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T R I E D A N D true Bean plants: A growth experience Teaching plant growth to seventh-grade life science students has been interesting for me because I grew up in a rural area and always had to help in the garden. I made many assumptions about what my rural and suburban students knew. One year I decided to have them grow plants to observe the roots, stems, leaves, flowers, and fruit as we studied these parts. To keep it simple, I bought nine-bean soup mix from the grocery store and allowed the students to choose anything from the mix except the split peas. This way they had a variety of seeds to choose from and it was inexpensive for me. One bag provides more than enough seeds for each of my 125 students to chose four beans. Materials for this lab include a bag of topsoil or potting soil; a bag of small stones or gravel; 125 clear, colorless, plastic cups; plastic wrap; and rubber bands. Students are given the following directions verbally or on paper: 1. Put one layer of stones in the bottom of your cup. 2. Add soil, leaving 1 cm of space at the top. 3. Pick four beans—either four of the same type or four different types. 4. Place the beans halfway down the side of the cup at the 3, 6, 9, and 12 o’clock positions, making sure they are visible (see Figure 1). 5. On the outside of the cup, number each FIGURE 1 Setup bean 1 through 4 with a grease pencil or permanent marker. Write your name on the bottom of the cup. 6. Find the mass of the total system before you add water. Record this in your data table. 7. Decide how much water to add using a graduated cylinder. 44 science scope April 2004 Base this on any past experiences with houseplants and what you observe as you add the water. Does it still look dry? If so, add more, keeping track of the total amount added. Record this in your data table. Slowly pour the water into the cup. Data table A Date Bean plant observations Mass Location Observations Mass before of water adding (1 mL = 1 g) water 8. Seal the cup with plastic wrap and a rubber band to keep the system from drying out until the seeds have germinated. 9. Decide where you will store your system out of the way of other classes. Record the location in your data table. (I allow them to put their cups anywhere, such as in the cupboards, on the windowsill, in a drawer, or on the top of the cupboards. Students are not told how to do several parts because they learn much more from trying different things [inquiry], observing what their classmates are doing, and drawing conclusions. This is not a controlled experiment in the “only one variable” sense. I’m amazed at where they put them!) At the end of the first day, after the bean plantings have been set up and stored, we discuss • why the rocks needed to be in first (drainage), • why water wasn’t added before massing (this information will be useful at the end), Donna West is a science teacher at Bay Trail Middle School in Penfield, New York. T R I E D A N D true FIGURE 2 Bean research and lab analysis You have 30 minutes to complete this assignment. 1. On your own paper, in your neatest handwriting, and using all you have learned and observed about plants, summarize each bean plant structure. Devote one paragraph to each structure and one paragraph for a conclusion. Also include an introduction that explains what you did to set up this experiment and conclusion. Include anything else that you observed as well. a. Seeds: • Monocot or dicot? How do you know? • How long did germination take? If a seed didn’t germinate, what are some possible reasons why it didn’t? • Does the direction the seed is planted (right side up or upside down) affect the direction the roots and stems grow? How do you know? • Where did the cotyledons go? What are they for? • What appeared first—root, stem, or leaves? How do you know? b. Roots: • What kind were they—tap or fibrous? How do you know? • What direction did they grow? • What affects the direction the roots grow? c. Stems: • What kind were they? Herbaceous or woody? • How tall did they grow compared to other bean plants you observe in the room? Why? • If a stem broke, what happened? d. Leaves: • How many per plant? • How big was your biggest leaf? Compared to other bean plants in the room, were yours smaller, the same, or larger? Why? • What kind—broad or needle-like? • why we covered the cups with plastic wrap (keep moisture in for germination), • how much water they added and why they chose that amount (so they can share their reasoning with the class), • why they chose the locations they did to store their plants (so they can hear what others are thinking and rethink their misconceptions), and • what types of observations would be appropriate for the data table (for example, bean #4 germinated and roots are visible, bean #2 looks moldy, or the soil has settled). • Parallel or net veins in the leaves? • Color—dark green or lighter than most? Why? • How did they feel—smooth, fuzzy, sticky, powdery? e. Flowers: • How many days from germination until flowers formed? • Location of flowers—top of stem or near leaves? • How many flowers per plant? • Numbers of pistils, stamen, petals, and sepals? • Color? f. Fruit: • What will the fruit of this plant be? • Where will the fruit be located? 2. Conduct an analysis of your numerical data. Use sentences that restate the question to make your answers clear. a. Calculate the amount of mass your whole system (cup, soil, plants, and stones) gained or lost. (Assume that the soil is completely dry and the mass of the soil remains constant.) To do this, subtract the mass today from the mass on the first day. If the answer is a positive number, your system gained. If the mass is a negative number, your system lost. Explain the gain or loss. b. What is the total amount of water you added to your system? How does this compare to any weight gain of your system? Where is that mass now? c. What else, besides the water, did the plant take in? d. Where did all the root, stem, and leaf tissue come from? 3. Graphing the height of the bean plants. a. Create a line graph of the change in the heights of your four plants using four separate, different-colored lines. Be sure to title your graph, label the x and y axes, and make a key. When students arrive the next day, they remass the cup and its contents before adding