Biologi SMA

Viruses are not included in the classification system of 5 kingdoms, so they are generally grouped in a separate kingdom .Many scientists consider the viruses as “ The abridge of berween living things and the organism “. Viruses called organism because they are able to do live activities, namely metabolism and reproduction .However the activities can only happen if the viruses reside in living cells.

D.J. Ivanovsky (1852)

He was Russian botanist who succeeded in finding extract something from tobacco that had caught mosaic disease later , filtering extract through a filter with the very fine pores hoping to be able to catch all existing bacteria, yet it turned out that the extract was still able to infect other tobacco leaves .

Adolf Mayer ( 1870 – 1885 )

He was German microbiologist who succeeded in finding the yellow spot ( mosaic ) on tobacco leaf. According to him, the disease could infect other tobacco plants. To prove his analysis , he later spray the sap of the ill plant to a healthy one, apparently the healthy one became infected by the disease and his analysis proven.

Loffler and Frosch ( 1897 )

They were German scientists who succeeded in finding the viruses attacking animals where the viruses caused foot and mouth diseases to the animal.

Martinus Beijerink ( 1897)

He was the Dutch microbiologist who succeeded in finding the fact that the orgaof tobacco attacker could reproduce on the plant it lived on , but not could be reared in the medium of growth. Another fact which he found was that the organism did nit die when it was put in to alcohol .Based on the fact, finale the concluded that dilution from tobacco disease contained the organism called viruses.

Reed (1900)

He succeeded in finding the virus causing dengue disease in human being. This disease is propagated by Aedes aegypti mosquito as its medium.

Twort and d’Herelle (1916-1917)

They succeeded in finding the viruses attacking bacteria. These viruses could cause decomposition (lysis).

Wendell Stanley (1935)

He was a biochemist from the institute of Rockefeller, America, who succeeded in crystallizing TMV and indicated that the crystal consistanly could maintain their infection ability. It was hard to imagine that this could be conducted to organism. From that time on, the researches on viruses have kept developing.

Laidraw and stuart harris (1933-1936)

They succeeded is finding the influenza virus. They also concluded that if viruses were repeatedly put into experimental animal, it could influence their capacity to attack human beings.

Jonas salk (1953)

He succeeded in finding the preventative vaccine for the polio disease.

Characteristics of virus:

1. Viruses have two phases of existence, in their host cells and outside the host cells. If there are in their host cells, viruses can be called as organisms because their are able to reproduce, while if they are outside the host cells, viruses are not living.

2. Viruses cannot be included in one in the kingdoms in classification system of the five kingdoms.

3. All viruses have parasitic characteristic and are harmful for they host

4. Viruses consist of nucleic acid and capsid. Viruses with their mature parts are called virions

5. Each virion consist of a type nucleic acid (only DNA or RNA) and capsid. The nucleic acid generally only forms a single chain

6. The size of viruses is extremely small with diameter of about 20-400 nano meters (1 nanometer = 10^-9 meter), so viruses can only be seen by using electron microscope