Transcript THINK ABOUT IT

Lesson Overview
7.1 Life is Cellular
Lesson Overview
Life Is Cellular
Early Microscopes
It was not until the mid-1600s that scientists began
to use microscopes to observe living things. The
research of a few famous scientists led to the
development of The Cell Theory.
Robert Hooke (England-1665)
• Used an early compound microscope to look at
a nonliving thin slice of cork (plant material)
• He observed thousands of tiny, empty chambers
• He described the empty chambers as ‘cells,’
like those that monks in a monastery lived in
• The term cell is still used in biology to this day
• We now know that living cells are not empty
chambers, but contain many working parts,
each with its own function
Lesson Overview
Life Is Cellular
Early Microscopes
Anton van Leeuwenhoek (Holland-1674)
• He observed tiny living organisms in
drops of pond water and other things,
including a sample of saliva
• He drew the organisms he saw in the
mouth—which today we call bacteria
Lesson Overview
Life Is Cellular
The Cell Theory
Soon after Leeuwenhoek, observations made by
other scientists made it clear that cells were
the basic units of life.
Matthias Schleiden (German Botanist-1838)
• concluded that all plants are made of cells
Theodor Schwann (German Biologist-1839)
• stated that all animals were made of cells
Rudolf Virchow (German Physician-1855)
• concluded that new cells could be produced
from the division of existing cells
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Lesson Overview
Life Is Cellular
The Cell Theory
These discoveries are summarized in the cell theory, a fundamental
concept of biology.
The cell theory states:
• All living things are made up of cells.
• Cells are the basic units of structure and function in living things.
• New cells are produced from existing cells.
Lesson Overview
Life Is Cellular
Exploring the Cell
• Light microscope-allows light to pass through a specimen and uses two
lenses to form an image.
• Stains or dyes help scientists see the structures within the cells.
• Electron microscope-use beams of electrons that are focused by magnetic
fields.
• Offers a much higher resolution and allows scientists to view much
smaller things.
– Transmission electron microscope-make it possible to explore cell
structures and large protein molecules.
• Produces flat, two-dimensional images.
– Scanning electron microscope-a pencil-like beam of electrons is
scanned over the surface of a specimen.
• Produces three-dimensional images of the specimen’s surface.
• Electron microscopy can be used to examine only nonliving cells
and tissues.
Lesson Overview
Life Is Cellular
Prokaryotes and Eukaryotes
Typical cells range from 5 to 50 micrometers.
• The smallest Mycoplasma bacteria are only 0.2 micrometers across and
difficult to see under even the best light microscopes.
• The giant amoeba Chaos chaos may be 1000 micrometers in diameter,
large enough to be seen with the unaided eye as a tiny speck in pond
water.
Despite their differences, all cells contain the molecule that carries
biological information—DNA.
In addition, all cells are surrounded by a thin, flexible barrier called a cell
membrane.
Lesson Overview
Life Is Cellular
Prokaryotes
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Oldest
Smaller and simpler
Do not enclose DNA in nuclei-NO nucleus!
Lack membrane bound organelles
Ex. Bacteria
Despite their simplicity, prokaryotes grow, reproduce, and respond to the
environment, and some can even move by gliding along surfaces or
swimming through liquids.
Lesson Overview
Life Is Cellular
Eukaryotes
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Larger and more complex
Enclose their DNA in nuclei-Nucleus present!
Contain membrane bound organelles
Ex. Plants, animals, fungi, and organisms commonly called “protists”