Lewis/Life - Teaching Techniques

Chapter 26 - Teaching Techniques

A. General Tips
This chapter is filled with facts and terms and you may have the tendency to stress rote memorization rather than conceptualization.
I strongly recommend you utilize a comprehensive zoology book (such as Hickman and Hickman). Such a book is rich in anecdotal material that will be most appropriate for your class. Use this material, not to inundate your students with extra facts, but rather to pique their excitement about the animal world.
** Many of the points touched upon in this chapter are covered in greater detail in Unit 8.
I suggest this approach:
-- Take the time to go through this material carefully and decide which terms you will expect your students to know.
-- Note the major developmental patterns -- such as protostome/deuterostome, etc.
-- Pick themes and follow these themes. Themes could include: digestion (from the gastrovascular cavity of the cnidaria to the complex human system), nerve development (from the nerve net to the elaborate central nervous system of the vertebrata), support and protection (shells, scales, chitin, and skin, to name a few) or respiration (how do animals get their oxygen?). Keep in mind that some of these points are covered in Unit 8 so I suggest you check ahead.
-- Work from charts and diagrams. I have suggested several below.
-- Encourage anyone going into education to do extra reports -- such as on the worm diseases. They are fascinating things to know about and teachers can engage younger students quite readily in facts and figures about parasitic helminthes.
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
** You may wish to give just the briefest overview of this chapter now and hold the chapter proper until after you finish Unit 7 (Chapters 27-29), Plant Life.
** Look at Figures 26.3, 26.20, and 26.23. All three are classic charts. Know how they are related. When you begin discussing the animal phyla, I suggest you put a modified version of these three figures on the board or overhead that you keep referring back to so your students are fully aware of the relationship between the different phyla. Use these figures as your framework in this chapter and as your reference point in Unit 8.
Although this chapter lends itself well to the annotated outline, I suggest you use such a method carefully. The students who had a good "walk through the phyla" in high school would profit a great deal from an annotated outline; the students who have no concept of animal phyla would view such an assignment as straight busy work -- and they would probably be right.
A good way to start this chapter is to ask the students to write down (not to hand in) an answer to the question, "What is an animal?" Ask them to give some examples of animals, or characteristics of animals. (Most will list only mammals.) Then ask if such creatures as worms and spiders and sponges are animals.
Use anecdotes liberally with this material.
C. Hints Related to Specific Chapter Topics
- II.A. Note especially the last sentence in this section, "The measure of biological success is simply how well adapted an organism is to its environment."
- II.C. One of the biggest problems with coeloms is that students tend to equate the "body cavity" with the gut. Think of this: when discussing coeloms, hollow ≠ cavity. One analogy you might use is that of a water-filled balloon. Push your hand through the balloon so that one side touches the other side. The indentation from your hand is the digestive tract; the water-filled balloon itself is the coelom. In some animals, of course, there is very little fluid in the "balloon" and the sides of the "balloon" are almost touching. Stress Figure 26.4.
- II.D. Someone who has seen hydra may question whether or not these animals have true radial symmetry because of the way they "bud." The "bud" is not included in the symmetry concept.
  Explain that any word with some form of "cephal" has to do with the head or brain.
- III. Humans also have direct development.
  When discussing protostomes and deuterostomes, refer back to Figure 26.3. Another way to explain protostome is, "First the mouth." In other words, the mouth forms first.
  If you are going to stress the concepts of radial and spiral cleavage, stress it well because some students will not understand it. One analogy you can use to explain cleavage is a stack of ping pong balls.
- IV.A. If you are a sponge expert, you can look at the spicules and know exactly what type of sponge you have.
  Asexually sponges reproduce by budding; sexually most sponges are serial hermaphrodites. That is, they have both male and female sex cells, but not at the same time. In most sponges, sperm are released by one animal and taken into another. Fertilization and zygote development (including nourishment) take place within the parent. The ciliated larvae are released.
  If you live in a mountainous area by a swiftly moving stream and would like to find a fresh water sponge, try this: Go out into the stream and find a rock. Look on the lower part of the rock, on the side not being ravaged by the rushing water. If you see a small, brownish, jelly-like glob adhering to the rock surface, you may have found a fresh water sponge.
- IV.B. Students sometimes wonder how the nematocysts work. This is a good brief research or extra credit project. Any zoology book can help. An expert can classify a cnidarian by examining the nematocysts. Nematocysts are not "reusable." Once they are fired, they are gone. However, stem cells can and do keep reproducing the nematocysts.
  If students are really interested in reproduction in the cnidaria, you might suggest that they compare alternation of generations between plants and these animals.
- IV.C. Protonephridia are sometimes called "pre-kidneys." You might ask the class to elaborate on that idea.
- IV.D. Be certain the students understand the difference between the "real" roundworms (Nematoda) and worms that just happen to be round (Annelida). The key is that the nematodes have no segments.
  Stress Table 26.3. This table also affords plenty of opportunity for extra credit or bonus work. I especially encourage this if you have students who are going into education. A cache of grody worm stories should be a must for every elementary and secondary teacher.
- IV.E. A good introduction to this section would be to ask, "Assume the giant squid could breathe as a terrestrial animal. If everything else were the same, could the giant squid live on land?" This could lead you into a discussion of the roles of the mantle, the shell, the mucus trail or the terrestrial gastropods, the circulatory system (closed in the cephalopods, open in the gastropods), and so forth.
  Some hermaphroditic terrestrial gastropods shoot a dart into the partner's body before copulation. This dart heightens sexual excitement before the sacs of sperm are exchanged. Each partner then deposits fertilized eggs into the ground.
- IV.F. Animate the difference between deposit feeders and other types of feeders.
  Another challenge point would be to research the present day medical uses of leeches.
- IV.G. Lewis breaks the arthropoda into subphyla. Be aware that some phylogenists are trying to break this group into completely separate phyla.
  With this whole section it would be worth while to work from a chart, or to construct a chart as the discussion progresses. It is very easy for students to become lost in this material.
- IV.H. As pointed out in the text, many echinoderms like to dine on mollusks. The phrase "to clam up" literally comes from this phenomenon. If clams (which are bivalves) are able to snap their shells together quickly enough, they can literally stave off the onslaught of the sea star for up to 30 days. If they don't "clam up" fast enough or tightly enough, however, the sea star has a delightful delicacy for dinner. Although echinoderms do not exhibit cephalization, they do have a nervous system, generally consisting of three rings.
- IV.I.3. The statement is made that birds and mammals evolved from reptiles. You might ask what evidence would be necessary to make that statement.
- IV.I.4. I suggest you use a chart such as this:
  - -- Mammals
  - -- Prototheria
  - -- Egg layers
  - -- Theria
  - -- Marsupials
  - -- Placentals