Cell is considered as the smallest unit of life. Each living organism is made up of one or more cells. Cell biology or the science of cells is known as cytology. But the two terms cell biology and psychology is not the same meaning. Cytology specially refers study of structure and composition of sales whereas cell biology includes study of both structured and function sales and the relation between them.
As the cells are the smallest unit of life and most of them are too small to be seen with naked eyes, some tools and techniques are required to study their structures. In the field of cytology and most important tool is the microscope.
Different types of microscope: –
A microscope is comparable to human eye. We know that both human eye and the microscope have the systems of lens and in both cases images of the object are formed. The construction and utility of the microscope is based on the
principle of getting a magnified image of the object through the lenses. Microscope used in biological study especially study of smallest unit of life, the cell are mainly of two types, those are light microscope and electron microscope. The light microscope in the biological laboratory of schools and colleges whereas from microscope for research and higher studies.
All living organisms are composter of cells which we called the smallest unit of life that originate from pre-existing cells. An organism may be made up of only one cell or number of many cells. Those organisms which are made up of one single cell only are called unicellular organism. Examples of such unicellular organism are the bacteria, Chlamydomonas, Yeast, Amoeba etc. Otherwise those organisms which are made up of more than one cells, are called multi-cellular organisms. Numbered of sales in multi-cellular organism may be only a few cells to several billions cells. As example of such multi-cellular organism we may say the big trees, human beings and large animals like Tiger, cow, elephant etc. The life of every organism, whether plant or animal, begins as a single cell and so the cell is called the smallest unit of life.
We unicellular organism Complete there are entire life cycle as a single cell, while multi-cellular organisms begin their life form just a single cell which in course of life divides deadly the number of sales for forming the multi-cell body. Thus the cells are considered as the structural units of a living body. Each cell has its own function and in the multi-cellular organism, a number of different types of cell of different functionalities are exit together. So, the activities of such an organism are the sum of total coordinated activities of its component cells. Thus the cells are not only the smallest unit of life but also the functional units of the life.
In a multi-cellular organism, certain cells become specialized to perform some specific functions. The cells which have a common origin and similar specific functionality constitute a tissue. Different types of tissues collectively form an organ and every organ performs some specific functions. A group of organs performing some specific functions together constitute a organ system, such as the digestive system, respiratory system, reproductive system, etc. Each cell exhibits all the characteristics of life such as respiration, metabolism, growth, reproduction, etc. through the components of the cell. So the smallest unit of life is the cell or the cell is the structural and functional unit of life.
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