4. Introduction to Digestion 2) Digestion is the breaking-down of food. It can be mechanical (chewing, tearing) or chemical (acids and enzymes).
5. Introduction to Digestion 3) Absorption occurs when nutrients are taken out of the food for the body. These projections absorb nutrients from food that brushes past them.
7. Introduction to Digestion Different animals have different digestive systems. For instance, jellyfish have "bag" systems. Some worms and birds must swallow rocks to help break-down food in their gizzards.