Review and discuss with students the evidence underlying our saying that cells are the smallest unity of life. (They: take in nutrients and excrete wastes, grow, reproduce (cell division), and die. Many are capable of movement.)
Investigations reveal that every organ and tissue of the body is comprised of cells. A diagram showing the disposition of organs in the whole body may be found here: anatomy of whole body organs images
Let students choose various organs/tissues and examine photomicrographs (photographs taken under microscopes). Type into your browser: ________ photomicrographs enlarged to show cells images/ Insert the desired organ/tissue in the blank.
Conclusion: cells make up all organs/tissues of the body. Review how this occurs through cell growth, division, and differentiation (Lesson B-14)
Then: Organs and tissues make up the whole functioning body, the organism.