water, then add more water, discard the plastic wrap if they see signs of germination, and return the plant to its storage spot or choose a new storage location. Students discuss things such as “My plant is yellow (after being kept in the cupboard) because I must have planted yellow beans,” or “My plants are tall (after being kept in the cupboard) because they grow best in the dark,” or “My plants are short (after being kept on the windowsill) because they are getting too much Sun.” April 2004 science scope 45 T R I E D A N D true FIGURE 3 Rubric Needs improvement Topic and possible points Excellent Experiment (5) data tables complete and neat, data tables mostly complete show good observation skills data tables and observations need more thorough work Part 1 (18) complete and thorough, shows learning occurred each question was answered, but could be more thorough or correct most answers are incorrect, short, vague, or absent Part 2 (6) mass difference calculated, labeled, and explained thoroughly mass difference calculated, explanation could be more thorough mass not calculated or explanation missing Writing mechanics (5) spelling, capitalization, and word selection are good spelling, capitalization, and word selection have errors many spelling, capitalization, and word choice errors Numbers (3) assigned to lines, not spaces between assigned to lines, not spaces between; starting numbers incorrect assigned to spaces or missing Dates (2) consecutive and continuous not consecutive or not continuous not consecutive and not continuous Labels (2) both bottom and side labels are present and accurate one label accurate missing one or both, or both inaccurate Key to lines (1) present present but inaccurate no key Sensible (1) graph shows growth that is accurate graph shows questionable plant growth graph shows inaccurate plant growth Neatness (2) neat mostly neat messy, illegible in parts Satisfactory Data analysis Graph In their journals, students must list four observations about their systems and complete data table B once the plants are growing above the soil. Data table B Date Bean #1 Height of bean plants in cm Bean #2 Bean #3 Bean #4 This project should be done at a time in the curriculum that will allow students to make uninterrupted observations for a num46 science scope April 2004 ber of weeks, so don’t start it before any long vacations. I let this activity run about five weeks, which is usually long enough for the plants to develop flowers and even some beans. The time of year and latitude of your location may affect this timetable. I have been amazed to hear the reasoning students come up with to explain their observations. We address and correct misconceptions in class, which are recorded in students’ journals so I can check for comprehension. We have a five-minute discussion each time students take a daily measurement, during which they share their observations and try to explain what they have observed. T R I E D A N D true After the plants have gone full cycle (from seed to producing seeds), students are given a copy of the Bean Research and Lab Analysis worksheet (Figure 2) and asked to work alone to analyze what they have learned about plants based on their journal information and what we have studied in class. I also provide them with a copy of the grading rubric (Figure 3). Common misconceptions that changed are: • All seeds need sunlight to germinate. • The plant’s increase in mass comes from the plant taking in the soil. • The fruit of the plant is its beans. • Roots grow down due to the Sun. Students who held these misconcepExplore plant growth at tions prior to the activity usually www.scilinks.org. have them corrected when they hear Enter code SS040403 what others think during class discussions, learn about plant parts and growth during the plant unit, and observe firsthand how the plants change as they grow. In most cases, students have identified and corrected their misconceptions by the time they start to work on the Bean Research and Lab Analysis worksheet. The NSTA Institute… Your gateway to quality professional development The opportunities presented under the NSTA Institute are your best source for both online and face-to-face courses that meet your needs and your busy schedules… professional development tailored for science teachers and presented by NSTA and our partners: The knowledge you seek… for the grades and subjects you teach · American Museum of Natural History Seminars on Science six-week online courses incorporating Museum’s resources and interaction with their scientists and educators. CEUs and graduate credits. · The JASON Academy five-week online courses for grade 4-9 teachers in life, physical, Earth sciences and more to enhance teachers’ content background and provide teaching tools. CEU or graduate credits. NSTA member discount. · The National Teachers Enhancement Network (NTEN) delivers array of quality teaching resources and professional development opportunities to K-12 teachers. Graduate credit; tuition-free pilot courses. Take advantage of a range of academic offerings from our prestigious providers… for graduate credits or CEUs. · University of Maryland Life Sciences Program offers online courses in biology and chemistry for science teachers and a Master of Life Sciences interdisciplinary graduate degree program with concentrations in biology or chemistry. The NSTA Institute offers science professional development courses to meet your goals. All are content–rich to enhance teachers’ store of knowledge at all grade levels, and all are structured to provide new tools to help students learn more effectively. · NSTA Webwatchers combined face-to-face and online courses teach use and applications for the best of the Internet to help you harness quality resources for the science classroom through a blended program that teaches educators and administrators to search, evaluate, assemble, and share valuable online resources. Webwatchers programs are given at District or school level and location. · NSTA Convention-based Professional Development Institutes and Opportunities will be announced. Watch for information at the NSTA Institute Website. National Teachers Enhancement Network For details on these exciting professional development opportunities, visit http://institute.nsta.org CIRCLE NO. 11 ON READERS SERVICE CARD April 2004 science scope 47