Chapter 7

Section 1

Discovery of Cells

The Cell Theory

• The Cell Theory states that all organisms are composed of similar units of organization called cells.

Before the Cell Theory people believed in spontaneous generation which means living things come from non living thing

Two scientist disproved spontaneous generation.

Francisco Redi proved that macroorganisms do not spontaneously generate

People thought that maggots came from meat.•Redi disproved this in a controlled experiment

Pasture proved that microoganisms do not spontaneously generate

Pasture

Development of Cell Theory

• Theodor Schwann and Matthias Schleiden are credited with coming up with the Cell Theory

Schwann•   Animal Cells

Schleiden•Plant Cells

The Cell Theory  1. All known living things are made up

of cells.

2. The cell is structural & functional unit of all living things..

3. All cells come from pre-existing cells by division.(No spontaneous generation ).

Microscopes

• The Cell Theory would not exist if it wasn’t for the development of the microscope and the work of others.

Janssen

• Invented the first compound microscope

Robert Hooke

• In 1663 an English scientist, Robert Hook improved Janssen’s invention.

Hooke

• Hooke observed cork – the remains of dead tree bark

• Coined the word CELL

• Derived from the Latin 'cellula' which means small compartment.

Van Leeuwenhoek

• Ten years later Anton van Leeuwenhoek used his own single lens microscopes and was the first person to observe bacteria and protozoa.

Leeuwenhoek’s Microscope

• Leeuwenhoek microscopes resemble high power magnifying lenses.

Compound Light Microscope

• Ocular lens times objective lens give total magnification

Two Basic Cell Types

• Prokaryotic Cells Mainly single celled organisms

• Eukaryotic Cells Mainly multicellular organisms, although some are single celled (amoeba,algae, yeast)

Prokaryotic Cell

• Prokaryotes have no membrane bound organelles.

• Example – bacteria cell

Eukaryotic Cells

• Eukaryotes – contain membrane bound organelles

• Example – plant and animal cells

Organelles• An organelle is a small

specialized structure inside of a cell.

• An example of an organelle is the nucleus which controls cell functions.