1. Meet the Scientists
Unit 5
Lesson 1

2. What is a cell?
The cell is a basic building block of living things.

3. All living things have cells.
Plants
Animals

4. Cell trivia
The average human being is composed of around 100 Trillion individual cells!!!
It would take as many as 50 cells to cover the area of a dot on the letter “i”
WOW!!!

5. Cell Theory
All organisms are composed (made up of) cells.

6. Tool used to view cells
A microscope is an instrument that makes small objects APPEAR bigger
Simple microscope has 1 lens
Compound microscope has 2 lenses

7. First sightings of cells
Until the late 1500’s there was no way to see cells. No one even knew they existed.

8. Timeline
Hans and Zacharias Janssen (1590), Dutch lens grinders, father and son. Produced first compound microscope (2 lenses).

9. Timeline- 1665
Robert Hooke (1665), English Scientist, looked at a thin slice of cork through a compound microscope and observed tiny, hollow room like structures. He called them cells, but only saw the outer cell walls because the cork cells were not alive.

10. Timeline-1680
Anton van Leeuwenhook (1680), Dutch Amateur Scientist, looked at blood, rain water and scrapings from teeth through a simple microscope
He called these bacteria.

11. Time Gap
Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made.
This is probably due to the widely accepted, traditional belief in Spontaneous Generation.
Examples:
-Mice from dirty clothes/corn husks
-Maggots from rotting meat

12. Time Gap Spontaneous Generation.
In the mid 1600, an Italian doctor named Francesco Redi, designed controlled experiments to show that flies do not spontaneously arise from decaying meat.
People still believed in spontaneous generation

13. 19th Century Advancement
Much doubt existed around Spontaneous Generation
Conclusively disproved by Louis Pasteur in the mid 1800’s ? = +

14. Timeline-1838
Matthias Schleiden (1838), German Botanist, viewed plant parts under a microscope and discovered that they are made of cells.

15. Timeline-1839
Theodor Schwann (1839), German Zoologist, viewed animals parts under a microscope and discovered that they are made of cells.

16. Development of Cell Theory
1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells
1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

17. Timeline- 1855
Rudolph Virchow (1855), German Physician, stated that living cells come only from other living cells.
Plant Cells
Animal Cells

18. The Cell Theory Complete
The 3 Basic Components of the Cell Theory were now complete:
1. All organisms are composed of one or more cells. (Schleiden & Schwann)( )
2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)( )
3. All cells are produced by the division of preexisting cells. (Virchow)(1858)

19. Some Parting Thoughts
It is amazing to think that the cells that make up our bodies are just as alive as we are.
All living organisms are just an intricately designed community of cells, which must work together to survive.