Hands-On Lab: Happy Worms Company

Transcription

1 Hands-On Lab: Happy Worms Company Summary In this activity, students investigate the ideal environment for a worm by experimenting with worm responses to light, heat, and moisture. Time Needed Preparation time: 15 minutes Activity Time: minutes Analysis Time: 20 minutes Extension: ongoing vermicomposting (using worms to compost organic material) Objectives After completing the activity and participating in discussion, students will be able to: Identify a valid testable question about worm behavior. Ask a valid scientific question about worm behavior. Make a valid hypothesis about the effects of one variable on worm behavior. Test a single variable at a time (light/dark, dry/moist, or cool/warm) while keeping all other conditions constant. Make accurate qualitative (e.g., How are the worms acting?) and quantitative observations (e.g., How many worms are in each area?) about the worms. Make an appropriate and accurate graph of the independent variable (the variable being tested) versus the dependent variable (number of worms on each side). Explain how at least one variable affects worm behavior. Relate the results of the investigation to the Happy Worms Company and propose a list of suggestions to the owner. Identify problems with the investigation and propose modifications to improve the investigation. Materials List (for each group) earthworms (Lumbricus terrestris) or redworms (Eisenia fetida): 15 per group (divide the worms into three groups so that each group of worms can rest between trials) small containers to carry worms (plastic lids work well) shoebox with lid wax paper (to line bottom of shoebox) cotton swab (to handle worms) timer or classroom clock Student Planning, Record, and Analysis Sheets Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 1 of 10

2 Variable: light dark construction paper scissors Variable: moisture two pieces of paper towel water Variable: heat two resealable sandwich bags paper towel water thermometer (optional) Disposal Information/Safety Alert Both earthworms and redworms can be used in the classroom for a period of a few weeks. Redworms are able to handle higher temperatures (up to 77 F) than are earthworms (around 60 F), so redworms might be a better choice. You can also use the redworms to start vermicomposting in your classroom. If you prefer just to dispose of the organisms, place them in a plastic bag, freeze them for 24 hours, and then dispose of them in the trash. This process ensures that you do not release potentially invasive species into your local environment. Be aware that some students may have a significant negative psychological reaction to worms. If students do not want to touch the worms, allow them to use moistened cotton swabs to move the worms. Preparation Decide how many groups you will have. Ideally, there are 2 4 students in each group and there is at least one group for each variable. Redworms are readily available from vermicomposting supply stores. Earthworms are available as bait. Both can be ordered from online suppliers. Both types of worms can be stored in a refrigerator until needed. Be sure that the material the worms are living in is kept damp (about as damp as a wrung-out sponge). Ideally, the teacher will provide 15 worms per group. However, 50 worms will do for a class of 30. Just be sure to allow worms a rest time before they are used in another trial. If you are doing multiple classes, the worms can be used again, and you will not need to buy additional worms for additional classes. Background Information for Teachers Worms are invertebrates with relatively well-developed nervous and digestive systems. Worms can sense temperature, light, and water. In general, worms prefer cool, moist conditions and darkness. With their muscular digestive systems, worms grind the organic material they take in for food into much smaller pieces and then release worm castings (or vermicompost). These castings can improve Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 2 of 10

3 the quality of soil, helping plants grow. As worms move through the soil, they break up soil clumps and leave behind small tunnels, which allow plant roots to reach into the soil more easily. Worms breathe air through their skin, which must be kept moist for this to occur. Too much water, however, is not good for them. Engage Read the following scenario aloud to the students while they follow along. Discuss the scenario with students and have them take notes on their handouts. (Note: if a similar actual scenario that students can relate to exists, present that instead.) Happy Worms Company Worms are unsung heroes of the environment. They eat organic waste and make soil richer, which allows plants to grow better. A young businessperson wants to start a business called Happy Worms Company, which will provide worms to sell to home gardeners. She has several places where she can grow her worms: in a dark basement, a bright sunroom, a cool area, and a warmer area. She also wants to know if she needs to keep them dry or moist. What will you tell her so that she can grow happy worms? Introduce the terms stimulus and response. A stimulus is a change in the environment (e.g., light or dark) and a response is what the organism does because of this change (e.g., the worm might move to a more comfortable area). Assess Preconceptions and Activate Prior Knowledge: Discuss with the class what they know about worms. Do they bite? How can you tell the front end from the back? What do they eat? Why are they good for soil? What conditions do you think worms live in best? You might wish to use a KWL chart to capture this information and return to it later. If students have little or no experience with worms, you might wish to give them time to observe the worms on their own for 5 10 minutes. Students should record their general observations about the worms as they observe them. Encourage students to think about what kinds of behaviors they see the worms performing. Have them consider what kind of habitat a worm would prefer. Discuss Safety: All students should wash and rinse their hands well before the activity begins. This protects the worms from germs the students might have on their hands. Hands will need to be washed well after the activity to wash away any germs the students might have acquired. If using alcohol based hand sanitizers, make sure that hands are completely dry and no alcohol comes in contact with the worms. Worms need to be handled gently, slowly, and sensitively, as they are living organisms. If needed, demonstrate appropriate handling of the worms, both with hands and with moist cotton swabs. Introduce the Activity: Explain to students that they will be investigating how the amount of light, amount of water, and temperature affect worm behavior. Have each group decide which variable they want to test. Discuss the concept of controls. Make sure students understand that in order to fairly test the effect of the one variable, everything else must be the same in each trial. For example, if they are testing the effects of light, the moisture and temperature must be kept constant. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 3 of 10

