The study of the microscopic structure of a variety of animals, plants and microorganisms has led to the creation of the theory of cellular structure, which is mainly formed by the mid-nineteenth century. The main provisions of this theory are the following:
1) most organisms consists of many cells (multicellular) or represents one cell (unicellular);
2) when sexual and some forms of asexual reproduction individual life of every multicellular organism begins with a single cell;
3) despite significant differences in size and shape, the cells of all organisms have similarities in internal structure. The first study of cells refers to the beginning of the XVII century. Improvements light microscope, the researchers submerged deeper into the mysteries of the cell. Great importance for the development of science was the finding of cell division.
In our time, has significantly expanded the possibility of studying cell structure, functions, chemistry. In addition to the light microscope, which magnified 2500 times, constructed an electron microscope that magnifies objects in tens and hundreds of thousands of times. Therefore, when using the electron microscope you can see extremely fine details of the internal structure of the cell. Together with studies of fixed cells (i.e., pre-killed and processed in a special way) a proliferation of methods in vivo study. To study individual organelles of the cell are used powerful centrifuge, developing tens of thousands of rpm. The resulting centrifugal force separates from each other the constituent parts of cells with different density. Using all these methods able to better understand the functional meaning of the individual parts of the cell. This is facilitated by the study of the chemical composition of the whole cell and its various parts. The better we know the cage, the more you get evidence of a community of the organic world as a whole.
Except for multicellular and unicellular organisms are not cellular life forms — viruses and bacteriophages. These forms do not have a cellular structure and all its main functions of metabolism and reproduction is carried out only within the cells of another organism based on the same molecular structures (DNA and RNA) in organisms of the cellular structure. Viruses exert their activity in cells.
the Viruses and bacteriophages.
Viruses and bacteriophages, plant and animal, often causing serious diseases of these organisms (influenza, measles, polio and smallpox in humans; viral diseases of tobacco, potato, decorative and many other plants). Bacteriophages located in the body of the bacteria. Multiply inside bacteria cells, they lead her to death. Released from her bacteriophages are introduced to new, not yet infected with phages cells. Thus, bacteriophages — a kind of intracellular parasites of bacteria. In this regard, some Viruses and bacteriophages have been successfully used in medicine and veterinary medicine to combat bacterial diseases of humans and animals. Figure 1 shows some viruses and bacteriophages.