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|  | Excerpts from AP Biology Teachers Discussion Group
Tip: "This past school year, when we did the fetal pigs at the end of the year, it took my classes two days (90-minute periods each day) to complete the dissection. These were not AP, Pre-AP™, or honors-level biology students. I told them that if the pigs were mutilated, or if they didn't follow directions, they would take a zero on the lab and that the lab would count double since it was a two-day project. They followed the lab protocol to the letter and looked at every organ system. No pigs were mutilated and, I believe, the students learned a lot about the anatomy of a mammal.
The point that I wanted to make is that, given a good protocol and a lot of supervision and direction, dissection is still a legitimate learning tool. The fetal pig is the only dissection that we do in a year. I stopped most dissections years ago because I got tired of introducing the dissection and having a student say, 'Oh, I did that in seventh grade.' I didn't see the point in repeating it if most of the students had done it in seventh grade. The fetal pig is the only dissection that the seventh grade teachers haven't appropriated from us. Also, when the grass frog became a threatened species because of high school dissections, I couldn't justify the frog dissection after teaching an ecology unit. When my students object to the fetal pig dissection, I tell them that 'mama pig' became bacon. It may not be literally true, but as long as pigs are raised for food they will not become endangered."
-- Jo Ann Burman, Andress High School, El Paso, Texas. 8/17/99
Question: "What is an accurate way to determine the age of a fetal pig?"
Answer 1: "I have used a chart that is virtually the same as those presented (in many books). A number of the pigs we use are postnatal according to the chart. When my students questioned whether or not they were truly fetuses, we noted the presence of the umbilicus (as well as other internal evidence such as the ductus arteriosis). Still, it makes me question the basis of the chart. Perhaps different breeds, such as Chester White, Duroc, Hampshire, etc., have different prenatal and postnatal growth rates and ranges. I have stopped using the chart, but I can't help wondering why the chart remains in the literature, such as the manual sold by Carolina."
-- Bob Goodman, Hunter College High School, New York, New York. 5/21/01
Answer 2: "There is a 'formula' used in some of the commercial fetal pig dissection manuals that goes like this: L (length in cm) = (10*0.016A)/2 where A =age of fetus in days. Students measure pigs, then solve for A (they have to use a logarithm); results are ± 10% from what I gather. Good use of math in a very descriptive lab."
-- Todd Bennethum, Thunder Ridge High School, Highlands Ranch, Colorado. 5/21/01
Tip: "Try rats. They're less expensive than fetal pigs, they seem to be readily available, and there are plenty of lab materials available."
-- Alexa Noble, Oak Ridge High School, Conroe, Texas. 8/22/99
Question: "Please tell me from what sources you obtained the information that grass frogs became endangered due to high school dissection."
Answer 1: "It's not just the leopard frogs that are in decline. A large number of amphibians are declining today all over the earth. I would venture to say that none of this is due to frog dissections. Matter of fact, there is a group of herpetologists that are trying to find out where the problem originates. Many suggestions are habitat loss, increased UV light, pollution, and over collecting. It seems that there may be multiple reasons depending on the species.
In New Mexico and Arizona, one of the main reasons for leopard frog decline is the introduction and spread of the bullfrog. Bullfrogs in the West do not have any natural enemies as they do in the East where they are native, so consequently they multiply uncontrollably.
Dissecting bullfrogs collected from the West could help, but I doubt it. We as science teachers need to be better informed about the animals that we work with. There are at least nine species of leopard frogs in the U.S. Only four are considered to be endangered, all in the West. If we do dissect leopards frogs, we should be sure of their origin. By the way, most are coming from Mexico from irrigation canals in agricultural areas. (Check out some Web sites in "See also.") None of them state that dissection is the reason for the decline."
-- Terry Hibbitts, Wylie High School, Wylie, Texas. 8/21/99
Answer 2: "Could it be that what we are witnessing in the amphibian populations as a whole is merely a natural extinction event? After all, nature selects against those that cannot maintain homeostasis for whatever reason (and as much as we would like to try to, we cannot remove man from nature). True, as a species, we have done more to increase the extinction of many organisms in our stay here on the planet, but extinctions will continue long after we are gone. Trying to pinpoint blame for any extinction event on any one cause, except for maybe an asteroid the size of Dallas/Ft. Worth, is probably misguided energy."
