According to the passage, many new diseases are emerging due to change in land use because
- (a)humans are coming in contact with unfamiliar viruses
- (b)urbanisation makes pathogens proliferate
- (c)humans become adaptive and pass on their genes to related bacteria by way of plasmid transfer
- (d)humans are inadvertently releasing new viruses
Correct — A, humans are coming in contact with unfamiliar viruses. When land use changes — forests cleared, wild areas settled — people and their animals move into habitats where they meet wildlife and its pathogens for the first time, so previously unfamiliar viruses jump to humans and cause new diseases. This is the direct chain from 'change in land use' to 'new diseases'. Option C describes an unrelated bacterial mechanism (plasmid transfer, and humans don't pass genes to bacteria), while B and D assert proliferation or accidental release that the land-use-contact link does not require.
- (b)urbanisation makes pathogens proliferate — Urbanisation is a different process from 'change in land use' contact, and multiplying existing pathogens is not the same as new diseases emerging from novel contact.
- (c)humans become adaptive and pass on their genes to related bacteria by way of plasmid transfer — Biologically wrong direction — humans do not transfer their genes to bacteria; plasmid transfer is bacteria-to-bacteria and has nothing to do with land use.
- (d)humans are inadvertently releasing new viruses — The mechanism is exposure to existing wildlife viruses through new contact, not humans 'releasing' viruses.
Reading comprehension — cause/mechanism: link the stated cause ('change in land use') to the answer that supplies the biological mechanism (new human contact with wildlife/unfamiliar viruses causing spillover); reject options with wrong or unrelated mechanisms.
No directly related past PYQ was found.
- practice — not a real PYQ
Zoonotic diseases (e.g. from bats or rodents) most often reach humans when:
- (a)people avoid all wild areas
- (b)human activity brings people into closer contact with wildlife
- (c)vaccines are widely used
- (d)antibiotics are stopped
Answer(b) human activity brings people into closer contact with wildlife — enabling spillover of animal pathogens.
- practice — not a real PYQ
In the phrase 'a spillover event', the pathogen typically moves from:
- (a)one human to another only
- (b)an animal reservoir to humans
- (c)plants to soil
- (d)water to air
Answer(b) an animal reservoir to humans.