Lewis/Life - Teaching Techniques

Chapter 34 - Teaching Techniques

A. General Tips
** See the General Tips notes in Chapter 30 of this Instructor's Manual.
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
Bring in props. This is an especially valuable idea if your course does not include a laboratory component. If you have a skeleton (human or otherwise), bring it in. Bring in some limbs with delinated muscles too. Show the students how the bones and muscles interact.
Don't neglect the invertebrates. Bring in any examples you may have of exoskeletons. If you don't have any readily available, ask the students about eating crab legs. How does the muscle attach? What are those stiff pieces of tissue extending from the tissue down into the crab meat? What about shrimp? Lobster?
Encourage your students to examine the muscles of a chicken. A chicken leg and thigh offers easily separable muscles, particularly if the meat has been well cooked. Students can also see how the muscles attach to the bone. Students often do not realize how tough and how complete the muscle-bone attachment is.
If you have a beef round bone (available from any grocery or meat store), you can demonstrate the differences between compact and spongy bone. You can also show the marrow.
Do the "Feel your head" experiment described in the Additional Topics for Discussion section of this book. Relate this to Biology in Action 34.1.
** To demonstrate the collagen and mineral components of bone, try this. Take a chicken bone and bake it for several hours in a fairly hot (>400° F) oven. The bone will be brittle. When you take the bone to class, you will be able to flake it with a probe because the protein has been destroyed.
Take another chicken bone and soak it overnight in any reasonably strong nitric acid solution. Vinegar or acetic acid may be substituted. The bone will be rubbery because the mineral content is no longer present.
C. Hints Related to Specific Chapter Topics
- I.A. Stress the commonality. Lewis states that skeletons are all composed of the same types of cells and have similar spatial patterns. This is an important point.
- III.A. You can demonstrate the hydrostatic skeleton by using a sausage-type water-filled balloon. You may need a student to help you hold one end of your hydrostatic animal. You can use double sided tape to show creeping movement. You can also use tape to show both longitudinal and circular muscles. Try the movements shown in Figure 34.2.
- III.B. Some interesting points about exoskeletons: Literally the arthropods outgrow their skeletons. When an arthropod sheds its old skeleton, the new skeleton is soft and moist. For an extra assignment challenge the students to find out why the new exoskeleton solidifies. Ask too if there is a difference in the ways the exoskeletons of water animals and land animals harden.
  You can tell the age of many clams by counting their rings, just like a tree. Ask the students why or how this happens.
- III.C. The cartilaginous nature of the shark is mentioned. Evolutionary, the earliest sharks had osseous skeletons. The cartilage skeleton is actually a degeneration.
- V. In dealing with the cells and tissues of the vertebrate skeleton, you might want to note that some of our students will have learned that the tendons and ligaments are separate skeletal components. That is certainly a valid way of delineating the skeleton. This is an overview of vertebrate biology and such a distinction may be beyond the course objectives.
- V.B. If you don't do the chicken bone experiment mentioned above, at least discuss it. Ask the students why the baking destroys the protein and why the minerals "disappear" in the nitric acid.
- VI.A. The opening line of this section asks students to recall the three types of muscle cells. Some of them might recall from Chapter 30 that the myoepithelial cells were also mentioned. These are not true muscle cells, even though they are contractile.
  To play devil's advocate with this section, ask the students if they know of any striated muscles that are not under voluntary control. (One answer is the diaphragm.) Also, we do have some control over some of our smooth (involuntary) muscles. This is especially true for people who are good at biofeedback techniques. The important thing is that voluntary and involuntary are not absolutes.
- VI.B. Figure 34.14 shows amoeboid movement. Science is just beginning to understand how this works. But notice the universality of the actin/myosin complex.
- VI.C. The discussion on insect flight is a fascinating one. If you cannot readily find a picture to show your class, refer to your general zoology book. Most of these have diagrams illustrating the contraction of the two sets of insect flight muscles.
- VI.D.2. Lewis suggests in Figure 34.21 that the individual can simulate the sliding filament model with the fingers. This is a good demonstration. Another good demonstration can be done with two test tubes and a two-headed test tube brush. The bristles are the myosin paddles that form the cross bridges with the sides of the test tubes.
- VI.D.4. Note the use of the term tetanus. This term should not be confused with the disease tetanus mentioned in Chapter 31 of this Instructor's Manual.