-- Frank R. Simpson, Jr., Miles High School, Miles, Texas. 8/23/99
Answer 3: "I, too, disagree that the frog population is suffering due to classroom dissection. Much concern had recently been placed on the discovery of malformed frogs (additional legs, missing limbs). I had heard that the suspected culprit is the infestation of a nematode that somehow affects the development of the frog from its tadpole stage. (I heard this quite some time ago, so the information may have changed.) Since these malformed frogs would be at a disadvantage, they would more than likely be 'naturally selected' out. Thus, the population overall would decrease. This does not diminish the importance of amphibians in the environment as bio-indicators, but may offer another twist to their remarked disappearance."
-- Marianne Lapp, Burlington City High School, Burlington, New Jersey. 8/28/99
Tip: "In later years, when doing dissections, I have had at least two classes share the same specimen. This forces students to do a good job on their own specimen, and allows us time to go into more detail and look for blood vessels and other structures. Several of you have written about the high cost of pigs, and I believe this will help. With disposal being a problem in many places, this reduces the cost of purchase of specimens as well as disposal. This has worked very well for me."
-- Theresa Knapp Holtzclaw, Clinton, Tennessee. 8/24/99
Question: "I realize many of you are being held 'hostage' by the fetal pig market as am I. Is there anyone out there who knows of a reasonable vendor for fetal pigs these days? What, if anything, are you all doing for alternatives to fetal pigs if price is a factor?"
Answer: "The ones we found last year were terrible... mushy and khaki/green color and poorly preserved. We had stepped down to save money. We have decided to switch to cats and just put more students per animal -- instead of two to a pig we are going to have four to a cat, I hope."
-- Charlotte Freeman, Girls Preparatory School, Chattanooga, Tennessee. 8/20/99
Question: "How about mollusks for dissection?"
Answer 1: "I have dissected clams with my classes also, but ultimately found it unsatisfactory and have given it up. It's best to use fresh (not frozen) clams. Although I have occasionally identified internal organs (if the clams are very fresh), I haven't been able to describe them so that students can find them with regularity.
I have my students do a project at the end of the year. There are always a few desperate students who never quite believe I was serious about the assignment. I reserve items such as this for them. They dissect and prepare a video with narrative and worksheets. After 12 years in school, they are very good at it, too! I haven't asked for clams, though. Maybe this year."
-- Lesli Adler, TS Wootton High School, Rockville, Maryland. 11/28/99
Answer 2: "Clams are easy to get around here and reasonably priced, but my experience has been that the internal anatomy is very difficult to recognize. The adductor muscles, mantle, and gills were easy to identify, but cut that visceral mass a mm too deep or too superficial and the student can miss everything. Even a good cut can't compensate for the lack of contrast between the structures."
-- Jane Davis, Red Bank Catholic High School Red Bank, New Jersey. 11/28/99
Answer 3: "I am a marine biologist and happen to have a lot of experience with mollusks, mostly oysters and mussels. I have dissected more than my share of clams. I agree that with high school students, the best mollusk to dissect is a squid. I also buy whole frozen ones and can usually get them fresh around here at a seafood store in the early spring. Squid are easy to dissect and I think the students can learn a lot from them. As far as dissecting clams, it is a lot better to use fresh clams. The preserved ones smell really bad and it turns kids off. The preserved ones are pegged to make opening them easier, but you really need to bring in some screwdrivers and hammers. You have to be very careful with the kids, it is easy for them to get cut trying to open a clam. Just due to experience, I am pretty good at opening them, so I open them before the lab, and then give a demo at the start of the lab, showing students how I opened them.
I did a rather long research project on oyster nutrition and had to study gut contents. It took me a long time to recognize parts. I have only done this dissection with high school students a few times and stopped doing it because I questioned the value of spending time on this. I basically had to spend one-on-one time with each lab group to help the kids find the parts, since there is only one of me; groups would go ahead and just mash up the tissue, then it would take me too long to help them identify parts from the mess.
If you are set on trying this dissection, check in older high school and college lab manuals to find dissection directions and diagrams and make sure the students can determine anterior, posterior, dorsal, and ventral so that they can orient themselves before they start cutting."
-- Sande Ivey, Bangor Area Senior High School, Bangor, Pennsylvania. 11/28/99
Answer 4: "If you want an interesting mollusk to dissect, try the squid. You can go to the frozen fish section in your supermarket and pick up a box of 20 or so for about eight dollars. If you use them right after they thaw, and dedicate new scalpels and scissors to the dissection, you can persuade the Home Economics department to swap rooms for a day and end up making calamari out of the mantle. We do this with great gusto every year. I found great materials on dissection of squid if anyone is interested, plus you can accompany this with a discussion on Archeteuthis (spelling anyone?), the giant squid."
