How will you explain following statement with the help of the anomalous behaviour of water?
In regions with cold climate, the aquatic plants and animals can survive even when the atmospheric temperature goes below `0^@C`

Explanation

i. In cold climate, temperature of water in ponds and lakes starts falling.
ii. On getting colder, water contracts. As a result, density of water increases and it goes down. To replace it, warmer water from below rises up. This process continues till temperature of water at the bottom of pond becomes `4^(@)C`.
iii. Water, due to its anomalous behaviour possesses maximum density at `4^(@)C`
iv. If the temperature lowers further, ice is formed at the surface of pond with water below it.
v. Ice being poor conductor of heat blocks the further heat exchange between atmosphere and water in the pond.
vi. This maintains temperature of water below surface of ponds or lakes at `4^(@)C` enabling survival of aquatic plants and animals.