- Quotes from referenced book
- Notes from Lectures
- Futher Reading
Introduction to Degree Level Cells
Before looking into the different types of Cell and how Cells and life forms are catagorised, it is important to understand what a cell is. A cell is described as :
"The basic structural and functional unit of living organism; the smallest structure capable of performing the essential functions characteristic of life" (Becker's world of the cell), There is a simplification of this deffinition which says "The Cell is the basic unit of biology"
To better understand this deffinition consider this. Every organism eaither consists of Cells or is itself a Cell. This means that everything living, including you, the plants in your garden, the annoying loud people next door and the teacher you see every day, are all composed of Cells.
The meaning of the word Cell comes from the latin word Cellula which translates into Little room. When Cells were first discovered their importance and role was not realised and so, they were compared to a small room, in that little coule be seen inside them, and they were small.
More on cells Discovery
How cells were discovered:
A scientist named Robert Hooke, built a microscope and used it to examin slices of cork cut with a pen knife. It was while doing this he noticed that when magnified, the cork was actualy composed of tiny little compartments.
Hooke did not understand what he was seeing, ofcourse he did not know what a cell was and simply noticed that the cork was made of compartments. But later on when looking at a plant cell, Hooke noticed that the cell was full of some kind of fluid.
The microscope used by Hooke only had a magnification of X30, ofcourse the magnification could of been increased but this reduced the resolution so much that it made looking at the cell impossible. So because of this the components of the cell were not discovered untill some time after.
The Tree of Life
When looking at how different organisms are catagorised we use something called the tree of life. As all organisms are composed of cells, the tree of life is also composed of different types of cells.
This is shown below
The above Phylogenetic tree shows the relationship betwen all cells and it also shows the three different types of cells. Bacteria, Archaea and Eukaryota.
We're going to be looking at Bacteria and Eukaryotes.
Prokaryotes and Eukaryotes
Although above, Bacteria are shown as making up one third of the tree, this is technicaly not correct as bacteria are part of the group known as Prokaryote. A Prokaryote is: - Any cell that does not contain a true nucleus or any other organelles. Where as a Eukaryote is: …