**Human Body Systems Sorting Activity** This low-prep sort activity is the perfect way to have your students learn the levels of organization from smallest to largest in the human body. It includes picture examples of the four levels of organization for six body systems (circulatory, digestive, excretory, muscular, nervous, and respiratory). The pictures come in 3 different sizes, two with labels. Use the category cards and the larger pictures in your science center or station, use the sorting