KS3 Bitesize: Science - Organisms, behaviour and health. Darwin's Theory Of Evolution. Cell Parts And Functions. Basic Anatomy - Organs & Organ Systems. There are many different types of cells in the human body. None of these cells function well on there own, they are part of the larger organism that is called - you. Cells group together in the body to form tissues - a collection of similar cells that group together to perform a specialized function.