The importance of anatomy.
You'll notice that anatomy is essential for drawing. It becomes difficult to accurately draw a complex pose, or even a simple one, if you don't understand what's under all that skin or fur, or even bark. Knowing how everything fits together is important.
Once you notice where that certain muscle is, shading and form become much more accurate and more natural. Knowing why the nose and eyes fall where they do make it much easier to draw from memory, and nail that natural look you were going for.
Learning the anatomy of the subject you're going to draw is quite important, and will definitely help you on several levels.
It's also easier to drawing sequences of movement. One will know what connects to what, and how they move. What is possible, and what isn't. (Range of motion)
Drawing people and other animals can be intimidating. Once you have a solid foundation, it's much easier to draw because you understand what lies underneath.
One will notice that humans and other animal's anatomy are similar. You can draw almost any other species of mammal easily if you compare it to human anatomy. Obviously, there are differences. Different body parts are adapted for different things.
Faces can be daunting. The placement of the features can be hard to place accurately.
Stock Accounts for human anatomy:
Human Anatomy Tutorials + Resources
Includes specific and general tutorials.
Animal Anatomy Tutorials and Resources: