What Do You See When You Look at a Tree? (45 min. program)

Transcription

1 What Do You See When You Look at a Tree? (45 min. program) Materials: pencils, paper (for drawing), tree identification example of bark, fruit, etc., chartboard or whiteboard to write vocabulary words, tree cookies, tree picture power point (optional), clues for tree importance activity (wood block, paper, apple, doctor s mask, water bottle, animal, umbrella, lighter, hiking boot, money, smiley face). -to obtain tree samples, contact Dr. Laurie Schimleck (lschimleck@warnell.uga.edu) Purpose: Students will challenge basic assumption and expand elementary ideas about trees. By the end of the lesson, student should be able to describe how a tree functions as a living system and explain why trees are important to humans and the environment. I. Introduction (10 minutes) What is a tree? What is a tree? (According to Webster s online dictionary, a tree is a plant with a long woody stem and few or no branches on its lower part. Biology dictionaries often say something like a woody plant at least 5 meters high with a main stem on the lower part that is usually unbranched ). Activity Tree Drawing What do you see when you look at a tree? When you hear the word tree, what comes to mind? Take a minute or two to draw the tree you pictured on the piece of paper in front of you. Choose a few students to share their pictures. Did their trees look the same? Why or why not? Are all trees in nature the same? When most of us think of trees, we imagine a large trunk, lots of branches, and tons of leaves. We don t really picture much beyond that. Stop to take a closer look, though, and you ll see that trees are so much more! Each tree is a separate living system, with many parts working together to form a whole. When this system is working properly, trees can provide all kinds of benefits to humans and the environment. Today, we ll investigate the life of trees and discover the many different things a tree can be. II. Tree Function (15 minutes) How a tree works? Are trees alive? Of course they are. They may not move as fast as other organisms, but they still need a few basic things to survive and grow: food, water, shelter/protection, air, etc. What body parts do humans use to fulfill these needs? How does a tree get the things it needs to survive? Let s build a model to help us understand how a tree works. What is a model? Scientists often build models to help them understand how things work in nature. To make things more exciting, we can build a human model to understand tree function. We ll need your help Activity Tree Factory (from Project Learning Tree, p. 269) In this activity, each of you will become a different part of the tree with a very important job. We ll work together to figure out who will be doing what. We can use a tree cookie

2 to help visualize where everything goes (refer to the cookie as the model progresses). A tree cookie is a cross-section of a tree trunk. Let s start with water. Where does a tree s water come from? Roots absorb groundwater. Trees send a large taproot down. Lateral root shoots with root hairs branch off of this. Let s get a few volunteers to be our tree roots. The taproot person should sit down with lateral roots lying around her. All roots make a sucking sound. The roots should practice this sound before moving to the next step. How does water in the roots get to the rest of the tree? Xylem, also called sapwood, carries water and nutrients up from the roots to the leaves. Heartwood, which forms the central core of the tree trunk, is made up of dense dead wood and xylem cells. Two students should stand over the taproot to represent this hardwood, bearing their muscles to symbolize strength and saying support. A few students should join hands around the heartwood and seated taproot, facing inward (and carefully avoiding the other roots), to represent xylum. The xylum says slurp. Have the roots and xylum/heartwood practice in unison to make sure they can work together. Where does the water in the xylum travel? To the leaves. Have the heartwood extend pieces of yarn to a few leaf volunteers. What do the leaves do all day? Leaves are the food factories of the tree. They use energy from the sun to convert carbon dioxide and water into oxygen and sugar in a process called photosynthesis. The leaves in our model will hold their yarn, wave their fingers, and repeat the word, food. Practice as a unit for a few seconds before moving on. How does the food in the leaves get to the rest of the tree? Phloem, also called the inner bark, carries water in sugar made in the leaves down to other parts of the tree. Have the phloem volunteers join hands and form a circle around the heartwood and xylum. They will simulate the role of phloem by reaching above their heads, grabbing for food, then squatting and releasing their hands while saying food to tree. Practice again. If appropriate, tell students than another important layer, the cambium, is a thin layer of growing tissue between the xylum and phloem. Add this layer to the model if you have time. Finally, what s missing? Bark, which protects the tree. Have a few bark volunteers cross their arms, face outward around the phloem, look tough, and say we are bark keep out! Now that the human tree model is complete, have all students act out and chant their parts simultaneously. Emphasize all the different parts that make up a tree. The trees in your neighborhood are growing just like this, all day, every day. Because trees have so many different parts that are constantly working around the clock, they provide many different services to ecosystems around the world. (An ecosystem is set of interacting living things in a physical environment all functioning as a unit.)

