Saturday, January 24, 2009

Prac book drawings

I spent a lot of last year drawing bones, mostly skulls, with a foray into forelimbs. Here are some of the highlights. I had to memorise the names and locations of all these bones for my exam. I managed it okay, but the day after the exam, I couldn't remember them any more. Luckily I have my sketchbook to reminisce over. I think you can make these pictures bigger by clicking on them.

In the picture below, 'TS' stands for transverse section, which is a paper-thin slice of an animal that has been preserved on a microscope slide. Preparing the specimen like this shows where all the bones, organs and muscles are located in that part of the body. I think I've labelled the vertebrae wrongly, but you get the idea. The little spots on either side of the specimen are feathers. As well as the chicken embryo, I've had to draw transverse sections of a baby turtle, a rat embryo and a tadpole. It was like a petting zoo, only all the baby animals were inside out.

Tuesday, January 20, 2009

Fish out of water

My mother is a fish.

-William Faulkner, As I Lay Dying.

A staple illustration of biology texts is the diagram of vertebrate forelimbs. The bones, for all their different shapes and sizes, are the same bones. The same basic structures have been used to make legs, flippers and wings.
The beginnings of these later-evolved bones can be found in the fins of the modern-day lungfish and the coelocanth (both pictured below), which are believed to be living fossils from the time fish began to take to land. The structures that became our arms and legs were originally made for moving through water. Our bodies have been bequeathed to us by fish.

But it’s not only our arms and legs they have left us. The earliest fish were jawless animals who sucked, tore and filtered their prey from the water. One theory says that the lower jaw evolved from a bone that was originally an arch to support the gills. The structure that, in human beings, allowed the development of speech, with all the implications of that revolution, might have started out as a bony strut that helped fish to breathe oxygen from water. Maybe the only response to a revelation like this is to let your mouth hang open, and gape wordlessly like a stunned mullet.