Microscopes and Cells

1
Microscopes and Cells
2
Early Microscopes and the Cell Theory

• Anton van Leeuwenhoek (1600s) 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 thats what they saw in the microscope?

9
Two types of cells.

• Prokaryote
• No nucleus
• Eukaryote
• Nucleus