Download Microscopes and Cells

Microscopes and Cells
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
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
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)
Compound Microscope
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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
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
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
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?
Two types of cells….
• Prokaryote
– No nucleus
• Eukaryote
– Nucleus