biology : class12 Anopheles Vector : Causative Organism, Plasmodium, Life Cycle, Symptoms, Prevention : Malaria MCQ Questions and Answers
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Anopheles Vector
MCQ questions and answers.
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MCQ Questions
1. Which combination most reliably distinguishes the malaria vector from the non-vector adult mosquito in the genus Anopheles?
A.
The female has plumose antennae and the male has simple antennae
B.
The female has a long proboscis and palps nearly as long as the proboscis, whereas the male has plumose antennae
C.
The female has short palps and the male has a long, piercing proboscis
D.
Both sexes have equally developed piercing mouthparts, but only the male transmits parasites
Correct Answer:
The female has a long proboscis and palps nearly as long as the proboscis, whereas the male has plumose antennae
Explanation:
Only female Anopheles mosquitoes take blood meals and act as malaria vectors. In Anopheles, the female palps are approximately as long as the proboscis, while males have characteristically plumose antennae and do not blood-feed.
2. A mosquito is observed resting on a wall with its body and proboscis held at an acute angle to the surface. Which conclusion is most justified?
A.
It is likely an Anopheles mosquito, because this resting posture is characteristic of the genus
B.
It is certainly a male mosquito, because males rest obliquely
C.
It is a Culex mosquito, because Anopheles rests parallel to surfaces
D.
It cannot transmit malaria, because an angled resting posture prevents blood-feeding
Correct Answer:
It is likely an Anopheles mosquito, because this resting posture is characteristic of the genus
Explanation:
Adult Anopheles commonly rests with its body angled away from the surface, unlike the more parallel resting posture typical of Culex. This is a useful morphological clue for identifying the malaria-vector genus, although sex must still be determined separately.
3. Which feature of a female Anopheles most directly explains why it, rather than the male, can serve as a malaria vector?
A.
Its ability to feed on blood using piercing and sucking mouthparts
B.
Its possession of branched antennae for detecting stagnant water
C.
Its consumption of nectar during flight
D.
Its shorter life span compared with the male
Correct Answer:
Its ability to feed on blood using piercing and sucking mouthparts
Explanation:
The female Anopheles requires a blood meal for egg development and can acquire and transmit Plasmodium during successive blood meals. Males feed mainly on plant juices and therefore do not transmit malaria.
4. Why is the female Anopheles described as a biological vector rather than merely a mechanical carrier of Plasmodium?
A.
Plasmodium multiplies and undergoes developmental changes inside the mosquito
B.
The mosquito transports Plasmodium only on the outer surface of its legs
C.
The mosquito kills Plasmodium before it reaches a human host
D.
Plasmodium reproduces only in the mosquito's breeding water and not inside its body
Correct Answer:
Plasmodium multiplies and undergoes developmental changes inside the mosquito
Explanation:
Female Anopheles is a biological vector because Plasmodium undergoes sexual reproduction and further development within the mosquito. The parasite is not simply carried passively on the body surface.
5. During a blood meal, which event specifically enables a malaria-infected female Anopheles to transmit Plasmodium to a human?
A.
Injection of saliva containing sporozoites from the mosquito's salivary glands
B.
Regurgitation of male gametocytes from the mosquito's gut
C.
Release of ookinetes from the mosquito's Malpighian tubules
D.
Injection of oocysts formed in the mosquito's abdominal muscles
Correct Answer:
Injection of saliva containing sporozoites from the mosquito's salivary glands
Explanation:
After development in the mosquito, sporozoites migrate to the salivary glands. During probing and feeding, an infected female Anopheles injects saliva containing these sporozoites into the human host.
6. Which mosquito behavior most increases the likelihood that an infected female Anopheles will transmit malaria to humans?
A.
Repeated nocturnal blood-feeding on human hosts
B.
Exclusive feeding on floral nectar during daylight
C.
Laying eggs only in dry soil away from water
D.
Feeding exclusively on male mosquitoes during the night
Correct Answer:
Repeated nocturnal blood-feeding on human hosts
Explanation:
Female Anopheles mosquitoes are generally active and feed mainly at night. Repeated blood-feeding creates opportunities for the mosquito to acquire Plasmodium from an infected person and later inoculate sporozoites into another person.
7. Which statement best explains why targeting female Anopheles larvae can reduce malaria transmission before adult mosquitoes emerge?
A.
Larvae are aquatic stages of the mosquito and cannot transmit malaria, but eliminating them reduces the future vector population
B.
Larvae already inject sporozoites into humans while living in water
C.
Larvae are the only mosquito stage in which Plasmodium undergoes sexual reproduction
D.
Larval control prevents males from producing the blood meal required by females
Correct Answer:
Larvae are aquatic stages of the mosquito and cannot transmit malaria, but eliminating them reduces the future vector population
Explanation:
Anopheles larvae develop in water and do not bite humans or transmit malaria. Removing or treating larval habitats prevents emergence of adult females, thereby reducing the number of potential vectors.
8. A control program removes shallow collections of clean, sunlit water near houses. Which vector-related assumption does this intervention primarily exploit?
A.
Anopheles breeding sites can include suitable stagnant or slowly moving water where immature stages develop
B.
Adult female Anopheles completes its entire life cycle in dry soil
C.
Male Anopheles deposits eggs directly into human blood
D.
Sporozoites multiply only in exposed surface water before entering mosquitoes
Correct Answer:
Anopheles breeding sites can include suitable stagnant or slowly moving water where immature stages develop
Explanation:
Anopheles eggs, larvae, and pupae are associated with aquatic habitats. Eliminating suitable water collections reduces breeding and therefore lowers the abundance of adult female vectors.
9. Which observation would most strongly support identification of a captured adult mosquito as a female Anopheles rather than a male Anopheles?
A.
It has feathery antennae and feeds on plant nectar
B.
It has non-plumose antennae, palps nearly equal in length to the proboscis, and a blood-engorged abdomen
C.
It has short palps, rests parallel to the wall, and lacks piercing mouthparts
D.
It has no proboscis but possesses long hind legs adapted for swimming
Correct Answer:
It has non-plumose antennae, palps nearly equal in length to the proboscis, and a blood-engorged abdomen
Explanation:
Female Anopheles has relatively simple antennae, long palps approximately as long as the proboscis, and piercing-sucking mouthparts that permit blood-feeding. A blood-engorged abdomen further supports that identification.
10. Why does interruption of contact between humans and female Anopheles reduce malaria transmission even when Plasmodium remains present in the human population?
A.
It prevents mosquitoes from acquiring gametocytes and later depositing sporozoites during another blood meal
B.
It prevents Plasmodium from reproducing in human red blood cells by removing the mosquito's larvae
C.
It converts female mosquitoes into harmless males after a missed blood meal
D.
It destroys all Plasmodium stages directly by preventing mosquito eggs from hatching
Correct Answer:
It prevents mosquitoes from acquiring gametocytes and later depositing sporozoites during another blood meal
Explanation:
Transmission depends on blood-feeding by female Anopheles. Preventing mosquito-human contact blocks acquisition of Plasmodium from an infected person and inoculation of sporozoites into a susceptible person.
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