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7-1 Life Is Cellular
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7-1 Life Is Cellular
The Discovery of the Cell
The Discovery of the Cell
The existence of cells was unknown for most of
human history.
WHY?
No one could see them!
This changed with the invention of the microscope.
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7-1 Life Is Cellular
The Discovery of the Cell
Early Microscopes
In 1665, Robert Hooke used an early compound
microscope to look at a thin slice of cork, a plant
material.
Cork looked like thousands of tiny, empty
chambers.
Hooke called these chambers “cells.”
Cells are the basic units of life.
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7-1 Life Is Cellular
The Discovery of the Cell
Hooke’s Drawing of Cork Cells
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7-1 Life Is Cellular
The Discovery of the Cell
At the same time, Anton van Leeuwenhoek used a
single-lens microscope to observe pond water and
other things.
The microscope revealed a world of tiny living
organisms.
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7-1 Life Is Cellular
The Discovery of the Cell
What is the cell theory?
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The Discovery of the Cell
The Cell Theory – Important Scientists
In 1838, Matthias Schleiden concluded that all
plants were made of cells.
In 1839, Theodor Schwann stated that all animals
were made of cells.
In 1855, Rudolph Virchow concluded that new
cells were created only from the reproduction of
existing cells.
These discoveries led to the cell theory.
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7-1 Life Is Cellular
The Discovery of the Cell
The cell theory states:
• 1. All living things are composed of cells.
• 2. Cells are the basic units of structure
and function in living things.
• 3. New cells are produced from existing
cells.
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Exploring the Cell
Exploring the Cell
New technologies allow researchers to study the
structure and movement of living cells in great
detail.
The microscope is one of the greatest inventions in
the advancement of cell biology today.
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7-1 Life Is Cellular
Microscopes
The van Leeuwenhoek microscope
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7-1 Life Is Cellular
Microscopes
This is an original van Leeuwenhoek
microscope preserved in his home town of
Delft. It is about the size of a postage stamp.
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Microscopes
Microscopes through the years:
1680
1725
1750
1875
1828
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7-1 Life Is Cellular
Microscopes
Electron Microscopes
Electron microscopes reveal details 1000 times
smaller than those visible in light microscopes.
Electron microscopy can be used to visualize only
nonliving, preserved cells and tissues.
Antarctic mite
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Microscopes
Modern
Compound
Light
Microscope
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7-1 Life Is Cellular
Microscopes
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Microscopes
Eyepiece
Body Tube
Revolving Nosepiece
Arm
High Power Objective
Low Power Objective
Diaphragm
Stage Clips
Stage
Coarse Adjustment
Light
Source
Fine Adjustment
Base
Switch
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7-1 Life Is Cellular
Microscopes
1.
2.
9.
3.
10.
11.
12.
4.
5.
6
13.
7.
14.
8.
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Microscopes
Carrying
Your
Microscope
Correctly
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7-1 Life Is Cellular
Microscope
Incorrectly
Carrying
Your
Microscope
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Microscopes
Putting Your Microscope Away
Storing your scope for use the next time
requires that you follow a few easy steps –
REMOVE THE SLIDE FROM THE STAGE
-Dispose of the specimen as directed by your
teacher.
-Clean the slide and cover slip
-Return the slide and cover slip to its proper place.
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Microscopes
Always Store Your Scope on 10X.
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7-1 Life Is Cellular
Microscopes
Unplug Your Scope Correctly.
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7-1 Life Is Cellular
Microscope
Wind the Cord Around the Base.
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7-1 Life Is Cellular
Microscope
Cover Your Scope Before
Returning It.
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Prokaryotes and Eukaryotes
Types of Cells
Cells come in a variety of shapes and sizes.
All cells:
• are surrounded by a barrier called a cell
membrane.
• at some point contain DNA.
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Prokaryotes and Eukaryotes
Cells are classified into two categories based upon
whether or not they contain a nucleus.
Eukaryotes are cells that contain a nucleus.
Prokaryotes are cells that do not contain a nucleus.
The nucleus is the structure that contains the cell's
DNA and controls many of the cell's activities.
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Prokaryotes and Eukaryotes
What are the characteristics of
prokaryotes and eukaryotes?
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Prokaryotes and Eukaryotes
Prokaryotes
Prokaryotic cells have genetic material
that is not contained in a nucleus.
Prokaryotes do not have membrane-bound
organelles.
Prokaryotic cells are generally smaller and
simpler than eukaryotic cells.
Bacteria are prokaryotes.
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Prokaryotes and Eukaryotes
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Eukaryotes
Eukaryotic cells contain a nucleus in
which their genetic material is separated
from the rest of the cell.
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7-1 Life Is Cellular
Prokaryotes and Eukaryotes
Eukaryotic cells are generally larger and more
complex than prokaryotic cells.
Eukaryotic cells generally contain dozens of
structures and internal membranes.
Many eukaryotic cells are highly specialized.
Plants, animals, fungi, and protists are eukaryotes.
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The cell theory states that new cells are
produced from
a. nonliving material.
b. existing cells.
c. cytoplasm.
d. animals.
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The person who first used the term cell was
a. Matthias Schleiden.
b. Lynn Margulis.
c. Anton van Leeuwenhoek.
d. Robert Hooke.
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Electron microscopes are capable of revealing
more details than light microscopes because
a. electron microscopes can be used with live
organisms.
b. light microscopes cannot be used to
examine thin tissues.
c. the wavelengths of electrons are longer
than those of light.
d. the wavelengths of electrons are shorter
than those of light.
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Which organism listed is a prokaryote?
a. protist
b. bacterium
c. fungus
d. plant
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One way prokaryotes differ from eukaryotes is
that they
a. contain DNA, which carries biological
information.
b. have a surrounding barrier called a cell
membrane.
c. do not have a membrane separating DNA
from the rest of the cell.
d. are usually larger and more complex.
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END OF SECTION