1. Microscopes and Cells

2. Early Microscopes and the Cell Theory
Anton van Leeuwenhoek (1600’s) credited with the first microscope
Robert Hooke (1665) saw “cells” in woody plant tissue
Theodore Schwann (1839) saw cells in animal tissue

3. Cell Theory
Between 1839 and 1855 the nucleus of the cell was seen for the first time
Hypothesis was that the nucleus was involved in cell reproduction
Many observations were made of cell reproduction
Led to statement of the cell theory

4. Cell Theory All living things are composed of cells
All cells come from preexisting cells by cell division
The cell theory applies to all organisms
Single cell organisms
Multicellular organisms (many start life as a single cell)

5. Compound Microscope Major tool of modern biology
Compound means more than one lens
Ocular lens and objective lens
Magnification is the product of magnification power or the ocular and the objective
(10X) times (40X) = 400X

6. Compound Microscope Limitations to use of compound microscope
Samples need to be transparent or have to reflect a great deal of light
Many sample need to be sliced into thin sections and stained
Sectioning and staining involves chemical changes to the sample
Resolution limited by wavelength of light

7. Electron Microscope
Uses electron beam instead of light to examine the specimens
Magnification 1000X higher than the highest compound microscope
TEM and SEM
Specimen preparation is complex
Biologists study the pictures not the sample

8. Can you?
What do you say to someone who says they saw a living organism in the electron microscope at Liberty Science Center?
What do you say to someone who says that intestine cells are pink, magenta and dark purple because that’s what they saw in the microscope?

9. Two types of cells….
Prokaryote
No nucleus
Eukaryote
Nucleus