Circulatory System
I drew this when I was taking biology in 9th grade, but it wasn't for an assignment. I started with the central mitochondrion, then added the two biggest cells. After adding the palisade, I decided to finish the cycle with some more animal cells. A random doodle.

Immunity
I drew this in 12th grade for an assignment for physiology. The assignment was to create a flowchart that demonstrates the differences between cell-mediated and antibody-mediated immunity. I've always associated phagocytes with purple, T-cells with blue and antigens with red. When I think about the different cells and tissues in the body, I connect them with colors and faces in my brain. This type of drawing helps me remember the information.
From Genome to Proteins
I drew this for an assignment in 9th grade. The assignment was to take the terms and connect them in the way shown - with little phrases describing how they interact. I took some artistic liberty with the terms because it helps me remember them.
Reproduction
I drew this in 7th grade Life Science when I was learning about the reproductive systems. The male reproductive system was so confusing to me with all it's little glands and pieces. I was going to draw just the male system to help me learn the terms, but I decided that drawing the entire thing would help me remember how the whole system works. The guy parts are in blue, the girl parts are in red and the steps of reproduction are in purple.