What is the relationship between complexity and organization in biology?
Here's food for thought. Entropy is always considered to flow naturally in a direction of order, to disorder. That is, the higher entropy a system has, the greater degree of disorder it has, and the less amount of work it can perform.

Now, look at a cell. It is a biological system of organic molecules that are able to organise themselves in a way that outweighs the forces of entropy. To "fight" the natural tendency of the universe that moves toward a state of disorder requires a highly complex system. And, in the process of going against entropically favorable mechanisms, a cell is also able to produce its own energy (stored as potential energy, or ATP if you will).

I guess you could say, a more complex system is able to organise itself in a greater number of ways for the purpose (and I use this word very loosely, as nothing really has a purpose) of yielding entropic energy to do work.