For a bonus project, have students ask their parents to help them learn about thier leaf. They can find out a few simple facts, draw a picture, write a sentence, and be the teacher for the rest of the class.
Take a nature walk and have students pick one kind of leaf. Then follow these directions on how to make an imprint with clay. They can take home a "Leaf Token" as a keepsake at the end of the unit.
Students who finish early could try drawing the structures of blood. If the teacher can obtain the materials, looking through a microscope at real slides of blood and draw that for a further extension.
This activity lets students create a simple and safe model of human blood. It provides a way to make something microscopic easier for children to understand.