Blood is created in bone marrow and is made up of cells suspended in liquid plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are cell fragments that allow blood to clot.

Anemia, which may cause weakness, dizziness, and headaches is caused by a lack of iron in the diet.

Capillaries are small thin-walled vessels that permit the exchange of oxygen, carbon dioxide, nutrients, and waste between blood and the body's cells. This process of exchange is called diffusion.

Newton's second law of motion states that The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object. This law basically means that the greater the mass of an object, the more force is needed to overcome its inertia.

Cells are classified into one of two groups based on whether or not they have a nucleus. Eukaryotic cells have a nucleus, prokaryotic cells do not have a nucleus and therefore have a less complex structure than eukaryotic cells.