|Paleo 2009 Ammonites, Nautilus (and other Molluscs)
This lab is pretty simple. You will work in teams of three. You need to do several things before the end of the lab period, but there is no formal lab report due. Instead, this lab is the introduction to the Essay you will write (more instructions for this are below under a separate heading).
There are three distinct parts to lab, which we will do together.
First ~1 hour: the zoology and ecology of the modern cephalopod Nautilus
As a team, spend about an hour researching the modern Nautilus on-line. Consider (but do not limit your questions to):
Where does it live?
What does it eat? What eats it?
Describe its basic anatomy (Print out some figures to use later).
How does its anatomy relate to the shell creation? How does Nautilus secrete its shell? (how do all molluscs secrete their shells?)
What is its shell made of?
How does it grow?
How does its anatomy and shell relate to buoyancy regulation?
What are some cool things (or mysteries) about Nautilus?
Who are their closest relatives?
Keep track of where you got your information from, it might come in handy for the essay.
Second ~1.5 hours: what are Ammonite fossils?
We have provided a number of specimens of ammonite fossils, and some modern shells of Nautilus (and some clams). The ammonites are considered to have been closely related to Nautilus. Clams are also a successful group of molluscs. Look at the shells, and then go back on-line if you need to do some more basic research.
Meet as a group with Clint when you can answer and/or show the following:
-> DETERMINE: How are ammonite fossils typically preserved? What are you actually holding when holding an Ammonite fossil?
-> DRAW for Clint: where/how does a clam secrete new shell material? Same for Nautilus. CUT a clam on the rock saw (a lab assistant with help with this). DRAW a cross-section through a clam shell and SHOW growth lines. PICK UP a shell as a prop, and show this, using your hands as the soft part of the clam and Nautilus.
SUTURE LINES: Look at the suture lines on the ammonite fossils. What do these physically represent? -> MAKE for Clint: using Play-Doh, build a model of the last (living) chamber (camera) of an ammonite, showing the phragmacone and a septa. Your model should then be directly relatable to a fossil example. YOUR MODEL must be able to show what an ammonite suture is…
THE GRAND QUESTION:
What might the complexity of ammonite sutures have resulted from? Did this complexity serve a purpose? Did natural selection drive suture patterns?
Third ~1 hour: a short laboratory experiment to garner insight into the physical process of creating complex interfaces
We will make a feature in the lab that many scientists believe resembles the form of an ammonite suture, and may indicate an underlying cause-effect to suture development. Our experiment uses a simple example of an apparatus called a Hele-Shaw cell, and consists of two glass plates separated by two-stacked thin-section cover slips (therefore, the space between the two glass plates totals roughly 300 micrometers). The upper plate has a small hole in it. We will inject glycerol, then coloured water, into this space by syringe through a tube attached to this hole. The Hele-Shaw cell is named after its inventor, Dr. H.S. Hele-Shaw who was an English scientist around the turn of the last century who worked on fluid flow for early aeroplanes and automobiles (he was an acquaintance of Charles Darwin).
What do you think causes this characteristic interface behavior? How does it work?
There is a great deal of literature on Ammonites. I have selected a couple of books, which are on closed reserve in the Gould Library (see below). You should also find several sources from the scientific literature that deal with ammonite suture complexity (there are a few recent ones that will be crucial to your essay). Use and cite critical articles in your essay, find them using Web of Science, JSTOR and GeoRef. You might also want to find a few articles that you will want to refer to in your essay either for background on ammonites, or the mechanisms and workings of natural selection, evolution and adaptation, in general.
The three books on closed-reserve in the library will help with some of the anatomical questions and the behavior of modern Nautilus: The natural history of Nautilus by P. Ward; Nautilus : the biology and paleobiology of a living fossil, by W.B. Saunders and N.H. Landman; and Ammonites by Neale Monks and Philip Palmer, 2002, Washington, D.C.: The Smithsonian Institution Press, 159 pp.
I also have Stephen Jay Gould’s Full House, which you will sign out from me and be responsible for returning to me (if you want to receive a grade for the course…)
The topic of the essay/discussion is about natural selection and the driving mechanisms of evolution, using ammonite sutures as the principal example (careful, this is neither a lab write-up, nor a book-report on ammonites!). Do complex sutures represent a direct benefit to the animal for which natural selection selected? The structure of the essay is important. It should be no more than 5 pages in length, double-spaced (length limit does not include references and any figures/diagrams you might want to use to illustrate a point or two—I recommend using diagrams where appropriate). It should be structured with an introductory paragraph where you set up the problem and its significance, a body in which you construct your arguments, and a concluding or summary paragraph. You will probably want to describe the animal a little bit in your essay (in a perfunctory way, I would guess, and perhaps as a “note” in the references (see style below) given the length limits imposed on the essay). Consider spending some time reviewing the traditional views of the function(s) and cause(s) of the suture form, and any recent scientific discussion of these views. But more importantly, build up an argument, and support it.
For the style of the essay (especially for citing references, figures in the text, “notes”, bibliographic and figure caption style) you can use the format of the journal Science, which is in the Gould Library and available through MUSE. Look up instructions for Authors on the Science homepage, to see how to use ‘Notes’ and any data that you might want to include in your essay, and pick up a recent edition of Science in the Geo Lounge area, and check it out for style and format.