1. + Chapter 2, Section 3 Discovering Cells

2. + An Overview of Cells Cells: the basic units of structure and function in living things Cells and Structure How cells are put together and the shape that forms Cells and Function Obtaining oxygen, getting rid of wastes, obtaining food, and growing

3. + First Observations of Cells 1590 The invention of the microscope made it possible for people to discover and learn about cells Microscope: an instrument that makes small objects look larger SIMPLE MICROSCOPE: one lens COMPOUND MICROSCOPE: more than one lens

4. + Robert Hooke One of the first people to observe cells Built his own compound microscope Used this microscope to observe thin slice of cork Looked like tiny rectangular rooms, called them cells meaning “small rooms”

5. + Anton van Leeuwenhoek About the same time as Hooke Built a simple microscope Used this microscope to observe lake water, scrapings from teeth and gums, and water from rain gutters He noticed that many of the things he observed were ONE-CELLED He called the moving organisms he saw ANIMALCULES (“little animals”)

6. + Development of the Cell Theory Three scientists worked together… Schleiden Concluded all plants are made of cells Schwann Concluded that all animals are also made of cells THEREFORE, all living things are made up of cells Virchow New cells are formed only from cells that already exist “All cells come from cells”

7. + The Cell Theory The cell theory is a widely accepted explanation of the relationship between cells and living things 1. All living things are composed of cells 2. Cells are the basic units of structure and function in living things 3. All cells are produced from other cells

8. + Magnification and Lenses Lenses in light microscopes magnify an object by BENDING the light that passes through them Convex lens: magnifying glass and hand lenses Middle of lens is thicker Outside of lens is thinner

9. + Compound Microscope Magnification Lenses of a LIGHT microscope… Light passes through specimen Then through two lenses 1 st lens near specimen magnifies object 2 nd lens near the eye further enlarges object Example: One lens makes an object 10 times larger, second lens makes an object 40 times larger TOTAL: 10 X 40 = 400

10. + Resolution Being able to clearly distinguish the individual parts of an object Or…sharpness of an image

11. + Electron Microscope Electron microscope uses a beam of electrons instead of light to produce a magnified image The resolution is much better than the resolution of a light microscope