Biology teacher

  NCERT Class 11 Biology: Viruses, Viroids, Prions and Lichens Explained Simply - Dr.Sanjaykumar Pawar  Viruses Viruses are acellular (non-cellular) Comparison of Viruses, Viroids, Prions, and Lichens showing structure, composition, and biological roles in Class 11 Biology. organisms . They are not considered fully living because they do not have a cellular structure. Outside a host cell, viruses remain inactive and crystalline (non-living form) . Inside a living cell, they become active and use host machinery to reproduce . They are called obligate intracellular parasites (can live and reproduce only inside host cells). They kill or damage host cells during reproduction. The word virus means “poisonous fluid” . Discovery of Viruses (Important for exams) Dmitri Ivanovsky (1892) discovered microbes causing tobacco mosaic disease. These agents were smaller than bacteria and passed through bacteria-proof filters. M.W. Beijerinck (1898) named them “virus” a...