Feeding Methods Of Larvae:

Transcription

1 Feeding Methods Of Larvae: Differences in Caterpillar Growth Due to Differences in Food Distribution On our honor, we pledge that we have not given or received or tolerated others use of unauthorized aid in completing this work. Heidi Rossow Kyle Tarbutton Megan Lieser Sarah Eide EDU 246 Dr. Michele Koomen 10/31/09 1

2 Abstract: Four weeks ago, we started out with a plan to rear twenty larvae and attempt to discover if larvae that were given consistently three leaves at a time grew more rapidly in comparison to those that were fed solely one leaf at a time. Throughout the following weeks, we would track the larvae s leaf consumption by measuring out the amount of leaves that remained after consumption. Each larvae was placed into a plastic container that mimicked the containers of the other nineteen larvae. All of the larvae were placed in the same environment on a bookshelf in the Mattson Hall with temperatures and lighting that were exactly the same. Every day, one member of the group would return to Mattson Hall, measure out the remaining leaves to find the amount of consumed leaves from each individual larvae by using the scale provided, replacing leaves that were molding or almost gone, and replacing the larvae back on their bookshelf. The purpose of this experiment was to discover if larvae that were offered more food, in this case three leaves at a time, would consume more in comparison to larvae that were fed only one leaf at a time. By going through this experimental process, we were allowed a hands on approach to hypothesizing, conducting, and drawing conclusions from a valuable experimental design. Slowly, as the week passed on, our larvae began to die off. The reason for this unexpected death can only be hypothesized, as the dead larvae were disposed of immediately after their death was discovered. When looking at certainties, we know that same size containers were used for 2

3 all of the twenty larvae, that the water used to moisten the filter paper was from the same spray bottle, that the filter paper was all the same, and that the source of the milkweed was the same for all of our larvae. Throughout this process, we have learned that the food containers used for housing the larvae could have potentially been carrying some contamination, which leads us to question the food containers that we receive our own consumer good products in. Something else that amazed us was the fact that monarchs have the ability to fly south, through damaging weather and predators, and still survive, yet our larvae were given essentially perfect living conditions and yet died off. Introduction: Our idea for our experiment came from our own different observations during the time when we were rearing monarchs. When we were first discussing different research topics, we commented on the activity level of monarchs. We thought about doing a project based on this; however we noticed a couple people in our class were already pursuing that idea. Another idea that we had was to use different milkweed, but again other people were pursuing that idea as well. We then started talking about other things that we noticed when we were rearing our monarchs. We all commented on how much food they eat as they grew. We all noticed how they eat so little when they are little, but when they get bigger they eat a leaf a day or more. This piqued our interested, and brought us to our decision to research different feeding methods of monarchs. 3

4 Our research question is how does the amount of food with common milkweed affect the caterpillar s growth? We had 3 hypotheses for this experiment. HA1- The amount of food given to the caterpillar will affect its growth. HA2- The caterpillar will die, because it doesn t know when to stop eating. Ho- The amount of food given to the caterpillar won t affect its growth. Design and Methodology: We began our experiment with twenty monarchs, which were in their larvae stage. We decided as a group on twenty larvae, so that we could obtain a control group and an experimental group. We observed and recorded the masses of leaves that all of these twenty monarchs ate. The materials that we needed for our experiment were 20 larvae stage caterpillars, 20 large containers that the monarchs were kept in, Common Milkweed, filter paper for each of the containers, and a scale for massing. Our instructor, Michele Koomen, provided all of these materials for us. The things that stayed constant in our experiment were the same type and brand of containers for all the monarchs. We also used the same milkweed, which was Common, and put the monarchs in the same environment. They were put on a bookshelf in the curriculum lab in Mattson Hall. We collected the mass of food eaten everyday and then recorded those findings. We had two groups for our experiment; we had a control and an experiment group. Our control group was given 1 leaf at a time until it was eaten. Our experimental group was given 3 leaves at a time until one was fully eaten. We first recorded our results on a piece of paper and then eventually transferred it onto an excel 4

