Includes practice questions on viruses, viroids, prions, and lichens, covering their structure, classification, and significance in biology.
Bacteriophages are viruses that infect bacteria. They are usually double-stranded DNA viruses, and their nucleic acid is protected by a protein coat called the capsid.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
W. M. Stanley demonstrated in 1935 that viruses could be crystallised. The crystals consisted largely of proteins, and viruses were found to remain inert outside their specific host cells.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
Lichens do not grow in polluted areas. Therefore, their absence from a locality can indicate the presence of environmental pollution.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
Viruses contain genetic material in the form of either RNA or DNA. No virus contains both RNA and DNA. The nucleic acid is enclosed by a protein coat called the capsid.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
Viroids are infectious agents made of low-molecular-weight RNA. They lack the protein coat found in viruses and were discovered by T. O. Diener.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The particle is a virus. Viruses remain inert outside their specific host cells but take over the host-cell machinery after infection to produce additional virus particles.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The agent is a viroid. T. O. Diener discovered viroids while studying potato spindle tuber disease. Viroids consist of free RNA of low molecular weight and lack the protein coat found in viruses.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The organism is a lichen. Its algal phycobiont prepares food, while its fungal mycobiont provides shelter and absorbs water and mineral nutrients. Lichens do not grow in polluted areas and therefore indicate air pollution.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The agent is a viroid. Viroids consist of free RNA of low molecular weight and lack the protein coat found in viruses. T. O. Diener discovered them while studying potato spindle tuber disease.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
A viroid consists of free RNA of low molecular weight and lacks a protein coat. A prion is an infectious agent composed of abnormally folded protein and contains no nucleic acid.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The agent is a viroid. T. O. Diener discovered viroids while studying potato spindle tuber disease. Viroids consist of free RNA of low molecular weight and lack the protein coat present in viruses.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
The organism is a lichen. The algal phycobiont prepares food, while the fungal mycobiont provides shelter and absorbs water and mineral nutrients. Lichens do not grow in polluted areas and therefore indicate air pollution.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
