I  will present the different blood cells and their tasks: red blood cells carry oxygen, white blood cells fight germs, and platelets form clots.  We will also be talking about plasma and its components.
The blood types and consequences of "mixing " blood.  We will talk about the different illnesses you can get from too little or not enough cells. It will be a one-time class. It will be relaxed. Learners can interact, and no previous experience or knowledge needed.
I think the class would be most enjoyed by students who have an interest in biology.