Morgan Barrett Katie Eiden Allison Kasmiskie Sarah Scharpen

Transcription

1 Experimental Design: Race to the Finish Line Determining Whether the Size of a Container Affects the Growth Rate in a Monarch Larvae On our honor, we pledge that we have not given, received, nor tolerated others use of unauthorized aid in completing this work. Morgan Barrett Mbarret2@gustavus.edu Katie Eiden Keiden@gustavus.edu Allison Kasmiskie Akasmisk@gustavus.edu Sarah Scharpen Sscharpe@gustavus.edu EDU 246, Dr. Michele Koomen 10/31/2009

2 Abstract: Over the course of three weeks, our team reared and observed twenty Monarch larvae. The experiment was designed to determine whether or not the size of the container that a Monarch larva is raised in affects its rate of growth. Throughout the experiment our team observed the monarch larvae in various stages of life, measuring and recording their body mass and size. The last observation that we made was the exact date that they pupated. Each larva was placed individually into a clear plastic food container, of either _ pint, pint, quart or two quart size. Each larva was given a piece of common milkweed every day. We were successful in having eighteen of twenty Monarch larvae pupate. The experiments results showed that the size of the container did not affect the rate of growth or pupation. The larvae all pupated along the same timelines regardless of container size. Each member of the team housed larvae. The data might be undependable and inconclusive because the larvae were in different environments and were being handled very differently by each individual team member. The experiment started at the end of the milkweed season, causing the food supply to be very low and not of good quality. A more controlled environment could have produced a better, more realistic and reliable set of results in reference to the rate of growth and the size of container that a Monarch larva lives in. Seasonal timing should be considered when doing this type of experiment. Our experiment may not have been carried out during the optimal season due to the limited supply of food, the cool weather, and the larva s natural tendencies during this time of year. Introduction: During the month of September 2009, in Science for Elementary Educators class, Allison, Katie, Morgan, and Sarah each individually raised a Monarch butterfly from an early

3 staged larva to adulthood. After learning how to rear these Monarchs properly in class, we were curious to learn more about the Monarch s lifestyle and if different environmental conditions might affect how they matured. The question that we asked was, How do varying sizes of containers affect the growth rate of the Monarch larva? Our hypotheses were; H a1 : If the container is larger than the larva will be larger and grow at a faster rate. H a2 : If the container is larger, than the larva will be smaller and grow at a slower rate. H o : The size of the container will have zero affect on the rate of growth of the larva. Design and Methodology: Materials: 20 monarch caterpillar larvae 5x _ pint plastic deli container 5x 1 pint plastic deli container 5x 1 quart plastic deli container 5x 2 quart plastic deli container Scissors Large supply of common milkweed 15x _ pint circular paper towel liner 15x 1 pint circular paper towel liner 15x 1 quart circular paper towel liner 15x 2 quart circular paper towel liner Ruler (metric) Scale (.001 gram) Notebook Pen/pencil

4 The project team consisted of four group members. Three of the four group members received four monarch larvae of approximately the same size and age. The fourth group member received eight monarch larvae approximately the same size and age. Each group member then received one _ pint container, one pint container, one quart container (the control size), and one 2 quart container. The fourth group member who received eight larvae received two of each different container. A pair of scissors was then used to puncture several small holes into each of the container lids. The containers were then lined with a paper towel specifically cut and moistened to fit each container size. A single leaf of fresh common milkweed was placed in each container followed by one of the twenty monarch larvae. The containers were then sealed and each group member brought her charges home. Each group member was to place the containers holding the monarch larvae in an area inside her room that received moderate amounts of light throughout the day. The temperature of the room that held the monarch larvae remained at a relatively consistent 65 o Farenheit. The containers were to remain clean. Each day the frass from the containers was to be removed to promote the health of the monarch larvae. The caterpillars were to be given one common milkweed leaf at a time. The milkweed would only be changed out if it was fully consumed or began to dry out. When the paper towel liner of each container began to appear dry/soiled, it would be replaced with another moistened paper towel liner cut to size. Two different forms of measurement were used to document the growth of the monarch larvae. Each group member was to use a metric ruler and measure the length and width of a caterpillar s body when positioned in a straight line. The measurements were documented in millimeters every Monday, Wednesday, and Friday. The monarch larvae were also weighed every Monday and Friday using a scale that was accurate to the.001 gram. The information 4 P a g e

