The Cells | Learn About Cells Of Living Organisms | Elearnin скачать в хорошем качестве

The Cells | Learn About Cells Of Living Organisms | Elearnin

Cells are to a living organism just as bricks are to a building; they are the basic structural units. Though a building is built of similar bricks, they are of different shapes and sizes. In a similar fashion, all organisms are made up of cells, though they differ from one another. However, cells are more complex structures, unlike bricks. The egg of a hen is the best example of a cell, which can be seen by the naked eye. Scientists observe and study living cells using microscopes which can magnify objects. Dyes or stains are used as they help in studying a cell in detail by coloring the parts in a cell. There are millions of living organisms of different shapes and sizes. Their organs also vary in size, shape and the number of cells they contain. Let us now take a closer look at the number of cells in a body. The number of cells in every single organism runs into billions and trillions. The cells in a human body are of many types, sizes and shapes and perform a distinct variety of functions. Those organisms that are made up of more than one cell are called multi-cellular organisms. Multi means many and cellular means cell. The functioning of an organism, however, remains unaffected even if the number of cells in that organism is comparatively lesser. The life of every organism begins with a single cell. It is the fertilized egg that multiplies and thereby the number of cells increase as the organism develops. As such, there are also organisms that are made up of a single cell and are therefore called unicellular organisms. 'Uni' means one and cellular means cell. A unicellular organism can also carry out all those functions that a multicellular organism does. A single celled organism, such as the amoeba, can capture food, digest it, respire, excrete, grow and reproduce. Similar functions in multicellular are carried out by specific groups of specialized cells that form different tissues. These tissues, in turn, form the various organs.