Q13 of 43 Page 1

When and where do tapetum and synergids develop in flowering plants? Mention their functions.

OR


Where are the following structures present in a male gametophyte of an angiosperm? Mention the function of each one of them.


(a) Germ pore


(b) Sporopollenin


(c) Generative cell


• Tapetum: It develops during microsporogensis in the anther (microsporangium.) Its function is to provide nourishment to the developing pollen grains.


• Synergids: They develop during megasporogenesis in the ovule (megasporangium.) Synergids have the filiform apparatus which help to guide the pollen tube into it.


OR


a) Germ pore: It is present it the exine of the pollen grain. Its function is that it serves as a site for the emergence of the pollen tube.


b) Sporopollenin: It is found in the exine of pollen grains. Its function is to protect the pollen grain from extremes of temperature and against strong acid and alkalis.


c) Generative cell: It is found in the pollen grain. Its function is that it gives rise to two male gametes.


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11

A corn farmer has perennial problem of corn-borer infestation in his crop. Being environmentally conscious he does not want to spray insecticides. Suggest solution based on your knowledge of biotechnology. Write the steps to be carried out to achieve it.

 12

State ‘two’ observations made by German naturalist, Alexender von Humboldt during his extensive explorations in South American jungles.

OR


If in a population of size ‘N’ the birth rate is represented as ‘b’ and the death rate as ‘d’, the increase or decrease in ‘N’ during a unit time period ‘t’ will be:



The equation given above can also be represented as:



What does ‘r’ represent? Write any one significance of calculating ‘r’ for any population.


 14

Construct a flow chart exhibiting sequential events of oogenesis.

 15

Draw L.S. of an embryo of grass and label its parts.

OR


Draw a diagrammatic sectional view of a seminiferous tubule (enlarged) in humans and label its parts.