4 Explore Have students work in groups of 2 4 depending on supplies. Have each group use their Student Planning Worksheet to develop a plan for their investigation. The plans should clearly define: the question they want to answer the controlled and manipulated their hypothesis variables 1. Have each group set up a shoebox. Cut wax paper to fit inside the bottom of the box. Measure a line up the side of the box, on both sides, to show the halfway mark on the box. 2. Set up the experiment based on the variable chosen. Light versus Dark: Students will take a piece of dark construction paper, cut it to cover half the shoebox and to fit inside the shoebox, with 4 cm extra so that folds can be made to support the paper 2 cm higher than the bottom of the shoebox. This allows the worms to go into the shaded part of the box without touching the paper. Moist versus Dry: Students will place two pieces of paper towel in the bottom of the shoebox (lined with wax paper). One paper towel will be moistened, and the other will be dry. Be sure that the worms are placed with half of their bodies on each side for each experiment. Warm versus Cool: Students will use two resealable sandwich bags. One will be half-filled with cool water, while the other is half-filled with warm water. Make sure that bags lay flat on the bottom of the shoebox and can lie as close together as possible so that the worms don t have to climb a hill to get to one side or the other. Students should put one moist paper towel across the two bags. Thermometers are optional if you wish students to quantify warm and cool more precisely. 3. One group member should go get the five worms in the plastic lid. 4. Another group member should carefully place the worms so that one half of the body is on one side of the box and the other side of the body is on the opposite side of the box. This does not have to be perfect, as the worms will move. Another option is to pick up all three worms and place them in a pile in the center. Use the lines along the side of the box for alignment. 5. Use the lid of the shoebox to cover the entire experiment UNLESS the experiment is with light and dark. Try to keep the classroom quiet. Use the classroom clock or a timer to determine when 5 minutes has passed. 6. Take the lid off the box (if needed) and record where worms are located in the box. 7. Remove the worms from the shoebox, place them in the plastic lid, and return them to the teacher. Get a new set of five worms and return to the group. 8. Repeat steps 3 8, recording the number of worms in each area for each trial. Repeat again for a total of three trials with 15 different worms. As students are conducting their investigations, make sure each group is doing the following, providing support where necessary: Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 4 of 10

5 testing a single variable (e.g., temperature, moisture, light conditions), holding other conditions constant collecting and recording data accurately on the Student Record Sheet making qualitative (e.g., what the worms are doing) as well as quantitative (e.g., how many worms are found in each area) observations making observations regarding the design of the investigation as well as the results of the investigation thinking about how the investigation relates to the Happy Worms Company scenario After students have observed the first round of the worms' behavior, ask: "What is the difference between an instinct and a learned behavior?" Have students share their ideas and give several examples. Supplement with your own examples if necessary. For example, baby chimps have an instinct to hang on to their parents' fur as soon as they are born, however they must be taught by their parents how to use sticks to gather ants to eat. Explain also that some behaviors may be learned by experience: an animal that eats a nasty tasting butterfly will not eat that type of butterfly again. Ask: "Do you think that the movement of the worms is an instinct or a learned behavior?" Have students continue thinking about this question as they begin the next rounds of observations. Students may suggest watching how long it takes the worms to move away from things they don't like or toward things they do like as evidence. Explain 1. Have groups present their data and spend some time discussing the results with each other. How did each variable affect the worms? Which conditions did the worms seem to prefer? (Dark, cool, and moist should have been the preferred results.) Have students complete the Student Analysis Sheet and construct bar graphs of their data. Structured Option: Guide students with the graphing or simply have them make qualitative assessments of the data without graphing. Open Option: Have students build their graphs from scratch, deciding on the appropriate type of graph to use. 2. Bring the class back together so that they can share results and explain their results. 3. Apply to the Problem: Read the scenario to the class again. Have students use what they learned to determine which set of conditions the Happy Worms Company should choose to raise worms. Have students suggest what conditions the Happy Worms Company should watch carefully (e.g., cool but not too cold, moist but not too moist). Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 5 of 10

