IMG_6843.jpeg

# UNIT 3 ## The Cell * A cell is the smallest unit of a living thing. * One of the most fundamental concepts in biology is that a cell is the basic unit of structure and function in living organisms. * A living thing, whether made of one cell or many cells is called an organism. Thus, cells are th...

# UNIT 3 ## The Cell * A cell is the smallest unit of a living thing. * One of the most fundamental concepts in biology is that a cell is the basic unit of structure and function in living organisms. * A living thing, whether made of one cell or many cells is called an organism. Thus, cells are the basic building blocks of all organisms. ## The Cell Theory * Cells are so small that their existence was unknown before the invention of the microscope. * In 1665, an English scientist named Robert Hooke made a microscope and looked at a piece of cork, the dead cells of oak park. * He observed tiny compartments and gave them the name 'cellulae', which means little rooms or cells. * After Robert Hooke, many improvements were made on both the type of microscopes and the techniques used to study the detail of cells. This started the new branch of biology called cytology (the study of cells). With the improved microscope, biologists have examined the internal structure of cells of different organisms. * In 1838, the German botanist Mathias Schleiden and Theodor Schwann, jointly stated that plants and animals are composed of identical structural and functional units called cells. * In 1859, the German physician Rudolf Virchow stated that cells come from pre-existing cells. * The statements of Schleiden, Schwann, and Virchow form the basis for the development of the cell theory.