The Cell Theory: a Brief History
Robert Hooke 1635-1703
Invented the first microscope
Viewed slices of cork and called it “cellula” (little rooms)
Antoni Van Leeuwenhoek 1632-1723
Worked with glass à huge improvement in quality of lenses à nearly 300x magnification became possible
First to observe:
Single-celled organisms “animalcules” protists from pond water bacteria from his mouth – was considered “father of microbiology” blood cells banded pattern in muscle cells sperm from ...
Progress stalled for a century or so ... limited resolving power emphasis on description rather than explanation
1830s – compound microscope improved magnification and resolution allowed visualization of objects less than 1 μm
1833 Robert Brown (botanist – studies plants) noticed that every plant cell contained a round structure
1838 Matthias Schleiden (another botanist) all plant tissues are composed of cells embryonic plant always arose from a single cell
1839 Theodor Schwann (zoologist – studies animals) similar observations in animal cells recognition of structural similarities btw plants and animals!
Cell Theory formulated by Schwann all organisms consist of one or more cells the cell is the basic unit of structure for all organisms added 20 years later: all cells arise only from pre-existing cells
Facts and the Scientific Method: fact: something we know to be true … something we believe to be true … fact (scientific): an attempt to state our best current understanding, based on observations and experiments valid only until revised or replaced by a better understanding, based on more careful observations or more discriminating experiments
What is the scientific method?
Make observations or gather information to create a tentative hypothesis
Make predictions based on your hypothesis
Carry out controlled experiments to test your hypothesis and make further observations
Interpret results – do they support your hypothesis?
What is a theory?
A hypothesis that has been tested critically under many different conditions, by many people using a variety of approaches
When an explanation is regarded as a theory, it is widely accepted by most scientists
“solid ground” of science – evolution, germ theory, cell theory
If a theory is thoroughly tested and confirmed over many years by such large numbers of investigators that there is no doubt of its validity … it may eventually be regarded as a law.
For example, the law of gravity, thermodynamics and gas laws. Biologists are very conservative about using the term law
- Hooke looks at cork coming up with the cell
- Cytology- bed rock of cell bio
- Cells actually do chemistry
- Mendel – monk who did the pea plant experiment
- Where all three strands come together is the modern time
- DIC = differential