2. Chapter 2.3 Discovering Cells

3. POINT > Identify how cells were discovered POINT > Describe how different microscopes work POINT > Describe the development of Cell Theory

4. POINT > Identify how cells were discovered The invention of the lens Robert Hooke (1665): observed a thin slice of cork (dead plant cells) with a microscope. He described what he observed as “little boxes” (cells).

5. POINT > Identify how cells were discovered Anton van Leeuwenhoek (1675): was the first person to observe living cells. He was looking at pond water and saw “miniature animals” swimming around

6. CHECK: Who was the first person to see cells? What was Robert Hooke looking at with his microscope? What was van Leeuwenhoek looking at when he first saw living cells?

7. POINT > Describe how different microscopes work Magnification refers to the microscope’s power to increase an object’s apparent size Resolution refers to the microscope’s power to show detail clearly

9. POINT > Describe different microscopes The compound microscope uses two lenses to magnify objects

10. CHECK: What is magnification? What is resolution? How many lenses in a compound microscope?

11. POINT > Describe different microscopes Elodea (aquatic plant) with a light microscope 40X400X

12. Transmission Electron Microscope (TEM)

13. Transmission Electron Microscope (TEM) gives better resolution Herpes Virus Plant Root Cell

14. Scanning Electron Microscope (SEM)

15. Scanning Electron Microscope (SEM) shows even better topography Mosquito Head 200X2000X

16. Scanning Electron Microscope (SEM) Fly Eye

17. Scanning Electron Microscope (SEM) Inside of Stomach Surface of Tongue Neuron

18. Scanning Electron Microscope (SEM) Pollen Yeast Red Blood Cell, Platelet, and White Blood Cell

19. TEM vs. SEM Viruses leaving a cell

20. Who developed the Cell Theory? Matthias Schleiden (1838): concluded that all plants are composed of cells Theodor Schwann (1839): concluded that all animals are composed of cells Rudolph Virchow (1855): determined that cells come only from other cells POINT > Describe the development of Cell Theory

21. What is the Cell Theory? 1.All living things are composed of one or more cells. 2.Cells are organisms’ basic units of structure and function. 3.Cells come only from existing cells. POINT > Describe the development of Cell Theory

22. Homework: Read pages 50-57 GRAS pages 31-33