Read the given paragraph and answer the given question :
Parasitism has evolved in many taxonomic groups from plants to higher vertebrates. Many parasites have evolved to be host specific in such a way that both host and the parasite tend to co-evolve. In accordance with their life styles, parasite evolve special adaptations and complex life cycle.
Parasites harm the host by :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Reducing its survival, growth, reproduction and population density
Option (1) Reducing its size — Incorrect. It names only a small part of the harm and leaves out survival, reproduction and population density.
Option (2) Improving its growth and reproduction — Incorrect. A parasite benefits at the host's cost (+, −); it does not improve the host.
Option (3) Reducing its survival, growth, reproduction and population density — Correct. The harm to the host goes beyond its size: the passage names lower survival, growth and reproduction and a fall in the host’s population density. Only option (3) says all of this.
Option (4) Improving its survival, growth and reproduction — Incorrect. Improving the host’s survival and growth would make the partner a helper, as in mutualism where both gain. A parasite takes food and shelter from the host and harms it.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Population Interactions – “… The malarial parasite needs a vector (mosquito) to spread to other hosts. Majority of the parasites harm the host; they may reduce the survival, growth and reproduction of the host and reduce its population density. They might render the host more vulnerable to predation by making it physically weak.”