Read Malaria by Host and Parasite Stage
Follow Plasmodium across two hosts. The key changes are the infective stage, the blood-cell stage and where sexual reproduction occurs.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Follow infection in humans
An infected female Anopheles injects sporozoites. They first multiply in liver cells, then infect red blood cells. Rupture of infected red cells releases merozoites and haemozoin and is associated with recurring chills and fever.
Move the sexual cycle to the mosquito
Some parasites in human red cells become gametocytes. When a mosquito takes a blood meal, these stages form male and female gametes in the mosquito gut; fertilisation and later development occur there. The mosquito is the definitive host for the sexual phase.
Use the source wording carefully
A mosquito must be infected and allow parasite development before it can transmit sporozoites. A newly moulted adult is not infective simply because it has emerged; the decisive clue is whether it carries mature parasites.
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- ✓Human infective stage: sporozoite.
- ✓First multiplication: liver; then red blood cells.
- ✓Gametocytes develop in human blood; sexual reproduction occurs in mosquito gut.
- ✓Only an infected, parasite-bearing female Anopheles transmits malaria.
Do not place gamete formation and fertilisation inside human red cells just because gametocytes are found there.
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