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Which one of the following is categorised as a parasite in true sense?
A
The cuckoo (koel) lays its eggs in crow's nest
B
The female $Anopheles$ bites and sucks blood from humans
C
Human foetus developing inside the uterus draws nourishment from the mother
D
Head louse living on the human scalp as well as laying eggs on human hair
Detailed Solution
A true parasite lives on or in the host, obtains its food from the host and usually completes its life cycle there, harming the host.
The head louse lives on the human scalp, feeds on human blood and also lays its eggs on the hair; it is an ectoparasite in the true sense.
The female $Anopheles$ needs blood only for reproduction and visits the host just to feed; NCERT states that the female mosquito is not considered a parasite.
The koel laying eggs in the crow's nest is brood parasitism, in which only parental care is exploited.
A foetus drawing nourishment from its mother is a normal part of reproduction of the same species, not parasitism.
Hence the true parasite is the head louse.
The head louse lives on the human scalp, feeds on human blood and also lays its eggs on the hair; it is an ectoparasite in the true sense.
The female $Anopheles$ needs blood only for reproduction and visits the host just to feed; NCERT states that the female mosquito is not considered a parasite.
The koel laying eggs in the crow's nest is brood parasitism, in which only parental care is exploited.
A foetus drawing nourishment from its mother is a normal part of reproduction of the same species, not parasitism.
Hence the true parasite is the head louse.