Lewis/Life - Teaching Techniques

Chapter 11 - Teaching Techniques

A. General Tips
This is another chapter that students generally like. They also tend to have some gross misconceptions about this material, so it is a good chapter to begin with a non-quiz. The non-quiz will give them an opportunity to identify their own misconceptions and will give you a chance to pinpoint the direction your presentation of this material should take.
If you personally like this material, you will find that you can very easily get off on a tangent of one sort or another. Be aware of this before you begin. You will want to address the concerns of your students, but you do have a myriad of other topics still to be covered in the course.
Consider assigning extra credit or bonus point questions on the material in this chapter. One interesting bonus assignment might have to do with a historical perspective on epigenesis. What did various leaders really think?
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
If you decide to begin this material with a non-quiz, I suggest questions such as these: 1) In which cell (or cells) of the human body would you find the genes for eye color? 2) Why are identical twins always the same sex? 3) What happens when an egg is fertilized? 4) What triggers aging? 5) What is the difference between an embryo and a fetus? 6) Before birth, does the mother's blood mix with the baby's blood?
C. Hints Related to Specific Chapter Topics
Regarding Biology in Action 11.1, Kartagener syndrome should not be confused with the rare condition in which the internal organs are completely normal but their structure and position are mirror images of the norm. This latter condition is sometimes found in mirror image twins.
- I.A. Baer's generalization which became known as Baer's Law stated that features common to all members of an animal group are embryologically developed earlier than features specific to members of the group. This led to the Biogenetic Law of Müller-Haeckel, so named by Ernst Haeckel in 1868. The modern degenerate form of this law is, "Ontogeny recapitulates phylogeny."
  Incidentally, this is the same Ernst Haeckel who, in 1866, stated that the two kingdom system of Aristotle was inadequate and a three kingdom system would be more appropriate (see p. 429).
- II. Ask the students to outline the similarities and differences between the worm and the fly.
- III. Table 11.1 is a nice summary. I suggest referring to it often as you go through the stages of prenatal development. You might also wish to point out that the events are the same throughout the animal world, although the specifics of timing are unique to each species.
  Table 11.2 gives a good overview of the events of early human prenatal development. The continuum is the same throughout the animal kingdom, although there are some variations in the terminology and the specifics of the time table are not constant.
  Throughout this section you will find quite a bit of terminology. The terms connected with fertilization and gastrulation, as well as the names of the extraembryonic membranes, can cause a great deal of confusion. Have these ideas clear in your own mind and be very aware of exactly what you expect your students to know. Make mental correlations between the terminology you expect them to be familiar with now and the focus of other parts of your course.
  Table 11.3 includes information many students find fascinating. With some dogs and cats there is a slight variation in gestation time according to breed. Further information on this may be obtained from a veterinarian. Notice that the greater the length of gestation, the more approximate the gestation time becomes. Humans have a 266 day gestational period but no one would worry about a baby born at 256 days. If a dog whelps at 50 days (ten days early), the pups probably will not survive. Some experts say that elephants have about a two month window in which to give birth and that 660 days is very approximate.
- III.A.4. You can demonstrate how the nervous system was derived from the ectoderm by taking a piece of paper and forming a tube. Hold the tube up with one hand on each end of the tube and tell the class that the tube is the embryonic body. Now, with your index finger on each hand, push the tube down so you form a "tube within a tube." Tell the class that you have just demonstrated how the ectoderm folds in and over itself, forming an ectodermally derived tube inside the body proper. This tube is the neural tube. One end will convolute to form the brain. The rest will become the spinal cord.
- III.B. Figure 11.17, facts about twins, is associated with this section. If you look at this figure, you can see why it is often difficult to tell whether identical twins really are identical just by examining the amnions and chorions. To complicate matters, sometimes fraternal twins implant so close together in the uterine wall that their amnions and/or chorions actually fuse.
- V.A.3. Students are generally very interested in the progerias. You might consider making an outside assignment to research this topic.