5 collected was then recorded onto a table in a notebook. Each member was to collect information of the weight and size of her charges from Wednesday, September 30 th to Wednesday, October 21 st. This gave sufficient time to document the changes that occurred in the caterpillars during the experiment. Results: L = Length in centimeters W = Width in centimeters m = mass in grams - = the larva is pupating D = the larva has died 5 P a g e

6 _ Pint A L: 1.2 W:0.2 _ Pint B L: 1.3 W:0.2 _ Pint C L: 1.5 W:0.2 Control- 1Quart A Control- 1 Quart B 6 Control- P a g e 1 Quart L: 2.2 W: 0.3 m:.244 L: 3.5 m:.759 L: 2.2 W: 0.3 m:.264 _ Pint D L: 2.5 m:.264 _ Pint E L: 1.4 W:0.2 Pint A L: 2.0 W:0.3 Pint B L: 1.3 W:0.2 Pint C L: 2.2 W:0.3 Pint D L: 2.2 W:0.4 Pint E L: 1.4 W:0.2 2 Quart A 2 Quart B 2 Quart C 2 Quart D 2 Quart E L: 2.0 W:0.3 L: 2.1 W:0.3 L: 2.2 W:0.4 L: 1.8 W:0.3 L: 2.0 W:0.3 L: 2.4 W:0.4 L: 1.5 W:0.2 L: 2.2 W:0.3 L: 1.6 W: 0.2 m:.062 L: 2.4 m:.239 L: 3.2 m:.517 L: 3.3 m:.418 L: 2.2 m:.198 L: 1.9 W: 0.3 m:.128 L: 3.0 m:.393 L: 3.3 m:.624 L: 2.7 m:.308 L: 2.1 m:.235 L: 2.4 W: 0.3 m:.286 L: 3.0 m:.467 L: 2.5 W: 0.3 m:.194 L: 2.7 L: 3.3 m:.832 L: 3.0 W: 0.7 m:pupae L: 2.9 m:.505 L: 2.8 m:.436 L: 2.0 W: 0.3 m:.142 L: 4.1 m:1.142 L: 4.3 W: 0.8 m:1.414 L: 4.2 W: 0.7 M:1.385 L: 2.3 m:.254 L: 2.2 m:.275 L: 5.0 W: 0.7 m:1.414 L: 4.2 m:1.321 L: 4.0 W: 0.8 m:1.292 L: 2.4 m:.259 L: 3.1 m:.429 L: 4.5 W: 0.7 m:1.472 L: 4.0 m:.973 L: 4.0 W: L: 4.2 W: L: 3.3 W:0.5 L: 2.2 W:0.4 L: 3.9 m:1.291 L: 2.5 m:.265 L: 4.8 m:1.586 L: 3.2 M: L: 3.7 W:0.6 L: 3.9 m:.937 L: 4.2 W: 0.7 m:1.126 D D D D D D L: 3.0 W:0.5 L: 2.7 W:0.5 L: 3.7 m:1.043 L: 2.9 m:.496 L: 4.5 m:1.387 L: 3.3 m: L: 3.6 W:0.7 L:4.0 W:.8 m: L: 2.9 W:0.5 L: 3.7 W:0.7 L: 3.6 m:1.046 L: 4.0 W: 0.7 m:1.230 L: 4.8 m:1.578 L: 4.3 W: 0.7 m:1.281 L: 5.3 W: D D D D D D L: 4.3 W: L: 3.7 W:

7 Growth Rates _ pint: Length Width Mass Mean cm Mean- 0.1 cm Mean g Median cm Median- 0.1 cm Median g Mode- 0.7 cm Mode- 0 and 0.1 cm Mode- none Range cm Range cm Range g Pint: Length Width Mass Mean cm Mean cm Mean g Median- 0.5 cm Median- 0.1 cm Median g Mode- 0.4 cm Mode- 0.1 cm Mode- none Range cm Range cm Range g 2 Quart: Length Width Mass Mean cm Mean cm Mean g Median- 0.6 cm Median- 0.1 cm Median g Mode-.3 cm Mode- 0 and 0.1 cm Mode- none Range cm Range cm Range g 7 P a g e

