Microbiology is one of the Biology Topics that involves the study of microorganisms, including bacteria, viruses, and fungi.
Discovery of Cells and Cell Theory
While studying a thin slice of cork, Robert Hooke saw that the cork resembled the structure of a honeycomb consisting of many little compartments. Cork is a substance that is obtained from the bark of a tree. This was in the year 1665 when Hooke made this chance discovery through a self-designed microscope. Robert Hooke called these boxes cells. Cell in Latin means “little room”. Robert Hooke’s discovery was important because it indicated for the first time that living organisms consisted of a number of smaller structures or units.
Cell Theory – Definition, History, Importance, Scientists
The word cell is derived from the Latin word ‘cellula’ which means “a little room”. An English scientist, Robert Hooke (1635 – 1703), in 1665 discovered and named the cells, while examining a thin slice of bottle cork under a primitive microscope made by him. Hooke observed the cork’s honeycombed or porous structure. Hooke found the porous structure of cork to resemble monasteries and called the units, cells. He published his work in a book “Micrographia” in 1665.
In 1674, Anton von Leeuwenhoek (1632 – 1723), a Dutch microscopist, made an improved microscope, and using this microscope he discovered the free living cells in pond water for the first time (1674). In 1678, he discovered sperm and identified the sperm cells of humans, dogs, rabbits, frogs, fish, and insects.
However, Hooke had only seen the thickened walls of the cells and not the substance contained within these walls. In 1831, a Scottish botanist, Robert Brown (1773 – 1858) discovered and named the nucleus in plant cells. J.E. Purkinje (1787 – 1869), a Czech animal physiologist, in 1839 gave the term protoplasm for the living fluid substance present inside the cell. In 1866, Haeckel established that the nucleus was responsible for storing and transmitting hereditary characters.
In 1838, Jakob Matthias Schleiden (1804 – 1881), a German botanist, first proposed the idea that all plants consist of cells. A year later, in 1839, Theodor Schwann (1810 – 1882), a German zoologist, independently asserted that all animals and plants are made up of cells. This joint finding forms the basis of the cell theory.
The cell theory was refined further in 1855, when another German biologist, R. Virchow presented the idea that all cells arise from pre-existing cells (His actual aphorism was ‘Omnis cellulae a cellula’). Thus, the cell theory comprises the following postulates:
- All organisms are composed of cells and cell products (e.g., secretions).
- All metabolic reactions take place in cells. Thus, cells are structural and functional units of life.
- All cells arise from pre-existing cells only. No cell can originate spontaneously or de novo (anew) but comes into being only by division of already existing cells.
- Every organism starts its life as a single cell. Viruses are an exception to the cell theory.