Transcript Sci7-Ch2-ViewingCellsCellTheory

Do Now: The Dead Sea.
• Is the Dead Sea really dead?
Magnify…
Magnify…
Magnify…
• To increase the size of something
Lenses
• Enlarges images and directs light to
your eye
• Simple microscope
– one lens
• Compound microscope
– More than one lens
Compound Light Microscope
• Image viewed against a bright
background
• Often used in a laboratory
• Magnifies up to 430x
• These are the microscopes we have in
this classroom!
Compound light microscope
• Two sets of lenses
• 1. Eyepiece
– 10x magnification
• 2. Objective lenses
– 4x
– 10x
– 43x
Calculate magnification
• Eyepiece * objective = total magnification
• 10x * 4x = 40x
• 10x * 10x = 100x
• 10x * 43x = 430x
x
=
Antonie van
Leeuwenhoek
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Made a microscope
Used glass beads as the lens
Magnified 270x
Saw organisms in pond water
Fluorescence Microscope
• Treat the specimen with a dye
• Cell structures glow
• Magnifies up to 1500x
Do Now: They Might be Giants
Cells!
Scanning Electron Microscope (SEM)
• Sweeps beam of
electrons over a
specimen’s surface
• Uses a magnetic field
in a vacuum to direct
beams of electrons
• Show 3D images
Robert Hooke 1665
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First person to see cells using a microscope
Looked at cork
Only saw cell walls
When plant cells die only cell walls remain
Tree bark is dead tissue
Cork Hooke looked at came from a dead
oak tree
Robert Hooke 1665
• Cell Theory
– All living things are made of cells
• Could not see bacteria
– Did not stain slides
The Cell Theory
All organisms are made An organism can be one
of one or more cells
cell or many cells
The cell is the basic
unit of organization in
organisms
All cells come from
cells
Even in complex
organisms, the cell is the
basic unit of structure and
function
Most cells can divide to
form two new, identical
cells
Schleiden (1839)
• Viewed plant cells
• Organisms composed
of cells, the basic units
of life
Schwann (1839)
• Viewed animal cells
• Organisms
composed of cells,
the basic units of life
Virchow (1855)
• “every cell originates
from a pre-existing
cell”
The Cell Theory
• 1. all living things are composed of one
or more cells (Hooke)
• 2. cells are the basic units of structure
and function in an organism (Schleiden
& Schwann)
• 3. cells come only from the reproduction
of existing cells (Virchow)
Cell Shape
• Diversity in
shape reflects
function
• Shape can be
simple or
complex