Subject

Biology

Class

ICSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsLong Answer Type

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51. Explain the development of an anther and the formation of microspores in angiosperms.


As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. As each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad. Each one is a potential pollen or microspore mother cell (PMC). The process of formation of microspores from a pollen mother cell through meiosis is called microsporogenesis. The microspores, as
they are formed, are arranged in a cluster of four cells–the microspore
tetrad. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther. 



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52.

State four causes and four consequences of population explosion.

 

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53. What are the important changes in the evolution of the modern horse from the Eohippus (ancestral horse) ?   
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