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.