1. Chapter 2.3
Discovering Cells

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

3. 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)

4. 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

5. 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?

6. POINT > Describe how different microscopes work
Magnification refers to the microscope’s power to increase an object’s apparent size

7. POINT > Describe how different microscopes work
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
40X 400X

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
200X 2000X

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. POINT > Describe the development of Cell Theory
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

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

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