Virus

Size->20-30mm/50 times smaller than bacteria

Characters of Virus

Living Characters Non-living Character

1.Nucleic acid surrounded by protein coat. Lacks cellular structure.

2.Can grow and reproduce in host cell. Lack enzyme system.

3.Undergoes mutation. Doesn’t respire

4.Shows intracellular parasitism. Some of them can be crystallized and stored in bottle.

5.Redponds to light, chemicals and temperature. High specific gravity.

Classification of Virus

1. Animal virus Eg. Polio virus, Corona virus, rabies virus, etc.

2. Plant virus Eg. TMV, PMV, etc.

3. Bacteriophage virus ie.virus infecting bacterial cells.

On the basis of DNA-RNA as genetic material

1. DNA virus

2. RNA virus

3. DNA-RNA virus

Economic importance

1. They are used as models in genetic structures.

2. Some of them may be beautifully variegated.

3. May destroy bacterial cells and make water free from them.

4. Bacteriophage virus can be used in treatment of several diseases like cholera.

Negative aspects

1. Causes numerous diseases in plants and animals.