Cell History and Microscopy Presentation
Overview
This presentation provides background information on the
discovery of cells and the cell theory. It introduces key
scientists who were influential in these historical scientific
advancements. The presentation also provides a collection of
microscope images of plant and animal cells, elodea leaves,
and several pond-dwelling organisms. The microscope
images depict 40 and 100 magnifications.
The Discovery of Cells
Cells are very small and they are not easily viewed
using only your eyes.
How did scientists
discover cells?
Microscopes
An early microscope.
In the late 1500s, scientists
used lenses to create
instruments that would
magnify small objects and
organisms. They called
these tools microscopes.
Microscopes gave scientists
a window into the
microscopic world.
Robert Hooke (1635–1703)
Robert Hooke was a scientist
who used a microscope to look
at thin sections of cork. Hooke
observed that cork is made up
of tiny, boxlike spaces. These
spaces reminded Hooke of the
small rooms, or cells, in a
monastery, so he called the
compartments “cells.”
Robert Hooke’s drawing of cork cells.
Anton van Leeuwenhoek (1632–1723)
The cork cells that Robert
Hooke studied were no longer
alive. Anton van Leeuwenhoek
was the first scientist to observe
living cells under a microscope.
Leeuwenhoek saw active
unicellular organisms in a drop
of pond water. He also observed
live bacterial cells obtained
from teeth scrapings.
Image courtesy of the National Library of Medicine.
The Importance of Cells
Robert Hooke and Anton van Leeuwenhoek were among
the first scientists to study cells. However, the importance
of cells was not known until more than 150 years later.
Why are cells
so important?
The Importance of Cells
In the 1800s, the quality of
microscopes improved
greatly. This allowed
scientists to observe cells
in even more detail.
Scientists began to develop
the idea that the cell is the
basic unit of life.
Matthias Schleiden (1804–1881)
Matthias Schleiden was a
botanist who used a
microscope to study plant
tissues. Through his
observations, he concluded
that plants are made of cells.
Theodor Schwann (1810–1882)
A zoologist named Theodor
Schwann applied
Schleiden’s use of the
microscope to animal tissue.
He determined that animals
are also made of cells.
Rudolf Virchow (1821–1902)
Rudolf Virchow
determined that all cells
come from existing cells
through a process of cell
division.
The Cell Theory
The cell theory incorporates the ideas of Schleiden,
Schwann, and Virchow. The cell theory states:
* All living things are made up of one or
more cells.
* The cell is the basic unit of structure and
function in all organisms.
* Cells come from existing cells.
Microscopy
The following slides show images of cells and
microscopic organisms as viewed through modern
microscopes.
Microscope Image
Cork Cells
This is a microscope image of plant cells from cork.
Microscope Image
Onion Cells
This is a microscope image of plant cells from an onion.
Microscope Image
Human Cheek Cell
This is a microscope image of an animal cell.
Microscope Images of Elodea Leaf
40 magnification
100 magnification
cell
Elodea is a multicellular, aquatic (water) plant.
Can you see individual cells in the images above?
Microscope Images of Pond Organisms
40 magnification
spirogyra
volvox
Volvox is a multicellular, freshwater organism made up of
thousands of individual cells. Spirogyra is a multicellular,
strand-like organism that also lives in fresh water. The tiny
specks in the images are unicellular (single-celled) organisms.
Microscope Images of Pond Organisms
40 magnification
planarian
Planaria are multicellular flatworms that live in fresh water.
Can you see the planarian’s eyes?
Microscope Images of Pond Organisms
40 magnification
hydra
Hydra is a multicellular, freshwater organism. It has
tentacles for catching smaller organisms to eat.
Microscope Images of Pond Organisms
40 magnification
daphnia
Daphnia are multicellular organisms called water fleas.
Can you see the daphnia’s eyes and internal organs?
Microscope Images of Pond Organisms
100 magnification
spirogyra
volvox and spirogyra
The higher magnification in these images and on the
following slides reveals small organisms in more detail.
Microscope Images of Pond Organisms
100 magnification
spirogyra and
unicellular organisms
planarian head
and eyes
Microscope Images of Pond Organisms
100 magnification
hydra tentacle
daphnia