Introduction To Cell
The cell is defined as the smallest structural and functional unit of life. It is a complex unit which performs a variety of functions. The credit to the discovery of cells goes to Robert Hooke in 1665. He with the help of microscope was able to locate honeycomb-like structures in a slice of cork. These structures were compartmentalized and were separated from each other.
Discovery of a cell date back to 1665 and is supposed to be one of the major discovery after an improvement in resolution as well as magnification of microscopes. Cell shows a variety of shape, size, and counting and they differ for different organism depending upon the function it requires to perform.
Today million of cells are known with a variety of shape and sizes. These variations are as a result of a variety of functions performed by cells. Cells are generally divided into two groups based on a number of cells present namely unicellular and multicellular.
Unicellular: (uni: one; cellular: cell) Organism made up of single cells are known as unicellular eg: ameba, paramecium etc. All the necessary functions are performed by this single cell.
Multicellular: ( multi: many; cellular: cell)Organism made up of more than one kind of cells are known as multicellular. In this type group of specialized cells are made to carry out specific functions.
Shape of cells
Cells are known to occur in many shapes viz. spherical (Red Blood Cells), elongated, spindle-shaped (muscle cells), branched (nerve cells) etc. There are certain cells which have no definite shape i.e. the shape keeps on changing e.g. ameba which is a unicellular organism with projections protruding out of the main body. These projections are known as Pseudopodia (pseudo: false; podia: feet).
Size of cells
Different sized cells are known to exist with size ranging from few micrometers to as large as few centimeters. Cells are not visible by naked eyes and can only be seen using a microscope. The smallest sized cell was known is around 0.1-0.5 micrometer in few bacteria with the largest cell being that of an ostrich egg measuring 170mm × 130mm.
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