5 spreadsheet, which was updated daily. All of the results were recorded in grams. Results: By calculating the control group mean, median, and mode of how much the caterpillars ate we came up with the following information. The mean is.129 grams, while the median is.093 grams, and the mode is.093 grams. On the experimental group the mean that was calculated was.169 grams, the median is.141 grams and the mode is.059,.126. Appendix A has the table of every day calculation. Interpretation and Discussion: Monarch butterflies face many challenges while making their trip from the northern part of North America down to Mexico for the summer. Many different species of birds pick out monarchs for a quick meal that could include sparrows, cardinals, and robins. Parasites such as the tachinid fly kill the monarch from the inside out before it ever has a chance to spread its wings. The protozoan Ophryocystis elektroscirrha can also be extremely hazardous to a monarch, since it is so easily spread from butterfly to plants to more butterflies. Because our monarchs were in small, decontaminated, containers, none of these usual suspects can be linked to the demise of all 20 of our monarchs. As future teachers, we took it upon ourselves to discover the culprit that mercilessly killed our monarchs. 5

6 Since monarchs are cold-blooded animals, they avoid cold weather like the plague. This is of course their prime reason for flying south for the winter. Only a few days after we began our experiment, the weather outside became so cold that it snowed. Even though the monarchs were inside, they were very close to a window, and the freeze was unexpected, so it is likely the heat inside the building was not turned on. About a week or to into the experiment, all four experimenters noted an excessive amount of mold on a great number of leaves that were home to our monarchs. There was mold in nearly every single one of the containers. Some monarchs were dead as soon as the mold was present, while others seemed to be unaffected. I found this death by way of mold most similar to the experiment Dr. Co-Chair Michelle Koomen showed us concerning the effects of pesticides on monarchs. Both cases had a 100% mortality rate, and all fatalities occurred before the monarchs pupated. Implications for future work: Our group learned that once you do an experiment it might not go the exact way that you may have planed it to. The group was very excited to see how things would turn out by having twenty caterpillars to observe on a daily basis. Once days started to pass we started to realize that something was wrong with our caterpillars because they all started to die. We knew we had to keep going and hoping for good results with the rest of the caterpillars but learned as days continued to pass more and more caterpillars were dying. 6

7 For future work we think that we could have add another twenty caterpillars in containers just to see if something was wrong with the containers or if it was something else. It would also be interesting to see if it would have made a difference if we put about three caterpillars in one container. This could possibly have made the caterpillars survive or at least some of them. Another idea would have been to make sure the containers we were using were sanitized well because that is a main reason why we think the caterpillars died. If the materials are not clean it definitely become a major problem in an experiment. As a group if any students would want to extend this experiment it would be a good idea to start out with more caterpillars because in our case all of them died but if there were more to begin with there could possibly have been more results to get an accurate reading. Another possibility would be having a few caterpillars that had one leaf along with some that had two leafs and then a few caterpillars with three leafs instead of one and three leaves which was our experiment. This could potentially show an actual outcome considering with our data we don t have much to go off. Our design of the experiment was well planned out with exactly what we were going to do and what we were looking for in the end. If the caterpillars would have survived it possibly could have been a great experiment. We think that there was something in the material of the plastic containers we used because not only did it cause the caterpillars to die it also caused the milkweed to mold everyday. 7

8 Some things that our group learned was the fact that time management is very important when it comes to doing an experiment. We all had to figure out when would work best for someone to go check on the caterpillars and way the mass of the milkweed leaves. Sometimes it was difficult for someone to go because all of our group members were very busy but with careful planning we always managed to have someone go. Another important lesson we learned was when you hope for a specific result it might not always happen. In our case we really hoped for an accurate result of the experiment but in the end we didn t manage to conclude anything because all of the caterpillars died. By doing this experiment it definitely shows ways that we can become better as a future teacher. It is a good example to let our future students know that it is okay to fail because you only can learn from those experiences. Especially when it comes to science things may not go the way planned and you have to alter those planes. Limitations of your experiment: Because our experiment was on the smaller scale and we weren't presented with as many variable options as we could have been, there were a few pieces to our puzzle that limited our experiment. For starters, the plastic containers in which we housed our twenty caterpillars appeared clean to the human eye, but in reality, we believed to be contaminated. Professor Michele Koomen used similar containers for her personal monarch farm, and she claimed that many of her caterpillars were dying off as well. Had we began the experiment with completely clean containers, it is possible that more of 8

