Post on 05-Jan-2016
All living things are made of one or
more CELLS.
Some organisms consist of ONE cell
while others have MANY cells.
Regardless of the number of cells, living things must carry on all the life PROCESSES.
This cell is in the process of cell REPRODUCTION.
Since cells cannot be seen with the naked eye, the invention of the…..MICROSCOPE was very important to the discovery of cells.
It was not until the mid-1600’s that microscopes were used to examine the parts of living things.
One of the first scientists to use a compound microscope was…..
ROBERT HOOKE who examined thin slices of CORK and other plant tissues.
He found that they contained BOXLIKE structures which he called CELLS.
What Hooke saw, however, were the walls of….
…DEAD cells.
He never observed the cells of living things.
Anton van Leeuwenhoek examined drops of….
POND water using a very powerful single-lens microscope.
Leeuwenhoek also observed human BLOOD cells and BACTERIA which are the smallest kinds of cells.
It was not until the early 1800’s that the cellular nature of living things began to gain attention. 1824 – Henry
Dutrochet
Proposed that all living things were made from cells.
1831 – Robert Brown
Observed and named the NUCLEUS
Schleiden and Schwann
1838 – Matthias Schleiden
Developed the theory that all plants contained cells.
1839 – Theodor Schwann
Proposed that all animals contained cells.
Purkinje and Virchow
1839 – Johannes Purkinje
Used the term “protoplasm” to refer to the jelly-like material in a cell.
1855 – Rudolf Virchow
Stated that all living cells came from other cells.
Schultze and Dujardin
1861 – Max Schultze
Defined “protoplasm” as the physical basis of life.
1861 – Felix Dujardin
Recognized the existence of one-celled organisms.
By the end of the 1800’s scientists discovered many structures that lie WITHIN a cell. They were also able to describe the events of cell DIVISION in which one cell splits to form TWO cells.
As a result of the work of these scientists, the main points of the CELL THEORY were stated.
The Cell Theory states that….
› All organisms are made of ONE or more CELLS
› All cells carry on LIFE ACTIVITIES
› New cells ARISE only from other LIVING cells by the process of CELL DIVISION.
There are THREE (3) exceptions to the cell theory.
The first cell could not have come from a pre-existing cell.
Although viruses can carry on many life processes, they DO NOT contain cells
Mitochondria and chloroplasts contain their own DNA and can reproduce within a cell.