Identify the statements that are false regarding the host-parasite relationship:
(A) Hosts and parasites typically co-evolve together.
(B) If the host develops specialised defences against the parasite, the parasite adapts to infect a different host species.
(C) If the host evolves mechanisms to resist the parasite, the parasite adapts to overcome these defences in order to continue infecting the same host species.
(D) Parasites have developed a complex nervous system for survival.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → B and D
Many parasites are host-specific, and the host and the parasite tend to co-evolve. If the host evolves a way to reject or resist the parasite, the parasite evolves a way to counter it, so that it stays successful with the same host species.
(A) Hosts and parasites typically co-evolve together. — True. This is co-evolution, as described above.
(B) If the host develops specialised defences against the parasite, the parasite adapts to infect a different host species. — False. The parasite does not switch to another host. It evolves mechanisms to counteract and neutralise the defences and stays with the same host species.
(C) If the host evolves mechanisms to resist the parasite, the parasite adapts to overcome these defences in order to continue infecting the same host species. — True. This is the book’s description of how the parasite responds.
(D) Parasites have developed a complex nervous system for survival. — False. Parasite adaptations go the other way: loss of unnecessary sense organs, adhesive organs or suckers, loss of the digestive system and high reproductive capacity. A complex nervous system is not one of them.
So the false statements are B and D.
NCERT Extract:
Population Interactions – “… Many parasites have evolved to be host-specific (they can parasitise only a single species of host) in such a way that both host and the parasite tend to co-evolve; that is, if the host evolves special mechanisms for rejecting or resisting the parasite, the parasite has to evolve mechanisms to counteract and neutralise them, in order to be successful with the same host species. In accordance with their life styles, parasites evolved special adaptations such as the loss of unnecessary sense organs, presence of adhesive organs or suckers to cling on to the host, loss of digestive system and high reproductive capacity.”