Cells
Cell can be defined as the structural and functional unit of life. It could also be describe as the simplest and basic unit of life in which are living organism are made of cells.
Classification of Living Organism Based on the Number of Cells
These includes;
1. Unicellular Organism: These are organism which consists of only one cells e.g. Amoeba, Paramecium.
2. Multi-cellular Organism: These are organism which consist of two or many cells e.g. flowering plant, bird, hydra.
History of Cell
Many scientist have contributed to the distribution of history of cell which are listed below
1. Robert Hooke: He is regarded as the father of cell. He was the first human being to discover the honey comb structure of the cell in 1665.In his book, Micrographic, he described his observation of a slice of a cork of an oak tree. He established that the cork is made up of thin components or rooms which he later named the components of cells.
2. Felix Dujardin: He was a French biologist in 1835, which he discovered that the cell was made up of living substance. He however named the living substance protoplasm.
3. Matthias Schledien: He is also a German botanist in 1838 revealed that the bodies of plants are made of cells which were described as units of life.
4. Theodor Schwann: He was also a German zoologist in 1839; He discovered that the bodies of all animals are composed of cells.
5. Rudolf Von Virchow: He was also a German biologist in 1855, concluded in his research that all cells come from previously existing cells.
The Cell Theory
These include;
1. The cell is the structural and functional unit of life.
2. All living organisms are made of cells
3. All cells come from previously existing cells.
4. There is no life apart from the life of cells.
5. All living things are either single cells or multicellular cell.
Forms in Which Living Cells Exist
These include;
1. As Independent or Single and Free Living Organism
This means that organism that possesses only one cell and is capable of living freely on their own. E.g. Amoeba, Paramecium.
2. As a Colony: This means that some organism are made of many similar cells which are joined or massed together but they cannot be differentiated from each other .e .g Volvox, Pandorina etc.
3. As a Filament: This simply that certain cells are organised into filaments. Each cells functions as an independent living cell. E.g. Spirogyra, Zygnema.
4. Cells as Part of a Living Organism: This means that in multi-cellular organism, a group of numerous, similar cells are arranged together and specific function is called a tissue. A group of similar tissue forming a layer in an organism which performs a specific function is called an organ. A group of organs which works together to perform specific function is called a system.
Differences between Colonial Organisation and Filamentous Organisation
|
Colonial Organism |
Filamentous Organism |
|
1. There is absence of intercellular wall. |
There is presence intercellular wall. |
|
2. The identical cells form a mass. |
The identical cells form end to end arrangement in linear form. |
Tests and Exercises
1. Who is regarded as the father of cell? (a) Robert Jude (b) Robert Hooke (c) Robert Lamarck (d) Robert Johnson.
2. How many forms does living cells exist? (a) 3 (b) 5 (c) 6 (d) 4.
3. Living organisms that exhibit only one cell are called (a) Unicellular (b) Tri cellular (c) Bi-cellular (d) Di-cellular.
4. The basic structure and fundamental unit of life which living organism exists is called (a) Genetic (b) Cell (c) Cytogenetic (d) Anatomy.
5. A group of organ which works together to perform specific function is called (a) Cell (b) Organ (c) System (d) Tissue.
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