9 our experimental and control group caterpillars would have survived. Another limitation to our experiment was the retrieval of data and timing selected each day for this retrieval. Due to the extremely busy schedules of our four group members, it was decided that one person would collect data each day, but it wasn't always at the exact same time each day as had been requested at the beginning of the experiment. A third limitation to our design was the mass death of our caterpillars. As caterpillars started dying, our data became skewed until there was no data at all. Had our caterpillars survived, the entire experiment and our hypothesis could still have turned out to be successful. A limitation that should have been thought out more carefully is the relatively small sample size used for this experiment. Originally, twenty caterpillars had seemed like an appropriate number for our experimental design; ten for the experimental group and ten for the control group. In hindsight, it appears that more than twenty caterpillars would have made observations about our data easier, and a more concise conclusion could have been determined. A fifth limitation that has been discovered is the selection of milkweed for the caterpillars; some caterpillars may have been given leaves that were deemed large while others were given a leaf that was deemed small. There was no set weight range for leaves, so although we massed out the leaves, we weren't one hundred percent identical from caterpillar to caterpillar. A final limitation to our experimental design was the shifting seasons and the frigid weather. Although the temperatures inside the classroom were set at a comfortable seventy degrees, the caterpillars were 9

10 placed on a bookshelf near a window, which could have impacted the temperatures near the caterpillars, which in turn might have affected their environments and growth. As can be seen from these limitations, the experimental design for our group was carefully thought out, but a few elements could have been tweaked to make this design more efficient and accurate. Connecting the Nature of Science to your experiment: The Nature of Science mentions key concepts that are believed by scientists and experimenters across the world, which can be used to explain natural phenomena from the elementary to graduate level. These concepts can also be applied to the research and experiment carried out by our group. One key concept is that the world is understandable. By carrying out our experiment with success, we would have seen the consistent patterns that occur throughout all of nature. This concept also is applicable to our experiment in that rules are the same across the board; this means all experimental larvae would have reacted one way while all the control larvae responded a different way. The Nature of Science states that scientific ideas are subject to change, which is evident in our experiment by changing hypothesies throughout the experiment due to challenging data and observations. Our experiment is connected to the Nature of Science with the belief that ideas can be modified without being put on the chopping block. According to the Nature of Science, scientists and experimenters have a strong faith in accurate data, and because of the mass death throughout our 10

11 experiment, sufficient data was not obtained. By making predictions and allowing our theories to be adjusted, our experiment was comparable to the Nature of Science concept of explanation and prediction. Lastly, the Nature of Science holds the belief that science is a complex social activity, and this was verified through the various ways in which our group members interacted. Conclusion: With a combination of curious minds and observational attitudes, our group set out to observe the feeding methods of twenty differing larvae. As a requirement for the Science for Elementary Educators I class, we chose feeding methods as an interesting topic of study. By feeding ten larvae one leaf consistently while feeding the other ten larvae three leaves consistently, we hoped to see if larvae that were fed three leaves would grow faster than larvae that were fed solely one leaf. For reasons unknown, the entire population died. With many hypothesies in mind, our group believes the death is due mainly to an excessive amount of mold located on the common milkweed fed to the larvae. Implications brainstormed by the group were that a larger sample size would have been more beneficial or creating an experimental situation where larvae were fed one, two, and three leaves. We would like to acknowledge Dr. Michele Koomen for her provision of materials used in our experiment and her encouragement of our curiosity. The group would also like to acknowledge the Education Department of Gustavus Adolphus that allowed us the use of Mattson Hall and the necessary instruments used for weighing the 11

12 larvae. Lastly, we would like to acknowledge our parents for their continued support and inspiration throughout our lives. 12

13 Works Cited American Association for the Advancement of Science. (1989). Project 2061: science for all Americans. Washington, DC: Author. "Biology : Predation : Ophryocyctis elektroscirrha." Monarch Watch. Web. 29 Oct < 13