-- Eloise Farmer, Torrington High School, Torrington, Connecticut. 11/27/99
Question: "Has anyone ever done a clam dissection before? I tried to get some variety in our dissections this year, but the book I'm using (How to Dissect) is SO unclear for this section. I was hoping that someone could tell me what I could realistically look for and what would pose problems for the dissection (i.e., is opening up the valves complicated?). Any hints, tips, and/or Web sites would be greatly appreciated."
Answer: "I have done clam dissections in the past with my pre-AP kids. Often times I found the preserved clams difficult to dissect, and it is hard to locate the heart. My suggestion would be to go to your local grocer and buy some fresh clams. Place them in a dish with some salt water and gently begin adding Epsom salt to their water. This will anaesthetize them and then gently slide a scalpel under one valve and remove it. Remove the mantle, and you should be able to see the heart beating. I always had good luck with this one."
-- Franklin M. Bell, St. Mary's Hall, San Antonio, Texas. 12/8/99
Question: "How about squid dissections?"
Answer: "They are a fascinating mollusk to dissect and they are fairly cheap and easy to get from a fish store (at least here in New York City where they are considered a delicacy by several cultures).
I wrote up a dissection lab of squid with Robert Costello (who is now at the Smithsonian). He and I originally designed the lab for our seventh grade ecology classes, but I think older students could expand on the lab, especially if they get into the eyes and brain, which we hardly touch. We developed a fairly cool technique for highlighting the organs that may be applicable for the clam as well (though we haven't tried it). What we do is simply inject the organs with diluted food coloring. We found that if you remove the beak it is possible to use a Pasteur pipette to inject into the digestive system. You could also do it from the anal end with a syringe. This is much trickier and takes some practice to find the anus near the ink sac. We also found that with a bit of practice you can inject the gill hearts and systemic heart and adjoining blood vessels.
Honestly, we help the kids and out of a class with 12 groups we usually get three or four that come out super. We then have the rest of the class look on. I would think that with some practice one might be able to do a similar thing with clams. Though I just highlighted some of the unique things we do, we also have the kids examine the external anatomy, overall body organization, method of locomotion, and so on."
-- Bob Goodman, Hunter College High School, New York. 11/28/99
Question: "What about using minks?"
Answer 1: "We once looked into dissecting minks also and decided against it. They are very greasy, making the dissection difficult (if I remember correctly!). We opted for the large fetal pigs, with the dyed veins and arteries, despite the price difference. I would probably go with rats over minks, due to the ease of dissection, but fetal pigs really are the best for anatomical studies."
-- Bonnie Polan, Beverly High School, Beverly, Massachusetts. 1/4/00
Answer 2: "One of my students did a mink last year as part of an independent study (mammalian biomechanics). First off, it arrived without paws, probably to aid the skinning process, for which these poor creatures are raised. Secondly, it stunk. The mink contains a scent gland that really smells if you pop it. Thirdly, there seems to be no good mink dissection manual, so you're on your own. I'd go for rats, if pigs are not an option."
-- Jonathan Calos, Emma Willard School. Troy, New York. 1/5/00
Question: "How do you handle students who do not want to participate in dissection?"
Answer: "I am not sure of the legal aspects, but having taught AP Biology for 15 years, I have certainly come across those students who prefer not to dissect. Since my students always work in teams during laboratory activities, I allow them to work with the team as the reader (of the dissecting manual giving instructions and the list of parts to be identified) for the team. They are still responsible for EVERYTHING that the other members of the team are held accountable for, but do not participate 'hands on.' They take all oral and written quizzes over anatomical and physiological aspects, as well as the lab practicals.
This has always been acceptable to my students who initially object to the dissection procedure itself and, most of the time, they end up wanting to participate in the dissection! I have an ex-student in veterinarian school right now who, the first three days as a reader, was teary eyed through the whole thing!"
-- Linda James, Midway High School, Hewitt, Texas. 3/22/00
Question: "Any tips for cat dissection?"
Answer: "I purchased a cat dissection video from WARDS (I think -- I am not at school at the moment). It is pretty good -- goes through each body system, and you can start and stop it. I also have been making my own video using my flexcam. The students say mine is better, but of course, we all agree that it is not a terrific substitute."
-- Patti Carothers, Monte Vista High School, Danville, California. 3/28/00
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