6 Elaborate/Extend Investigate the variables at different values. For example, change the amount of light, amount of moisture, or specific temperature of the water in the bags. Encourage students to find the optimum (best) values for each variable. Discuss real world uses for redworms. In addition to fishing bait, redworms are used in vermicomposting. Provide students with the opportunity to research how vermicomposting uses worms to convert newspaper and table scraps into rich organic compost for gardening. How can what students learned from the hands-on investigation apply to setting up a vermicomposting bin? Evaluate 1. Have students evaluate their investigation. Did the investigation help answer their questions? What about the design worked well? What didn t work well? How might they change the design in the future? (e.g., there conditions might not have been different enough, there might not have been enough time, they could have used more worms) What didn t the investigation tell them? What other variables could they test? (did not tell them if worms show preference for different conditions at different times - such as night or under different circumstances) How was the model like real life? How was it different? How could they make it more like real life? (there are many other variables that affect worms - food supply, time of day, type of soil, etc.) 2. Use the Rubric to evaluate students progress toward achieving the objectives of the lesson. Rubric Objective Full Credit Partial Credit No Credit IN GENERAL Mastery Partial Mastery Little or No Mastery Ask a valid testable question about worm behavior Make a valid hypothesis about the effects of one variable on worm behavior Student came up with a valid testable question related to worm behavior. Student s hypothesis was reasonable based on the question and on prior knowledge. Student s question was not a valid testable question or was not directly related to worm behavior. Student s hypothesis was related to the question, but not entirely reasonable. Student s question was not testable and was in no way related to worm behavior OR student made no attempt. Hypothesis had no bearing on the question and/or was wholly unreasonable given background knowledge OR student made no attempt. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 6 of 10

7 Test a single variable (light, temperature, or amount of water) while keeping all other conditions constant Student kept all conditions constant (as much as reasonably possible) while testing a single variable. Student tested a single variable, but did not always remember to keep other conditions constant. Student consistently varied more than one condition and did not show an understanding of the importance of controlled variables. Objective Full Credit Partial Credit No Credit Make an appropriate and accurate graph of the independent variable (the variable being tested) versus the dependent variable (worm behavior) Student graphed data accurately. Student attempted to graph data, but made some mistakes. Explain how at least one variable affects worm behavior Relate the results of the investigation to the Happy Worms Company scenario and propose a series of suggestions to the Happy Worms Company Student provided an explanation of the effect of the tested variable on worm behavior; explanation is reasonable given prior knowledge and the observations made. Student showed an understanding that the investigation modeled the problem in some way and proposed several suggestions that are reasonable given the results of the investigation. Student provided an explanation of the effect of the tested variable on worm behavior, but the explanation is not consistent with prior knowledge or the data collected. Student tried to relate the results of the investigation to the problem, but did not show a complete understanding. Student proposed a suggestion, but one that is inconsistent with the results of the investigation. Student made no attempt to graph data properly. Student made no attempt to provide a reasonable explanation. Student did not attempt to relate the investigation to the problem or to propose a reasonable solution. Identify problems with the investigation and propose modifications to improve the investigation (If applicable) Student described at least one problem with the investigation and proposed a reasonable solution. Student described at least one problem with the investigation but did not propose a reasonable solution. Student made no attempt to analyze the investigation design. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 7 of 10

8 Options and Suggestions for Differentiation Quick Lab: Have the whole class experiment with a single variable, determining beforehand the values of the controlled variables. For example, compare the behavior of worms when they are given a choice between moist and dry paper towels. Use five worms for one trial; allow 5 minutes for the trial. Students can do this in groups and compare their results. Extended Option: Run the investigation with a lot of worms in a terrarium over a few days or weeks to see if the results differ over time. Open Inquiry: Allow students to choose their own variables through class discussion. Other variables students might bring up include color choice, food choice (fresh versus dry leaves), or dirt versus sand. Happy Worms Company Student Planning Sheet Topic of lab (what the lab is about) best conditions for growing worms Variables (things I can change) temperature, light, surface, moistness Testable question Do worms prefer warm or cold areas? Variable I will test (variable I will change to see what happens) I will change the temperature. Variables I will not test (variables I will keep the same throughout the investigation) I will keep the amount of light and amount of water the same. This is a fair test because I am changing just one variable. I am changing temperature, but I am keeping the amount of light and the amount of water the same. Hypothesis (what I think will happen and why I think so) I think that worms will prefer warm areas because warm is more comfortable to me than cold. Make a sketch of your setup. Make sure to label each part. Procedures (list of the steps I will take to try to answer the question) 1. Place a sandwich bag half full of cool water on one side and a sandwich bag half full of warm water on the other side. 2. Place a moist paper towel across both bags. 3. Place five worms in the center of the paper towel, trying to place half of each worm on each bag (half warm, half cold). 4. Cover the worms and both bags of water with a shoebox. 5. Wait for five minutes. 6. Lift the box and record how many worms are on the warm side and how many are on the cold side. 7. Return the worms to the teacher, get 5 new worms, and repeat the experiment with a new moist paper towel. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 8 of 10

9 8. Repeat the experiment one last time (for a total of 3, with 15 worms used). 9. Record results on a graph. Student Record Sheet Circle the variable that you are testing. Trial Amount of Light Temperature Moisture Observations # 1 All worms were kept in the dark. Warm and cold The paper towel was moist on both sides. 4 worms were on the cold side, and 1 worm was on the warm side. The worm on the warm side seemed to be turning in circles. Student Analysis Sheet Variable Temperature (write your variable here) Use the graph below to plot your data. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 9 of 10

10 Did the worms prefer one condition over another? Yes. The worms preferred the cooler area. What is one thing you would want to make sure you did to keep your worms comfortable? I would make the temperature of the area that I keep the worms cool. Discovery Education Science Hands-On Lab Discovery Communications, LLC Page 10 of 10