Q5. What did Beijerinck call the infectious fluid from diseased tobacco plants, and what does it mean?
Contagium vivum fluidum, infectious living fluid (NCERT page 20).
Q6. What did W.M. Stanley show about viruses?
That viruses could be crystallised, and that the crystals consist largely of proteins (NCERT page 20).
Q7. What kind of genetic material do bacteriophages usually have?
Double-stranded DNA (NCERT page 20).
Q8. Which disease did T.O. Diener find to be caused by a viroid, and in which year?
Potato spindle tuber disease, in 1971 (NCERT page 21).
Q9. Name four viral diseases of human beings given by NCERT.
Mumps, small pox, herpes and influenza; AIDS is also caused by a virus (NCERT page 20).
Q10. Assertion: viruses are called obligate parasites. Reason: they are inert outside their specific host cell. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: a virus can replicate only inside a living host cell, using the host’s machinery (NCERT page 20).
Q11. What does the word virus mean?
Venom or poisonous fluid (NCERT page 20).
Q12. Why do lichens not appear in Whittaker’s five kingdoms?
NCERT gives no reason; it notes only that the five kingdom classification makes no mention of lichens (page 19). A lichen is an association rather than a separate kingdom; its fungal and photosynthetic partners retain their taxonomic placements.