorphisms which vary greatly among individuals. Natural populations are so highly polymorphic that no two individuals look alike.  The patterns in guppies consist of spots or patches that vary in color, size, position, and reflectivity (iridescence). The patterns are genetically controlled but the color genes are only expressed in adult males.  Two opposing environmental factors influence color patterns: selection for being camouflaged against the background to avoid predation, and selection for conspicuousness to enhance sexual selection. This trade-off poses an evolutionary choice for guppy populations. Males need to be conspicuous enough to attract a mate but not so conspicuous as to be easily seen by a predator.  In order to be inconspicuous or camouflaged, the color pattern must blend with the background seen by the visually hunting predator. Any deviation from the background in pattern, color, or brightness will make a prey animal more conspicuous.  When predation and sexual selection occur together, a compromise in color patterning must be achieved to allow both survival and successful mating.  Guppy color patterns in natural populations show marked changes with predation intensity. The streams where guppies are found are often broken up with waterfalls up to 5 feet tall. These waterfalls isolate populations of guppies and of their predators. In isolated pond areas with the vicious guppy predator Crenicichla alta , male guppies have color patterns that more closely match the substrate surroundings. In isolated ponds with no predators or with a weak predator such as Rivulus hartii, male guppies are more colorful, standing out more against the background coloring. II. Hypothesis and Prediction Hypothesis The size, number, and color of the spots of male guppies are the result of interaction between the level of predation in each population and the need to attract females to mate. Prediction If predation on a guppy population is high, then a less conspicuous color pattern will be more prevalent in the population. If predation is low, then a more conspicuous color pattern will prevail in the population. III. Experimental Procedure These are the steps you will go through to carry out your experiment.  For the greenhouse experiments, construct 10 artificial ponds with sizes and shapes designed to mimic the natural environment of the guppies.

 Set up 4 ponds mimicking stream segments containing the strong guppy predator Crenicichla alta with dimensions of 2.4 x 1.2 meters with a depth of 40 cm. Add gravel of 6 mixed colors mimicking the substrate of natural streams (primarily black, white and green gravel with small amounts of red, blue and yellow).  Set up 6 other ponds with dimensions of 2.4 x 1.2 meters with a depth of 15 cm. Add gravel of 6 mixed colors mimicking the substrate of natural streams (mainly black, white, and green gravel with small amounts of red, blue and yellow). To 4 of these ponds add the very weak guppy predator Rivulus hartii and to the remaining 2 ponds add not predators.  Before adding the predators, establish a “foundation population” by rotating guppies between ponds for 6 months. This foundation population builds up genetic variability and reduces any founder effect that could influence results.  Add the predators to the appropriate pools after establishing the foundation population.  For the next 14 months examine the male fish for their colors. Score the fish based on the number, color, and size of spots. IV. Results Figure 1 V. Questions

1. What are the independent and dependent variables in this experiment? Refer back to the hypothesis and prediction if you are not sure. The independent variable is the amount/the presence of predators. The dependent variable is the size, number, and color of the spots on the male guppies. 2. What variables does the experimenter control for? Remember that control variables remain the same in all parts of the experiment and so should not affect the outcome. The control variable are the foundation populations, gravel color. 3. In your own words, describe the data shown in Figure 1, including numbers. Do not provide interpretation, just summarize the important trends in the data (do not list every data point, those can be seen from the graph). Describe how the number of spots changes over time in each of the 3 treatments, including the final numbers of spots. Several sentences will be required to do a good job on this question. There is a steady growth in the number of spots of the non-predation group throughout the experiment being shown in figure 1. They end up with 13 spots per fish, and the low-predation group increased until about 10 months where the changes start to level out. From 10 months on, that group stays just under 13 spots per fish. The high predation group increases until 6 months, where it then decrease throughout the rest of the experiment, ending at a little over 9 spots per fish. 4. Which two treatments have the most similar changes in spot numbers? The no and low predation treatments 5. Which treatment had the highest rate of change (the line with the greatest slope) after the 6 month foundation period? The high predation treatment has the highest rate of change after the 6 month foundation period. VI. Conclusions Here are 4 possible conclusions that one could draw from the results above. Address each possible conclusion and clearly state whether you accept it or reject it as a conclusion based on the data above. Then for each one, explain why you accepted or rejected it. Use actual data, i.e., numbers of spots, to support your answers. Use the analysis lines, not individual data points, to draw your conclusions. Some answers may come from the introductory readings. C1. Guppy populations from the high predation ponds ( C. alta ) initially responded by reducing the number of spots, but then spot number leveled off as the experiment continued. Rejected. After the 6 month foundation period, the spots is at about 12 spots per fish. That number goes down every month, reaching just over 9 spots at the end of the experiment. C2. Ponds with low predation ( R. hartii ) had results similar to the ponds with no predation. Accepted. Results were similar but not the same. The low predation increased spot number fast before leveling out to about 13 spots per fish. The spot number for no predation was rising more steadily and ended at about 13 spots per fish as well. C3. The male guppies in the high predation ponds were able to find mates even though they were relatively drab colored. Accepted. Relatively drab coloring is accepted as it is necessary to survive in high predation environments.

