CBSE Class 12 Biology Solved Question Paper 2012

Short Answer Type

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Trace the life-cycle of malarial parasite in the human body when bitten by an infected female Anopheles. 

Plasmodium (malarial parasite) requires two hosts – human and mosquitoes to complete its life cycle. Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs leads to release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days. When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. The parasites multiply within the mosquito’s body to form sporozoites that are stored in their salivary glands. When these mosquitoes bite a human, the sporozoites are introduced into his/her body, thereby initiating the another cycle.
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