The Cell Theory
Some Random Cell Facts 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!!!
Visualizing Cells
Light Microscope Can observe living cells Less Expensive Don t magnify as much as an E.M. Resolution Magnification Objective x eyepiece Rules: 1. Always carry using 2 hands, one on the base, the other holding the arm 2. Never use coarse adj. in med or high power 3. Never clean the lenses with anything other than lens paper 4. Always turn the microscopes off and put a cover over them when not in use
Electron Microscopes Can magnify much higher than light microscopes Very expensive Big and non-portable 2 types S.E.M. (scanning) T.E.M. (transmission)
Scanning Electron Microscope (S.E.M.) Shows an image of the scanned surface Useful for looking at 3-D structure of specimens Butterfly Eye S.E.M. 22,000X
Transmission Electron Microscope (T.E.M.) Shows a cross section view of specimens Useful for viewing the insides Plant Leaf T.E.M. 42,000x
Discovery of Cells 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi
Anton van Leuwenhoek 1673- Used a handmade microscope to observe pond scum & discovered singlecelled organisms He called them animalcules He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants
150-200 Year Gap??? Between the Hooke/Leuwenhoek discoveries and the mid 19 th century, very little cell advancements were made. This is probably due to the widely accepted, traditional belief in Spontaneous Generation.
Spontaneous Generation For much of history, people believed that animals could come from non-living sources. Historical documents contain recipes for creating creatures such as: bees, frogs, mice, etc. These recipes were based on observations. When the Nile river flooded, soon many frogs appeared in the mud. If damp rags were left in a pile of wheat grain, many mice appeared 21 days later.
Jar-1 Left open: Maggots developed Flies were observed laying eggs on the meat in the open jar Jar-2 Covered with netting: Maggots appeared on the netting Flies were observed laying eggs on the netting Jar-3 Sealed: No maggots developed Francisco Redi
Lazzaro Spallanzani (1767) Set up an experiment to test whether a vital force in the air could give rise to microorganisms. Spallanzani s hypothesis: Beef broth becomes cloudy due to bacteria present in the air. The bacteria from the air enter the broth and contaminate it, rather than the bacteria arising from the air or broth itself.
Spallanzani s Experiment
The Big Prize The Paris Academy of Science offered a prize to the person who could best resolve the spontaneous generation debate once and for all. And the winner was Louis Pasteur (1864): A scientist who designed an experiment using a flask that would allow air containing the vital force to enter the flask, but would keep microorganisms out.
Louis Pasteur Broth Experiment
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.
Development of Cell Theory 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.
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)(1838-39) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)