Reference Notes | SLC
Virus – Characteristics and Transmission
For: Science Class 10
Virus is a very tiny, infections and highly pathogenic organisms, which can multiply only within the living host. They don’t have cellular structure. They contain hereditary material in the form of DNA or RNA enclosed in a protein coat called capsid. A mature virus is called a viron.
They exhibit properties of both living and non-living things, as Virus has no metabolic activity of its own. They are smallest living organism with the size of about 20 nm to 300 nm. Based on the host they attack, viruses are of 3 types.
- Animal Virus
- Plant Virus
- Bacteriophages
They are also classified into RNA virus and DNA virus on the basis of nucleic acid present in them.
Q. Why is a virus considered as the boarder line between living and non living things?
Ans: Virus is a living thing only inside a cell and nonliving thing outside a cell so it is considered as a chain between living and non living things.
Q. Why are viruses called obligatory parasite?
Ans: Viruses are called obligatory parasite because they are fully dependent on the other organisms.
Structure of Bacteriophase:
Characteristics/ Nature of Virus:
- They don’t show respiration & metabolism
- They can reproduce only inside living cell.
- They don’t show cellular structure.
- They are like molecules.
- They show host specificity i.e. particular virus can attack only a particular host
Transmission of Virus:
Virus transmits by means of air, water and food particles. When an infected person sneezes, virus from the water droplets enter the near by healthy person. Viruses also transmit by blood and body fluids. Some common viral diseases, organs affected medium & control measures are shown in the table below.
Name of the diseaseName of VirusOrgans effectedMediumControl MeasuresCommon coldRhino virusUpper respiratory tractSalivaControl of infectionMumpsParmyxo virusRespiratory tractSalivaControl of infectionMeaslesParmyxo virusMouth, Skin, Instestine and Respiratory tractSalivaControl of infectionPolioPolio virusPharynx, Intestine, Blood and BrainFeaces, SalivaPolio dropsRabiesRabies virusSpinal cord, brainSalivaAnti rabies vaccineAIDSRetro virusSkin, Blood and BrainUnsafe sex, BloodAvoid sex with multiple partners, Use condoms
Q. Culture of virus is impossible, why?
Ans: Culture of virus is impossible because it is very minute and it is alive inside host only.