Why are coral reefs not found in the regions from West Bengal to Andhra Pradesh but are found in Tamil Nadu and on the east coast of India?
Coral reefs are found in zone with high salt concentration (salinity), optimal temperature and with a less siltation condition which fairly facilitate to colonise corals. In case of high siltation and water flow, coral reef do not colonise.
If a freshwater fish is placed in an aquarium containing sea water, will the fish be able to survive? Explain giving reasons.
No, a freshwater fish placed in the aquarium containing sea water, will not be able to survive. Because, its body system is adapted to function normally in a narrow range of salinity and it cannot survive in the high salinity of sea water.
Why do all the freshwater organisms have contractile vacuoles whereas majority of marine organisms lack them?
Contractile vacuole helps in osmoregulation. Because of the cellular environment of a freshwater organism being hypertonic, the water diffuses inside the cell constantly and gets collected in the contractile vacuole, which squeezes the extra water out of the cell periodically.
Thus, keeping the internal environment constant. While in case of marine organisms, this does not occur due to high salinity, therefore no need of contractile vacuole.
Define heliophytes and sciophytes. Name a plant from your locality that is either heliophyte or sciophyte.
Plants growing well in bright sunlight or favour bright light are called heliophytes or sun plants. While those plants which require low intensity of light or partial shade for growing are termed as shade loving plants or sciophytes.
Why do submerged plants receive weaker illumination than exposed floating plants in a lake?
Submerged plants receive weaker illumination than exposed floating plants in a lake because all colours of the visible components of the spectrum of light do not enter or penetrate in the depths of water.