It comes down to the simple fact that we are not concerned with anything we cannot see. In a traditional animal drawing course, you'd certainly break things down into their major anatomical components - skeleton, then musculature, etc. But this course is not concerned with distinguishing between animals, and, say, a tree. Or a desk. Or a car.

How we generally approach starting them differs a little but it's all focused on capturing what we see in front of us. Focusing on specific masses and structures without guessing at what's underneath.

At the end of the day, we are merely using the focus of each lesson as a new lens through which to look at the same problem - how do we break down what we see into simple pieces, how do we understand their relationships in 3D space, and how do we rebuild them on the page.

Furthermore, we're also not caught up in reproducing that reference perfectly. We observe it as closely as we can, but it's less about reproducing the image before us, but rather about using it as a source of information for each new piece we pull from it and add to our construction.

We'll make mistakes - something will be too big or too small, too short or too long, and that's fine. The focus comes down to how those forms are fitted together, how they intersect or wrap around one another, and so on. We do want to make sure we spend ample time observing our reference, carefully and frequently, and that in and of itself takes a great deal of time - but it is only towards the interest of using accurate pieces as we build up and solve the puzzle before us.