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.

The acids produced by the pancreas contain several enzymes that aid in digestion.  Lipase converts fat to glycerol and fatty acids. Pancreatic amylase breaks down complex carbohydrates into simple sugars. Trypsin converts polypeptides (the building blocks of protein) into amino acids.

The nucleus of a eukaryotic cell contains the genetic material of the cell and is surrounded by cytoplasm which contains many organelles.

Primary consumers (herbivores) subsist on producers like plants and fungus.  Examples are grasshoppers, cows, and plankton.

The broadest classification of life splits all organisms into three groups called domains. The three domains of life are bacteria, archaea and eukaryota.