Terror of Bengal-CBSE 12 BIOLOGY

1. Eichhornia crassipes : These plants which were introduced into India for their lovely flowers have caused havoc by their excessive growth by causing blocks in our waterways. They grow faster than our ability to remove them. These are plants of water hyacinth (Eichhornia crassipes), the world’s most problematic aquatic weed, also called ‘Terror of Bengal’. They grow abundantly in eutrophic water bodies, and lead to an imbalance in the ecosystem dynamics of the water body.

Electrostatic precipitator- CBSE 12 BIOLOGY

1. Electrostatic precipitator:  To remove  particulate matter; the most widely used of which is the electrostatic precipitator which can remove over 99 per cent particulate matter present in the exhaust from a thermal power plant. It has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons. These electrons attach to dust particles giving them a net negative charge. The collecting plates are grounded and attract the charged dust particles.  The velocity of air between the plates must be low enough to allow the dust to fall.

Q. How does an electrostatic precipitator work to remove particulate pollutants released from the thermal power plants?

Catalytic converters-NCERT 12 BIOLOGY

1. Catalytic converters: Catalytic converters, having expensive metals namely platinum-palladium and rhodium as the catalysts, are fitted into automobiles for reducing emission of poisonous gases. As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas, respectively. Motor vehicles equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.
   
   Q. Why is the use of unleaded petrol recommended for motor vehicles equipped with catalytic convertors? 
   Q. Why are catalytic convertors recommended for vehicles? 
   
   

HIBERNATION, AESTIVATION AND DIAPAUSE-NCERT 12

HIBERNATION- (BEARS) - is a time when animals ‘sleep’ through cold weather. It is but one of many forms of metabolic suppression

AESTIVATION(SNAILS AND FISHES) - hibernation during summer.

DIAPAUSE(ZOOPLANKTONS)-is a stage of suspended development. When referencing animal dormancy, is the delay in development in response to regularly and recurring periods of adverse environmental conditions.

1. Bear hibernates whereas some species of zooplanktons enter diapause to avoid stressful external conditions. How are these two ways different from each other?

THERMOREGULATION IN SHREWS AND HUMMING BIRDS_ NCERT BIOLOGY 12

Conformers: Heat loss or heat gain is a function of surface area. These small animals have a large surface area relative to their volume. They tend to lose body heat very fast when it is cold outside. Then they have to expend much energy to generate body heat through metabolism. This is the main reason why they are rarerly found in polar regions.

1. Why is the polar region not a suitable habitat for tiny humming birds?
2. Humming brids live among the bushes in tropics while penguins live on icebergs. They cannot survive if their habitats are reversed. Justify