1. Life Is Cellular All living things are made of cells.

2. Microscopes enable the human eye to observe cells, the smallest units of life.

3. There are many important scientists who have made discoveries that have helped to uncover the mystery of cells. Let’s take a look…

4. Robert Hooke was the originator of the word “cell” in biology. He used the microscope pictured here to observe thin slices of cork. His observations of these plant cells reminded him of monks' cells which were called "cellula." Robert Hooke (18 July 1635 - 3 March 1703) – natural philosopher, inventor, architect....

5. Leeuwenhoek's skill at grinding lenses enabled him to build microscopes that magnified over 200 times. He was the first to observe life in a drop of pond water. In a letter Leeuwenhoek described observations of lake water, including an excellent description of the green algae Spirogyra : "Passing just lately over this lake,... and examining this water next day, I found floating therein…some green streaks, spirally wound serpent-wise…The whole circumference of each of these streaks was about the thickness of a hair of one's head... all consisted of very small green globules joined together: and there were very many small green globules as well." Antony van Leeuwenhoek (1632-1723)

6. Matthias Jakob Schleiden April 5, 1804 - June 23, 1881 In 1838 Schleiden discovered that ALL plants are composed of cells; together with his friend Theodor Schwann he formulated the cell theory of life.

7. Theodor Schwann December 7, 1810 – January 11, 1882 In Schwann discovered that ALL animals are also composed of cells. He worked with Matthias Schleiden to formulate the cell theory.

8. Rudolf Virchow October 13, 1821 - September 5, 1902 Virchow's many discoveries include cells in bone and connective tissue. In 1855 he published his idea that "every cell stems from another cell.” He also stated that all diseases involve changes in normal cells.

9. These discoveries lead to what we call The Cell Theory. The Cell Theory states that: 1.All living things are composed of cells. 2.Cells are the basic units of structure and function in living things. 3.New cells are produced from preexisting cells.

10. Two Types of Cells ProkaryotesEukaryotes Do NOT have a nucleusDO have a nucleus Smaller and simpler cellsMore complex cells with dozens of specialized organelles All bacteria are prokaryotic cellsAll plant, animal and fungi are made of eukaryotic cells. Carry out all activities of life even though they are simple organisms. They do not contain all the membrane bound organelles. Each organelle plays a role in carrying out life processes and maintaining homeostasis.