OREGON STATE UNIVERSITY

Lesson Plans

What You Receive:

Teachers can download a notebook containing two unit plans which focus on trees and wood as a material. One unit is in biology; the other, geometry. The lessons on this site meet previous Oregon benchmarks. These lessons are in the process of being updated to Oregon's most recent benchmarks. . We encourage participating schools to use several of these lessons before they arrive to make the Wood Magic experience more complete. We also provide wood cookie name tags prior to arrival. The students can use these to study the way a tree grows by looking at the rings, and then design and craft their own name tag.

As you exit Wood Magic, you will also receive a bag full of classroom materials, including posters and additional background material. You will also be asked to complete a short survey to assess the quality of each station.

For additional information please contact Tisha Morrell at morrell@up.edu

Download Lesson Plans:

Example Lesson Plan

Lesson Eight - Why Leaves Change Colors

(see image above)

Teacher notes:

After seeing that green leaves are made up of at least two colors in the chromatography activity, students will be led into a discussion of fall coloration. This is another opportunity to discuss the nature of science. Botanists do not have all the answers to why leaves change colors, but there is much that is known! Weather patterns, as well as the chemicals present in the sap of trees, affect the colors that will be seen. Seasonal changes will be tied into the growth cycle of trees, which will then progress to how trees grow. A misconception that may need to be addressed is:

Trees grow from the bottom up. Actually trees grow from the top! This is easy to see if you think about attaching bird houses or where people have (in bad judgment) carved initials into trees or if students have seen clothesline pulleys attached to trees. All those things remain in a constant position over time. If trees grew from the bottom up, each year these items would be found higher and higher from the ground!

CIM Science Content Standard:

Life Science/Organisms: Describe the characteristics, structure, and functions of organisms; Unifying Concepts and Processes: Cause and Effect, Change, Cycle.

Goal:

Discuss fall coloration of leaves, as well as the yearly growth cycles of trees and how they grow.

Objectives:

The student will be able to:

  1. Provide an explanation for fall color changes in leaves;
  2. Explain what happens to deciduous trees throughout the year in terms of growth.

Materials:

Overheads of tree life cycles and cross section of tree stem For class demo:

  • Cup Water
  • Food coloring (green, yellow and red)
  • Optional: Balloon
  • Lesson:

    Motivation/Pre-assessment

    1. Ask students what we discovered about leaf pigments yesterday (there are more than just green in the leaves)
    2. Ask students why they think they see different colors on leaves in the fall. (Accept any reasonable explanation).

