The Cell Theory
Section 4.1
What do you know?
 Where are cells found?
 How many cells are there in a single human being?
 What do you think might be inside cells?
Living?
 Are these items living, once living, or nonliving?
 Autumn leaf
 Cotton shirt
 Tulip
 Steel beam
 Car
 Dog
 String beans
 Cow

How do you know which things are living?
Cells
 The basic unit of structure is the cell.
 All living things or things that were once living are
made up of one or more cells.
 Cells are difficult to see with the untrained eye.
 Cell- basic unit of function in all living things.
 Each cell carries out life processes.
Development of the Cell
Theory
 In 1675, a Dutch shopkeeper named Anton van
Leeuwenhoek, looked at pond water through a simple
microscope.
 He saw what he called “animalcules” (single-celled
organisms)
 Probably the first person to see cells.
Development of the Cell
Theory
 Around the same time, an English scientist and
inventor, Robert Hooke, used a crude compound
microscope to look at a very thin slice of cork.
 He saw “a great many little boxes”
 Why do you think he called them cells?
Development of the Cell
Theory

In the 1830’s a German botanist, Matthias Schleiden, noticed
that all the plants he observed under a microscope seemed to be
made of tiny units.

In 1838, he stated that all plants made up similar units (cells)

It was then discovered that cells were present in other living
things.

Another German scientists, Theodore Schwann, observed animal
tissue and stated that cells were the building blocks of both plants
and animals.


Pointed out that there were many different kinds of cells, each
with a different function.
In 1858, Rudolf Virchow, stated that all cells are produced only
by other living cells.
Development of the Cell
Theory
 The cell theory- set of statements about the ideas
about the cell.
 All living things are made up of one or more cells.
 Cells are the basic units of structure and function in
living things.
 All cells come only from other living things.
What have we learned?
1. Which scientist gave us the name “cell”?
2. What are the three parts to the cell theory?
3. Why is a cell considered the smallest thing that can be
called living?
4. Cells can be similar to bricks in a building. What other
things are like cells? Make a list. For each item,
explain how it is similar to a cell.