# MathBench>Population Dynamics

## The topic of the day is … equilibrium

Lots of biological processes go to an equilibrium. That means there might be a certain amount of change for a period of time, but then things stabilize. Often, the equilibrium can be described in mathematical terms. That's what we're going to do here.

Before we get to the Hardy-Weinberg Law, we need to discuss the concept of equilibrium. Equilibrium literally means “equal weights” or “equal scales”. So if you put two equally heavy objects onto an old-fashioned scale, they balance each other. Each gets pulled down equally by gravity, and the end result is that the scale, once it gets to equilibrium, will not move anymore.

Equilibrium is an important concept all over biology. Any process that goes on long enough for us to observe it is probably in some kind of equilibrium, at least in the short term. Our bodies (and those of other living things) in particular are adapted to produce equilibrium situations.

Some processes result in an equilibrium being reached very rapidly, and in other cases it takes a long time to get to equilibrium. In this module we'll discuss one process (random mating) that leads very rapidly to equilibrium. Later we'll get to another process that leads quite slowly to equilibrium.

.