8 Control (1 Quart): Length Width Mass Mean cm Mean cm Mean g Median cm Median- 0.1 cm Median g Mode-0.3 cm Mode- 0.1 cm Mode- none Range cm Range cm Range g Interpretation and Discussion: Looking at the data collected throughout the experiment, our group has determined that the size of the container does not significantly affect the growth of the monarch larvae. During observation, we noticed that for the majority of the larvae, there was a consistent rate of growth in both the length and width. The overall weight of the caterpillars fluctuated due to the fact that the caterpillars were not all the same size when first collected. Little research as we are aware of has been done on the size of the environment of the monarch larvae and its affect on the growth of the larvae. What research there is has produced mixed results. This experiment has shown us that while the size of the containing environment does little to affect the growth of the caterpillars, other factors may play a role in the rate of development of monarch larvae. As future teachers, we believe much knowledge can be taken from this experience. We have worked through an experimental design and discovered that what we believed to be true may, in fact, be wrong. By understanding how to create an experimental design, we are more capable of creating effective projects for our students. Step by step method plans are key in ensuring that any data collected during an experiment is as accurate as possible. By going through the process of creating an experiment ourselves, we believe we can help students create their own experiments with accuracy and efficiency. 8 P a g e

9 Implications for future work If we were to research this topic again, we would alter a few aspects of our experiment. Overall, we would use a larger population size of caterpillars, to better represent the actual population. Initially, we would make sure the caterpillars are all the same size, or about the same size when beginning the experiment to make our results as accurate as possible. Also, we would adjust the container sizes so that the smallest container would be a pint instead of a half pint. Along with that change, we would add additional container sizes to give the caterpillars a larger environment in which to grow, simulating the large space of their natural environment. We would even take this study a step further and see if there is a difference in growth rates of raising caterpillars indoors and outdoors, in their natural habitat. To ensure that all the caterpillars have the same surroundings, we would raise all of them in the same room to rid of some confounding variables we had in our original experiment. Lastly, we would make sure we undergo our research in a warm season so that if the caterpillars were to be studied outside, they will not freeze, and so that the butterflies can be released. As a group we reflected on how we can improve our experiment, and it is our belief that these changes will provide researchers with accurate results. In doing this experiment, we learned about the experimental process. We were forced to think about all possible variables that would affect our experiment, and try to control those variables equally, as a group, in order to have the most accurate results. In addition, we learned about the need for a control in an experiment. Also, we learned how to gather and formulate results, as well as analyze them. We now have the ability to identify variables as well as reflect 9 P a g e

10 and even understand how they affected our experiment. Based on those reflections, we were able to learn from our mistakes, and reflect on changes if we were to do the experiment again in the future. All of these skills allowed us to further our learning and bridge it over to teaching. Our group has the ability to teach students ways in which they can investigate questions and solve problems. In addition, we can now teach students about the lifecycle of monarch butterflies. Some of us even got the chance to see the caterpillars pupate, and/or emerge from their chrysalis as a butterfly, which are events we can someday bring into the classroom in raising our own monarchs. Limitations of our experiment As with all experiments, there were many confounding variables that may have influenced our own. The key factor is being able to identify these variables. We broke down our variables into two categories: environment and milkweed. The variables that affected the caterpillar s overall environment are cleanliness of containers, light, surrounding noise and temperature. A lack of cleanliness resulted in death to some of our caterpillars. In regards to light, caterpillars do need a sufficient amount, but not a lot of light. We factored in the surrounding noise they heard in their environments, such as music and talking, and decided that those may also have affected their growth rates, but are not sure whether or not this holds true. Lastly, we realized that the temperature in each of the environments was probably different based on the location of the room and whether it had lots of windows, or the heat on, which also could have affected growth. Our second category, milkweed, was broken down into two parts: size and quality. In our experiment, each caterpillar was to receive only one leaf a day. All leaves were not the same size, and so the size of leaves may have affected growth rates. As a 10 P a g e

