Looking for some allometry teaching aids?

2 minute read

If you're looking for something fun for students to read about allometry, then try "The Biology of B-Movie Monsters by Michael LaBarbera. It begins with the basics of scaling laws, and moves quickly into considering problems for creatures like "The Incredible Shrinking Man:"

Because of these relatively larger surface areas, he'll be losing water at a proportionally larger rate, so he'll have to drink a lot, too. We see him drink once in the movie--he dips his hand into a puddle and sips from his cupped palm. The image is unremarkable and natural, but unfortunately wrong for his dimensions: at his size surface tension becomes a force comparable to gravity. More likely, he'd immerse his hand in the pool and withdraw it coated with a drop of water the size of his head. When he put his lips to the drop, the surface tension would force the drop down his throat whether or not he chooses to swallow.

There's a long list covering the gamut from the tensile strength of giant hydrostatic skeletons to the body proportions of infants and certain space aliens.

Or, if you're looking for something more classic, you can find J. B. S. Haldane's 1928 essay, "On Being the Right Size." It, too, covers the basics, with some interesting departures:

Similarly, the eye is a rather inefficient organ until it reaches a large size. The back of the human eye on which an image of the outside world is thrown, and which corresponds to the film of a camera, is composed of a mosaic of "rods and cones" whose diameter is little more than a length of an average light wave. Each eye has about a half a million, and for two objects to be distinguishable their images must fall on separate rods or cones. It is obvious that with fewer but larger rods and cones we should see less distinctly. If they were twice as broad two points would have to be twice as far apart before we could distinguish them at a given distance. But if their size were diminished and their number increased we should see no better. For it is impossible to form a definite image smaller than a wave-length of light. Hence a mouse's eye is not a small-scale model of a human eye.

There's some biology that we know and Haldane didn't, but it remains basically fresh -- remember that young Haldane dabbled as a science fiction writer.

And there's the added twist of Haldane's notion of allometry in social organization at the end.