Q5 of 42 Page 1

Name the pollutant attributed to be the cause of ‘ozone-hole’ over the Antarctica region.

OR


List the greenhouse gases other than carbon dioxide.


Chlorofluorocarbons (CFCs) is the pollutant that is the cause of ‘ozone – hole’

Polar stratospheric cloud (also called nacreous clouds) provide the surface which involves the chemical reactions responsible in ozone destruction , this reaction lead to the production of free chlorine and bromine (released from CFCs) which directly destroy ozone molecules.



OR


The greenhouse gases are (other than CO2 ) -


1. Water vapor (O)


2. Methane (C)


3. Nitrous oxide (N2O)


4. Ozone (O3 )


5. Chlorofluorocarbons (CFCs)


6. Hydrofluorocarbons (includes HCFCs and HFCs)


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3

What is ‘Saltation’ according to de Vries?

 4

Write the scientific name of the organism Alexander Fleming worked on and discovered the first antibiotic. Was the organism he worked on a fungus or a bacterium?

OR


Suggest a method to overcome excessive inbreeding depression.


 6

(a) List any two characteristic features of wheat flowers that make it a good example of wind pollination.

(b) It is observed that plant breeders carrying out wheat hybridization often take pollen grains from the ‘pollen banks’. Do you agree? Give one reason in support of your answer.


 7

Differentiate between Turner’s syndrome and Down’s syndrome.