11 group, we tried our best to control variables that allowed us to do so, but not all variables could be controlled based on the design of our experiment. In doing our experiment, we found that there were several limitations of our actual experimental design process. Our sample size was limiting because we only raised twenty caterpillars; using a larger sample size would have better represented the actual population. The sizes we chose for our containers were also limiting for two reasons: one, there was not enough room for the monarch to emerge from its chrysalis and dry its wings, and two, we could have used more container sizes for the same reasons as having a larger sample size. The initial sizes of our caterpillars were also an issue at the beginning of our experiment because they were not all the same size, or even about the same size. Some were much smaller than others when we began our experiment, and this may have affected accuracy. Another limiting factor was the different environments that we raised them in. Each group member raised four to eight caterpillars in her room, which resulted in four different environments. These different surroundings may have affected the growth rates of the caterpillars as each room had varied amounts of light, temperatures and noise. Transportation of caterpillars was another limiting factor because our group needed to transport the caterpillars to and from our rooms to weigh them, moving them from warmer to much cooler temperatures. The overall movement that occurred as we transported them from place to place may have also been a factor in their growth. Finally, the time of year we did our study was also a limiting factor of our experiment. Because the weather is getting colder, the quality of our milkweed was lower due to the cold, and our overall supply decreased due to freezing temperatures. Also, we were unable to release monarchs due to the cold weather, which means that they need to be stored until next spring when the weather will be suitable for them to be released. Our experimental design could be 11 P a g e

12 changed in the future to eliminate some of, if not all of the limitations of our experimental design. Connecting the Nature of Science to your experiment: First, we were put into groups because science is believed to be a social activity. We were also allowed to pick our own topic because this reflects our society s view that responsibility is important for young adults to learn. Scientists believe that the world is understandable. According to the Nature of Science, the basic rules are the same everywhere (American Association, p. 8). Our group first brainstormed ideas that we would like to better understand. We wanted to further understand the effect that container/environment size would have on the growth rate of Monarch caterpillars. We knew that there was already scientific evidence about the size of other animals in certain size cages but were unsure of the effect it would have on caterpillars. Scientists use already established theories and works to make predictions, so using those theories and logic we predicted that the size of the container would be directly proportional to the caterpillars growth rate and size. In order for our experiment to be truly scientific, we obtained evidence to support our predictions. However, through this experience, our group also learned the scientific world view that science cannot offer complete answers. By the end of 5 th grade, students should already know that different studies rarely turn out exactly the same (American Association, p. 6). Although it seemed to have an effect on other animals, the larvae growth rate and size was unaffected by the size of the container. It was important to figure out why our predictions were wrong. Our group brainstormed and thought that this may have been due to small differences in rearing by each of the group members and even uncontrollable differences such as temperature. Therefore, we were also taught another nature of science: it is important to obtain accurate and careful data 12 P a g e

13 (American Association, p. 10). Having precise and accurate data leaves little room for questioning. Conclusions and Acknowledgements: At the conclusion of this experiment, we learned that the size of the caterpillar s environment does not affect its growth rate, although there were multiple confounding variables. In reflecting on the experiment though, we realized we have learned how to approach the scientific method. With this, we ultimately learned how to teach this method to students, helping them to understand that their results may be affected by multiple variables, like in our own experiment, and how to alter their experiments to eliminate such variables. We would like to acknowledge, Michael Koomen, for providing us with monarch larvae and milkweed needed for our experiment, and thank her for reviewing and commenting on our experimental design. Overall, this experiment has taught us to expect the unexpected, improve variables to deal with the unexpected in the future, and has given us the ability to teach these concepts to our future students. References: American Association for the Advancement of Science. (1989). Project 2061: science for all Americans. Washington, DC: Author. Bohlen et. al. (2008). Monarchs: Light vs. Dark Conditions Affect on Rate of Growth. St. Peter, MN. Brace et. al. (2007). Monarchs and Melon Preference. St. Peter, MN. Hillman et. al. (2007). Experimental Design Correlation between the Size of Larva and Size of Adult Monarch Butterflies. St. Peter, MN. 13 P a g e

14 Michele Koomen, Ph.D. Co-Chair and Assistant Professor Education. Oberhauser and Goehring. (1997). Monarchs in the Classroom: An Inquiry-based Curriculum for Middle School. St. Paul, MN: University of Minnesota. 14 P a g e