T H E S C I E N T I S T S T H A T M A D E C E L L
D I S C O V E R Y P O S S I B L E

Anton van Leeuwenhoek
 Discovered single-celled, animal-like organisms, now called protozoans.

Hans and Zacharias Janssen
 Invent the first compound microscope by placing two lenses in a tube.

Robert Hooke
 Observes cork and names the tiny chambers that he see cells. He publishes drawings of cells, fleas, and other minute bodies in his book Micrographia.

Matthias Schleiden

Studied plant tissues and concluded that all plants are composed of cells.

Theodor Schwann

Studied animal tissues and concluded that they consisted of cells.

Rudolph Virchow

Proposed that all cells are produced from the division of existing cells.

Louis Pasteur

Pioneered the study of bacteria using compound microscopes.

First, what is a cell?!
It took a long time for people to discover cells and figure out what they were all about.
They need sophisticated equipment
(microscopes) to be able to see cells.
Every thing we know about cells we call
“cell theory”.

Cell Theory says that….
1. All living things are made of cells.
2. Cells are the basic units of structure and function in all living things. In other words, cells are like the building blocks of all living things.
3. New cells are only made from existing cells.

Introduction to Cells

HOW DO YOU KNOW IF
SOMETHING IS ALIVE?
TALK TO THE PEOPLE AT
YOUR TABLE AND COME UP
WITH A DEFINITION OF
“LIFE”.

Eight Characteristics of Life



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Made of one or more cells
Displays organization
Grows and develops
Reproduces

Responds to stimuli
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Requires energy
Maintains homeostasis
Adapts