Chapter 3: Cell Structure and Function

Section 3.1 – History of Cytology

Objective:

Identify the scientists that helped discover the cell theory.Discuss the importance of the invention of the microscope.

History of the CytologyMany people feel

that Anton van Leeuwenhoek

invented the first microscope.

However this has been disputed in

recent years - Zacharias Jansen is now thought to

be the original inventor in 1595.

History of the CytologyDuring the 1600’s, Leeuwenhoek used his microscopes to look at drops of pond water and other liquids.He discovered that the water contained tiny living things.

Animalcules

History of CytologyAt about the same time Robert Hooke, English physicist, used a microscope to observe plants.He pointed out that the woody parts (cork) of plants contained tiny rectangular chambers, which he called cells.

History of CytologyIn 1839, German biologist Theodor Schwann, found that some animal tissues closely resembled the circular tissues of plants.As he observed the tissues with better and better microscopes, he concluded that animals are composed of cells as well.

History of CytologyAlso during this time, Robert Brown discovered an object near the center of many cells – the nucleus.German biologist Matthias Schleiden expanded on Brown’s work, suggesting that the cell’s nucleus plays a role in cell reproduction.

History of CytologyIn 1855, German physician Rudolf Virchow proposed that animal and plant cells are produced only by cell division.

The discoveries and observations of these scientists make up what is now known as the cell theory.

Cell TheoryAll living things are composed of cells.Cells are the smallest working units of living things.All cells come from preexisting cells by cell division.