Status of Viruses: Viruses are at the borderline of living and nonliving. They show characteristics both like living and non living.
Living characteristics of viruses: **They have nucliec acids (DNA OR RNA).
** They show reproduction.
** show sensitivity.
Non-Living characteristics: **They can be crystallized.
** In non living environment they show no sensitivity.
** They are A-cellular.
Prions are composed of protein only and Viroids are composed of circular RNA only. Both these particles cause infectious diseases in certain plants. These are excluded from five kingdom system of classification due to both living and non-living characteristics.
Position of virus in five kingdom system or why viruses are excluded from five kingdom system of classification: viruses are excluded from five kingdom system of classification due to both living and non living characteristics.