Lewis/Life - Teaching Techniques

Chapter 27 - Teaching Techniques

A. General Tips
You are faced with quite a few terms directly related to plant anatomy. The vocabulary should not be the focus of your lesson. Rather, the vocabulary should be a support to a conceptual approach to this material. You should concentrate on physiological logic. In other words, ask questions like: "Why do plants have roots, stems, and leaves?" "What types of structures are necessary to transport fluids up a tree?" "Would you expect the transport vessels to be wide or narrow? Why?" Perhaps a theme for this entire unit could be conservation of water.
Instead of simply expecting the students to memorize the name and location of the Casparian strip, challenge them to know why such a strip exists in terms of the whole fluid flow set up in the plant.
** Decide in advance how much detail and how much vocabulary you will require of your students. This is especially true of the leaf anatomy.
You might wish to copy and distribute to your students the Overview of Chapter Objectives flowchart found at the beginning of this Instructor's Manual Chapter.
B. Possible Approaches to the Chapter
Cluster the work. One possible way to do this is to copy the Key Terms list from this Instructor's Manual. Ask the students to group the terms according to location or function. This can be done either very quickly in class or as an outside (no-credit) assignment.
Another possible approach is to follow a function, such as the uptake of a drop of water, from its diffusion into a root on up to its transpiration from the leaf. By doing this, you can cover most major plant parts. You can use the same approach for both primary and secondary growth.
C. Hints Related to Specific Chapter Topics
- I. Stress the common themes of all plants.
- II. I suggest using the four basic primary tissues as a key to simplicity. As you proceed through this chapter, show how everything is just an expansion of the basic "plant plan."
  Define "ground tissue." It is the background material, the bulk material, the support material. So many students will be wondering if "ground tissue" is "ground up tissue" or if it is "tissue found in the ground." Ground tissue is a serious point of misconception.
- II.A Lewis says, "Meristems may be thought of as embryonic tissue that persists throughout the life of the plant." This is an exquisite definition! Ask if meristems are composed of determinate or indeterminate cells.
- II.B. This section deals with ground tissue. You can make a chart of the different "ground tissues." Or, you can ask the students to come up with different types of charts that might be used to organize these tissues in different ways -- particularly ground tissue.
  Lewis states that parenchyma cells can help a plant survive injury or adapt to a new environment. You might challenge your students to do some research on this point.
- II.C. List the dermal adaptations. Ask about the physiological reasons for these adaptations.
  Carbon dioxide controls the amount of carbon dioxide that diffuses into the leaf. Ask why. Remind them what photosynthesis is. Some will have reverted back to their old way of thinking about photosynthesis. As an extra credit challenge, suggest your students research the size shape and distribution of stomata (or guard cells) throughout different parts of the botanical world.
  Another research point is the physiology of transpiration.
- II.D. Compare the vascular functions found in a plant with the vascular functions found in an animal. How do the sizes of the vascular tissues compare?
  Note the statement that vascular tissues form the veins in leaves. Be certain your students do not think that vascular tissues are limited to the leaves; vascular tissues are found throughout the plant.
  Note, too, the reference to water conservation. If you have made water conservation a theme for this unit, you might ask if all organisms (in this case plants) are really aquatic organisms.
- II.D.1. Tracheids come in various sizes and shape.
- II.D.2. Depending on how much detail you will be requiring, you may have to explain the difference between positive and negative pressure.
  Stress Table 27.3.
- III. As you begin this section, refer back to Table 27.1. Augment this table as necessary. Repeat the difference between angiosperms and gymnosperms. Students often need to be reminded of this several times.
- III.A. If possible, find a picture to demonstrate the rosettes mentioned here.
  Recall the definition of trichome. Ask the students why it might be logical to have trichomes as part of this epidermal covering.
- III.B. How much of this information will you require of your students? This is a good place for your students to cluster vocabulary.
- III.C. Much of the information in this section can be approached from the standpoint of basic logic. Many of the terms "do" exactly as they "sound."
- IV.A. Students usually find growth rings very interesting. They are usually surprised to learn that the reason we see rings is because the cell sizes are different. Ask them why it is logical that the spring cells are larger. Ask them also if they see why it is sometimes difficult to tell the exact age of a tree. (In a particularly dry spring, or a particularly wet summer, the cells of a ring may all be about the same size and may blend in with the ring on one side or the other.) Use Figures 27.25 and 27.26.
  Be certain the students understand where the secondary growth is occurring. Many of them have major misconceptions in this area.