Shape, Size and Geometry
What does that mean? Well, a biomechanist can have fun by creating a
hypothetical universe of all conceivable cells. This universe is
illustrated here for shape, size and geometry. So, I've plotted shape, size
and geometry to create a world of conceivable cell shapes, sizes and
geometries. By the way, geometry and shape are not the same thing. Please
bear that in mind when you're teaching basic physics or mathematics to your
students.
Cylindrical prisms, like these things here, all belong to the same class of
geometric objects. You take a circle and you translate it along an axis
and you get a circular cylinder. But, all cylinders do not have the same
shape. Some are short and broad. Others are very tall and skinny. So
shape and geometry are not the same thing. That's why you need three axes
for this hypothetical universe of cells.
Now, what happens if you increase size in this universe?
The question here is, if you start out with a small spherical cell, how
must cell shape and geometry change to accommodate two important biological
functions? The first of these functions is the interception of sunlight.
It's extraordinarily important for a photosynthetic organism. The other is
the maximization of surface area with respect to volume. Why is that
important? It's important because organisms like these unicellular plants,
use their surface area to absorb materials from their external environment
and to excrete waste materials into their environment.
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