1.Explain how is small intestine designed to absorb digested food. 2.Write two differences between the nutrition in amoeba and human beings.
3.Fungus can be harmful and useful. Give an example showing both of these traits of fungus.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.