Viruses & its Types in Biology
Virus is Latin word which means poison.
Discovery:
Viruses were discovered by lwanowsky in 1892 from infected leaves of tobacco.
Living or Non-living:
They have characteristics of living and non-living things. When they enter in the body of living organisms they reproduce like living things. But when they are outside of the body they form crystals like non-living things.
Size & Shape:
Their size is from 0.01m to 0.3m. They are rounded, rod shaped, polyhedral and tadpoles in shape.
Structure:
They are chemically alike and have two parts:
- i) An outer coat of protein. This coat determines the shape of virus. It consists of two parts Head & Tail.
- ii) An inner core of DNA or RNA. DNA is present in head region. Animal viruses contain DNA and plant viruses have RNA.
Nutrition:
They cannot prepare their own food. All viruses are parasites and obtain food from host.
Reproduction:
They reproduce when they enter in the body of host.
Diseases:
- i) In plants virus cause many diseases. For example ring spot in many plants. Yellow in sugar beet and mosaic in tobacco, potato and tomato etc.
- ii) In animals virus cause mouth and food diseases. Cowpox in horses and cows.
iii) In human virus cause cold, influenza, smallpox, polio, hepatitis, cancer and AIDs etc.
Sources of Transmission:
- i) Through droplets due to coughing.
- ii) Through droplets due to sneezing.
iii) Through physical contact.
- iv) By air and contaminated water and food.
- v) By re-use of already used syringes.
- vi) By un-sterilized surgery equipments
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