LaBarbera-Biology of B-movie monsters0

LaBarbera-Biology of B-movie monsters0 - The Biology of...

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1 The Biology of B-Movie Monsters BY Michael C. LaBarbera SESSION 1 : Biology and Geometry Collide! Size has been one of the most popular themes in monster movies, especially those from my favorite era, the 1950s. The premise is invariably to take something out of its usual context--make people small or something else (gorillas, grasshoppers, amoebae, etc.) large--and then play with the consequences. However, Hollywood's approach to the concept has been, from a biologist's perspective, hopelessly naïve. Absolute size cannot be treated in isolation; size per se affects almost every aspect of an organism's biology. Indeed, the effects of size on biology are sufficiently pervasive and the study of these effects sufficiently rich in biological insight that the field has earned a name of its own: "scaling." The conceptual foundations of scaling relationships lie in geometry. Take any object--a sphere, a cube, a humanoid shape. Such an object will have a number of geometric properties of which length, area, and volume are of the most immediate relevance. All areas (surface area, cross- sectional area, etc.) will be proportional to some measure of length squared (i.e., length times length); volumes will be proportional to length cubed (length times length times length). Equivalently, lengths are proportional to the square root of an area or the cube root of a volume. If you change the size of this object but keep its shape (i.e., relative linear proportions) constant, something curious happens. Let's say that you increase the length by a factor of two. Areas are proportional to length squared, but the new length is twice the old, so the new area is proportional to the square of twice the old length: i.e., the new area is not twice the old area, but four times the old area (2L x 2L). Similarly, volumes are proportional to length cubed, so the new volume is not twice the old, but two cubed or eight times the old volume (2L x 2L x 2L). As "size" changes, volumes change faster than areas, and areas change faster than linear dimensions. The biological significance of these geometric facts lies in the observations that related aspects of an organism's biology often depend on different geometric aspects. Take physical forces. In the cube on the left, length = 1 and volume = 1 (L x L x L). The cube in the middle, where L=2, has a volume of 8. And in the cube on the right, L=3 and V=27. In each example, linear dimensions double, but area increases by four times.
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2 The magnitude of surface tension forces is proportional to the wetted perimeter (a length); a water strider needs long feet, not big feet, to skate on the surface of a pond. Adhesive forces are proportional to contact areas; geckos need broad, flat feet covered with millions of tiny setae to walk on the ceiling.
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This note was uploaded on 08/28/2011 for the course ESE 585 taught by Professor Richardhoward during the Fall '11 term at Purdue University-West Lafayette.

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LaBarbera-Biology of B-movie monsters0 - The Biology of...

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