I love spaghetti. If I have a choice of what to eat, I will invariably choose pasta in some form.
It hit me that the process of cooking pasta can be a good analogy for the process of evolution.
Imagine you are cooking a pot full of pasta in various forms: penne, elbows, bowties, and angel hair. OK, 10 minutes or so in boiling water, and it's ready.
The next step is to drain the water from the pasta. You set your colander up in the sink, and dump the potful of water and pasta into it (watch out, because the water is scalding!). The colander separates the water from the pasta.
The process of filtering the water from the pasta is the crucial step--think of the various shapes of pasta as a species of animal, and the different shapes represent genetic mutations to that species that have happened through natural processes. The water represents the environment in which the species lives. The colander represents natural selection. Separating the water out via the colander's holes represents a change to the species' environment. The process of natural selection is the "filter", where organisms that can adapt to the change angel hair) are allowed through the filter of natural selection (the colander holes), and all others (penne, elbows, and bowties) are selected for extinction because they didn't fit through the colander holes. The angel hair represents the individuals that could adapt to the change in their environment.
I have to think this through a bit more, but after dinner!