The Cell Theory
Essential Question #1
What was science like
before the invention of
the microscope?
What Science Believed…
In the 16th century doctors rarely touched
their patients. They just studied their
excreta (bodily fluids) instead.

Common Practices:
Blood letting
Leeches
Reading fluids
Medical Wisdom of the
Century
th
16
God implanted the soul in the embryo forty days after
conception. The soul controlled growth and nutrition,
sensation and motion, and all rational activity.
Women were nothing more than imperfect versions of
men.
Diagnoses could be made from the nature of excrement,
and tint of skin
The liver created blood, which was used by the brain to
create invisible nervous spirits which flowed through the
nervous system and were vectors of sensation and
motion.
Beliefs About Life…
Scientists believed in
Spontaneous
Generation.
Example: Scientists believed
that maggots come from rotting
meat and mice come from
grain.
What We Know Now…
Life can only come from other
living things!

Francesco Redi designed a
brilliant controlled experiment.
Essential Question #2
How did the invention of
the microscope
change science?
Microscope History
1590- Zacharias Jenssen: built the first
microscope.
Microscopes Continued
Robert Hooke: made
improvements to
Jenssen’s
microscope.

Why is this important?
Hooke and Cells!
Hooke came up with
the term “Cell” after
looking at the cell
walls of plants.

The box-like cells of
cork reminded Hooke
of the cells of a
monastery.
Can You See What Hooke Saw?
1675: Antony van Leeuwenhoek
Leeuwenhoek:
constructed a simple
microscope that could
magnify objects as
much as 270 times.

He was the first to
see…?
Essential Question #3
What are the components
of the Cell Theory?
The Cell Theory
1. All living things are composed of cells.
1. Cells are the basic unit of life
(structure and function).
1. Cells come from preexisting cells.
You Already Knew…
Plants and animals are made up of cells.

It is one of the five characteristics of life:
All living things are made up of cells.

All living things have cellular organization.
Science Didn’t Until…
Matthias Schleiden: concluded that all
plants are composed of cells.
Theodore Schwann: concluded that all
animals are composed of cells.
Schleiden and Plants
When you weed your
garden, you are
uprooting plants from
the soil.

Schleiden was the first
scientists to say that
those plants are made
up of cells.
Schleiden is Weedin’
Schwann and Animals
Schwann was the first
scientists to say that
all animals are
composed of at least
one cell.
Schwann’s Swans
Together…
Brief History of Cells
Quick Quiz
Put these items in order in terms of which
came first in the scientific study of living
things:
____ DNA
____ Light Microscope
____ Electron Microscope
____ Cell Theory
____ Discovery of Cells
Quiz Answer
Put these items in order in terms of which came
first in the scientific study of living things:
1. Light Microscope
2. Discovery of Cells
3. Cell Theory
4. DNA
5. Electron Microscope