You will need play-doh, straws/sticks, and this recording sheet.
Challenge your students to create a human body, arm, or foot with just play-doh. Have them record their observations on the first sheet. The play-doh will not be able to stand, like the human body without bones. Give students the straw and have them recreate their body part. Have them record on the second sheet how this time it will stand because it has a "bone".