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C4. During the first six months of the experiment, when the foundation population was being established, the number of spots decreased slightly over what was present in the initial population. Rejected. During the time the foundation population was being established, all number of spots increased for all groups. The groups started at about 10 spots per fish at the start, and by the end of the trial all groups had about 12 spots per fish. There wasn’t a decrease in spot numbers during the first 6 months. VII. Discussion Questions In this section you are explaining why you got the results described above and analyzing, drawing conclusions, and extrapolating from the results. You are not reiterating your description of the results. For each of these questions, provide a thorough explanation of your thinking. 6. In your own words, explain why you believe that you got the data you got. Refer back to ideas or general principles discussed in the introductory material and remember that natural selection is based on who survives and who reproduces. There was more pressure on the high predators group to adapt. If they didn’t experience a decrease in spot numbers/colors, they would be easily noticed by predators and be killed before they could end up reproducing. Without the high levels of predation, guppies were able to keep and soon overtime, see an increase in the numbers/colors of spots as there was no danger. 7. Why were the results of all 3 treatments the same for the first 6 months of the experiment? Why (generally) did they change after that? I am asking about the experimental procedure here, not about the results of the experiment. The treatments were all the same to establish a foundation period to build up genetic variability and reduce any effects that could influence results. They changed after that because the populations were left alone from human control and left to reproduce in the new, genetically more variable populations that had been established. 8. What would you expect to see if you continued the experiment for another year? Why? If this continued for another year, we would expect to see some more changes in increases/decreases of spot numbers for low, no, high predation groups. I would then expect all the groups to start leveling out. 9. What do you think the microevolutionary effect on the guppies would be if you used gravel that was very colorful in another version of this experiment? Address each treatment separately (high predation, low predation, and no predation). High predation groups would most likely not be as drab as they were with the natural color gravels. The low predation group, and no predation groups would most likely see some changes, as while there is not a strong signgicant impact of their spot, color, number, they don’t all have to blend. 10. Why do you think that the no predation and low predation pools were so similar in their results? They would be similar because there is not a large threat for them to have less spots. They want to be flashy to get mates. 11. Do your results support or reject your hypothesis? Support

Part 2: Field Experiment I. Observations The beginning observations are the same as those for the greenhouse experiment. II. Hypothesis and Prediction Hypothesis The size, number, and color of the spots of male guppies are the result of interaction between the level of predation in each population and the need to attract females to mate. Prediction If predation on a guppy population is high, then a less conspicuous color pattern will be more prevalent in the population. If predation is low, then a more conspicuous color pattern will prevail in the population. III. Experimental Procedure  For the field experiment, identify an isolated pool in a stream that contains R. hartii but no guppies or C. alta .  Take about 200 guppies from a pool containing guppies and C. alta and score the male guppies for color patterns as above. Add these guppies to the pool with R. hartii .  After 15 generations, remove the guppies from the test pond and score the males for color patterns, specifically the number of black, blue and iridescent spots. IV. Results Figure 2

V. Questions 12. What are the independent and dependent variables for this experiment? One is a little different from that of the first experiment and the other one is the same. The dependent variable is the size, number, and color of the spots on male guppies. The independent variable is the type of predation/pool the guppies are in. 13. In your own words, describe this data. Do not provide any interpretation, just summarize the important trends in the data. The blue spots have the least amount in both predation groups, and the black spots were about the same. The low group has a high number of iridescent spots while the high predation group has a low amount of iridescent spots. VI. Conclusions Here are 4 possible conclusions that one could draw from the results above. Address each possible conclusion and clearly state whether you accept it or reject it as a conclusion based on the data above. Then for each one, explain why you accepted or rejected it. Use actual data, i.e., numbers of spots, to support your answers. Use the analysis lines, not individual data points, to draw your conclusions. Some answers may come from the introductory readings. C5. Although the substrates of the natural streams are somewhat colorful, they tend to be darker in overall color. Based on this, it is not surprising to see that the guppies in the high predation pool had more black spots than those in the low predation pool. Reject. Both predation level pools had almost 2 spots per fish C6. Although the low predation guppies had more colorful spots, the high predation guppies had more spots overall. Reject. The low predation group has about 7 spots/fish while the high predation group had about 4. C7. The larger numbers of blue and iridescent spots on the low predation guppies make them more conspicuous compared to their high predation counterparts which is better for attracting mates. Accept. Low predation guppies are going to attract more mates. They can do this because being conspicuous doesn’t attract predators, as there are none/not as much. High predation guppies blend in more to avoid predator attention. C8. Pressure from sexual selection causes the high predation guppies to have some blue and iridescent spots even though it makes them more conspicuous. Accept. The high predation have around 1 blue and black spot. This is the opposite to the low predation guppies who have about 2 blue and black spots. Them having bright spots allows them to avoid predation while still attracting some mates. VII. Discussion Questions In this section you are explaining why you got the results described above and analyzing, drawing conclusions, and extrapolating from the results. You are not reiterating your description of the results. For each of these questions, provide a thorough explanation of your thinking.

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14. In your own words, explain why you believe that you got the data you got. Refer back to ideas or general principles discussed in the introductory material and use the ideas of natural selection. It was achieved because low predation guppy pools didn’t need to blend in while the high predation guppy pools did. The meant that the low predation guppies could stand out a little more and get more mates. They could do this without being killed off before they can reproduce. 15. How well would the guppies from the high predation pool compete for mates if they were transferred to the low predation pool? Explain your answer. They wouldn’t compete at all. Low predation pool is brighter, more conspicuous, guppies would find more mates and reproduce quicker than others. Guppies from high predation pools have less spots and are therefore less impressive to the female guppies. 16. What do you think would happen to the guppies from the low predation pool if you transferred them to the high predation pool? Explain. The low predation guppies would be killed by predators very fast as they are much more noticeable than the less spotted. It would make it easier for the guppies in high predation pools because it would make them a little bit more noticeable, which would mean they are killed off quicker. 17. Would a new mutation causing guppies to develop large bright yellow spots be selected for or against in the two different streams? Explain why. This would work for guppies in the low predation pool because it would make them even more noticeable and attractive to mates as it is bright and new and unique. The would work against guppies in the high predation pool because it would make them more noticeable to predators, which leads to them being killed. 18. Do your results support or reject your hypothesis? Support

Module 6 Lab- Morse

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