3 III. Why Are Trees Important? (15 minutes) Take a second to think about trees in your neighborhood. What do trees mean to you? Why are they important? Why should you and your friends care about trees? In the next minute, write down all the reasons why trees are important. After you re done, I ll put your knowledge and creativity to the test. What are some things you came up with? Let s walk around the schoolyard observing environmental cues and examining clues to see if we can discover some of the reasons why trees are important Activity Uncovering the True Value of Trees Walking around the schoolyard, help students identify goods/services that trees provide. Subtle (and occasionally overt) clues may be necessary. Bring along a bag of goodies to help students recognize trees contributions. Cover as many of the following benefits as possible (based on time and grade level): Wood (clue = wood block). Trees provide wood for a number of products. Hardwoods are especially durable and well-suited to furniture and flooring. Paper (clue = paper). The long fibers of softwoods are ideal for making strong paper products. Food (clue = apple). The leaves of trees and other plants convert sunlight into energy, which represents the primary productivity that forms the foundation of the food chain. Clean air (clue = doctor s face mask). Trees help clean the air. Show stomata on underside of leaves to illustrate this point. One acre (60m x60m of trees) produces enough oxygen for 18 people every day. Clean water (clue = water bottle). Trees help clean water by filtering contaminants and reducing erosion. Infiltration rates for forested areas are greater than for equivalent areas of turf and grass. You can present this data graphically. Observing water in the schoolyard generally illustrates this point well, too. Where does it tend to build up in relation to trees? An outdoor demonstration of water flowing down a (1) barren slope and (2) slope with vegetation including trees will also provides a nice visual. Shade (clue = umbrella). Trees provide shade that helps control temperatures and counter the adverse effects of urban heat islands. Habitat (clue = animal). Trees provide important habitat (food and shelter) for wildlife and humans. Fuels (clue = lighter). Wood and wood products are an excellent source of heat think wood fires. Biomass, especially wood, is now being used in renewable energy production throughout Georgia. Technological advances have recently made the production of liquid transportation fuels from cellulosic biomass more feasible. Place to exercise (clue = hiking boot). Trees make up forests and parklands that are popular sites for all sorts of physical activity.

4 Place to get healthy (clue = smiley face). Research shows that trees and green areas not only encourage exercise and physical activity they can reduce stress and increase attention. Next time your really want to focus go outside! Financial attraction (clue = money). Trees can provide unexpected economic benefits. People pay more to live and work near trees and green areas. People who work in or near green spaces are often more productive. In some cases, tourists travel great distances to experience the beauty of trees (cherry blossoms in Washington, DC) and the natural wonder of forests (Redwood Forests of CA). Other possibilities exist as well. Students should begin to understand trees have multiple values. You can also use this opportunity to highlight tree diversity (see supplementary activity). Not all trees are the same. Point out some differences in leaves, bark, fruit etc. Would some trees be better than others for providing shade? How about wildlife habitat or clean water? Why? Return to the classroom. See how many of the potential benefits students came up with before the outdoor exploration session. Use the bag of clues to review the importance of trees. IV. Conclusion (5 minutes) Now that we know a bit more about how trees work and why trees are important, has your opinion of trees changed? Next time you a see a tree, will you see more than a big ole trunk with a bunch of leaves? Think of all the things going on inside that tree at every hour of the day: the roots sucking up water and nutrients, the leaves making food from sunlight, the xylem and phloem carrying the food and water to other parts of the plant. Think about how each tree makes the neighborhood better for all the animals and plants that live there. Planting a tree is a fun and easy way to improve your schoolyard habitat. It s a project that will last a lifetime (in some cases, 10 lifetimes!) and help people and the environment for years to come. Take another look outside at those towering trees all around us. Think about what we ve discussed today. Again, ask yourself, what do I see when I look at a tree? The answer may surprise you! Extra Time Activities: Tree Diversity Are all trees the same? Activity Tree Diversity Go outside. First, see if students can find a tree that looks like the tree they drew. How do scientists tell trees apart? Tree scientists, called dendrologists, often use bark, leaves, fruit (often cones or seeds), flowers, or twigs (and buds) to identify trees. Conduct a quick observation/collection of the school grounds to some examples of distinct bark, leaves, fruit, or twigs that help with tree identification. Observe differences among different tree species. Help students recognize ways trees are different. (Use sample leaves, cones, seeds, and bark if clear samples are not accessible in the schoolyard). Do you think it easier or harder to identify trees in the winter? Why?

5 Bonus: Tree Extremes Tallest tree = Coastal Redwood, CA (over 370 tall) Tallest trees in GA = Eastern White Pines and Tuliptrees (around 170 tall) Largest trees (total volume) = Giant Sequoias, CA (52,508 cubic feet) Stoutest trees (diamter) = African Baobab, South Africa (almost 50 ), Montezuma Cypress, Mexico (39 ), Giant Sequoia, CA (29 ) Oldest trees = African Baobab (over 5,000 years), Bristlecone Pine (4,800 years)