    Body

    1. Tell students that if we used a different chemical yesterday, they would have been able to separate more pigments from the leaves than just the greens and yellow. Have students give other pigments that might be present in leaves (brown, red, orange). You can tell students that there are a number of different green pigments, as well, which is why some saw different shades of green in their strips.
    2. Ask students if they remember what the purpose of the pigments are. Have a student supply the answer (They absorb sunlight to help in photosynthesis)
      5. Help students try to figure out why leaves change color in the fall. Use a cup of water and put in a few drops of yellow food coloring. What happens to the water (it turns yellow because of the yellow coloring.) Have students think of the food coloring as pigments.
    3. Ask students what would happen if you put in a lot of green coloring into the cup. (It will turn green. Some may think the two colors would blend.)
    4. Put in enough green coloring so the yellow is no longer visible and future drops of food coloring can also be masked.
    5. Ask what would happen if you put in a few drops of red? (May get various responses). Do it. (The red should not be visible if you have enough green in the cup.)
    6. See if students can equate this to leaves. Why do leaves usually appear green if they contain many pigments? (Green is present in the greatest amounts so they "overpower" the other pigments.)
    7. Ask students what would happen if you could remove the green pigment from the leaves—or from the cup. (Other colors would be visible)
    8. Equate this to the fall leaf color changes. What was needed to make the green pigment, chlorophyll? Sun What happens to the amount of sunlight as the seasons change? (less sunlight, cooler, wetter weather in the fall) Tell students that in cooler temperatures, the green pigment begins to break down. What would that do? (allow other colors to show) Eventually other pigments break down, too. The leaves no longer can absorb enough sunlight to produce pigments or carry on photosynthesis. What happens next? (the leaf dies and falls off the tree)
    9. Return to the life cycle of deciduous trees. Place the transparency on the overhead. Have students lead you through the annual cycle.
    10. Ask what happens to the tree after it loses it leaves. Does it die? (No because it is still alive in the spring!)
    11. Explain that in the winter since the temperature is cooler, the trees go dormant. Ask if someone can explain this. Equate it to hibernation. (The tree is still alive, but it is not growing.) Why? (There is less sunlight, so less energy to make food, so the tree conserves the energy it has! As spring arrives, the days get longer and warmer. The nutrients in the roots are drawn up into the tree and help make new leaves.
    12. Ask students if the same thing happens with conifers? (Show the life cycle diagram of a conifer.) (Students should know that the needles stay on all year.)
      16. Tell students that the needles drop (are shed) and are replaced year-round.) Remind students that needles are a specialized leaf. Because of the decreased sunlight available in the autumn and winter, photosynthesis declines. The results are the same as with deciduous trees. Conifers do not add new growth in the winter!
    13. Summarize (or have a student summarize) that trees grow more quickly in the spring, slow in the summer, and taper to no growth in autumn and winter.
    14. Ask students how does a tree grow? In what directions? (you are looking for up and out)
    15. Explore the change in tree height first. Ask students if the tree grows from the top up or from its roots up. (You may get students voting for both options. Don’t give them the correct choice or indicate what it is!) Ask students if they have ever seen initials carved into a tree. (yes) If they haven’t seen initials, see if they have seen other things attached to trees (pulleys, bird houses, etc.). Ask if these things have to be reset every year or if they remain at the same height. (Students should realize they remain at the same height). Ask the question again—does a tree grow from the top up or from its roots up. (From the top!)
    16. Ask students how else a tree grows besides taller. (Wider). Have students show you with their hands about how wide a sapling is. What about a mature tree? Ask how a tree grows wider? (Accept all ideas.)
    17. Show the transparency of a cross section of a tree.
    18. Ask how old the tree is? How do they know? (Some may know you can count the tree rings to age a tree.) Point out the xylem on the diagram. (It’s number 4) Ask for someone to recall the function of the xylem for the class (transports water) Point out the phloem. (It's number 2). Again, ask for its function (transports food). Ask students what they think number 1 is (bark)
    19. Help students deduce why you can count the rings of a tree to determine its age. Ask why you can count tree rings to determine the age of a tree. (Students probably won’t know.) Ask if conditions for tree growth is more favorable in the spring or summer. Remind students that trees need sun and water to grow (Spring). Ask what happens to tree growth in the spring and summer vs. fall and winter (faster when its warmer and wetter, and no growth in cooler, drier months). Tell students the xylem vessels appear narrower when it grows slowly and wider when it grows quickly. When it grows more slowly, the band is dark and when it grows more quickly, the band is light. Ask why? (Make an analogy to a balloon. When there’s no air in it, and it’s smaller, the color is dark. When you blow into it and stretch it, and it’s larger, the color is lighter. If you have a balloon, demonstrate this.) How much growth do we see in trees during cold months? (none) Help students conclude that a pattern of light and dark rings will be made each year. That’s the reason you can determine the age of a tree by counting its rings! Looking at the overhead, ask for students to point out springwood or earlywood (it's lighter in color--cells are wider) and summerwood or latewood (it's darker in color--cells are narrow). Ask where the wood from the rest of the year is found? (no growth, so no rings)
    20. You may want to point out the cambium layer on the transparency. (label 3) Tell students this is the layer were cells divide to make new cells. The xylem forms to the inside and the phloem form to the outside of the cambium. Remind students that the xylem are generally not living. The only part of the stem that’s alive is the phloem and cambium.
    21. Ask students why they shouldn’t cut initials or other marks into trees. (opens them to infection.) Ask if they can see another reason it’s not good for the tree. (You would cut into the cambium and the tree couldn’t grow there.)
      26. Tell students there are others things we can learn from looking at cross-sections of trees besides the age of a tree and we’ll be exploring that in a future lesson.

    Closure:

    Have students review what was presented in this lesson. Why do leaves change colors in the fall? (as pigments are broken down, different colors are seen) How do the seasons affect tree growth? (Trees grow more quickly during some seasons and more slowly to not at all during others) What can we tell from looking at a cross section of a tree? (How old it is) In what directions do trees grow? (from the top up and wider!)

    Extensions/Connections:

    For reading you may want the students to read The Tree by Judy Hindley or The Giving Tree by Shel Silverstein (depending on their reading levels). You can have a discussion on either/both books after the students have read them.

    For art, students can make leaf rubbings. Place a piece of paper over the vein side of a leaf. Using the side of a crayon (remove its paper wrapping), rub over the paper. You can also make fruit prints by using fruit as "rubber stamps"—cut a fruit in half crosswise, dip into paint, and press on paper. A little practice here makes perfect. Different fruits and different angles of cutting have different designs!

    Image: