1. Cell Discovery & Cell Theory

2. It all started with an invention….  The first microscope  Zacharias Jansen, 1595, Middleburg, Holland  It launched great leaps in Astronomy and Biology.  Some of the first great observations with it were made by…

3. Robert Hooke (1635-1703)  Designed microscopes  Discovered and documented the first “cells” in 1665  Named them after the cells in which a monk sleeps.

4. Hooke released a book of detailed drawings and observations: Micrographia, 1665 Micrographia

5. Antony van Leeuwenhoek (1632-1723)  A tradesman from Holland who became fascinated with Hooke’s book  Discovered bacteria, free- living protists, sperm cells, blood cells, nematodes, etc.  Became an expert lens grinder and made over 500 simple microscopes  Acute eyesight and lens grinding skill let him build microscopes that were capable of 200X magnification

6. Antony van Leeuwenhoek... my work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men. And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof. Antony van Leeuwenhoek. Letter of June 12, 1716

7. Spontaneous Generation The theory that life comes from non-living matter. Francisco Redi in 1688 proved that flies do not come from rotting meat. Louis Pasteur in 1862 proved that microorganisms do not arise spontaneously from nutrient broths.

8. Beginnings of Cell Theory  1838 Mattias Schleiden stated that all plant tissues consisted of cells  1839 Theodore Schwann stated that all animal tissues consisted of cells  Each conjectured that there was a nucleus  1858 Rudolf Virchow combined the two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory

9. Rudolf Virchow 1821-1902 Cell Theory “every cell originates from another existing cell like it”  All living things are composed of one or more cells  In organisms, cells are the basic units of structure and function.  All cells are produced only from existing cells.

10. Modern Microscopes SSSSome of the light microscopes here are capable of 1000x magnification. TTTThat is about the limit of a light microscope’s magnification without losing clarity (called Resolving Power). DDDDue to the width of visible light’s wavelength TTTThe electron microscope was introduced in the 1950s and uses the wavelength of electrons to increase the resolving power by 100x. AAAApprox. 100,000x magnification!! CCCCell Biology advanced rapidly as cellular organelles were clearly seen for the first time.

11. Resolving Power

12. Electron Microscopes Works by scanning a beam of electrons over a prepared specimen. After passing over the object, scattered electrons are collected and formed into a 2-D or 3-D image.

13. Transmission Electron Microscope (TEM) magnifies a slice of a sample. (Rabbit trachea cilia) Scanning Electron Microscope (SEM) shows 3D image of the (Rabbit trachea cilia) Modern Microscopes

14. A modern TEM Limitations: Specimen must be prepared (killed). FOV very small. Very time consuming.

15. A Modern SEM

16. Fruit fly with four eyes under an SEM