Theory:

Virus in Latin means 'poison'. Viruses are very tiny organisms 10,000 times smaller than bacteria.
Viruses are the reason for many communicable diseases.
Epidemics and pandemics are caused by viruses such as 'Ebola' and COVID-19.
Viruses are obligate parasites or holoparasites. This type of parasites require a host to complete its life-cycle. Without a host, an obligate virus cannot reproduce.
Structure
  • Virus has a simple structure.
  • It has an outer cover of protein inside which there is a core genetic material either DNA or RNA.
  • Viruses have different shapes, like rod, spherical, helical, etc.
virus types.PNG
 
  • Some viruses have spikes made up of lipids or carbohydrates. These spikes help them to attach to hosts. The image below shows the coronavirus with spikes.
 
corona-5025003_1920.jpg
Characteristics
Viruses show both the characteristics of a living organism as well as non-living organism. The table below summarizes their characteristics:
 
Living characteristicsNon-living characteristics
Viruses reproduce like living thingsThey are acellular and thus have no cytoplasm or cellular organelles
Viruses can mutateViruses do not grow
Viruses respond to heat and cold They can be crystalized and stored like a material
Viruses are influenced by chemical and radiationThey are inactive if present in the environment like dust particles
 
Important!
Do you know:
What is the study of viruses called?
Virology!