Nektons are

Habitat together with the functions of a species constitutes its

How can seals survive in a polar climate where the temperature prevails below $0^{\circ} C$?

$A$ regulators are able to maintain homeostasis by means which ensure constant body temperature,constant osmotic concentration,etc. All $B$ and $C$ and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).
Evolutionary biologists believe that the 'success' of mammals is largely due to their ability to maintain a constant body $D$ and thrive whether they live in Antarctica or in the Sahara desert.
Choose the correct option for $A, B, C$ and $D$.

Altitude sickness,which includes nausea,fatigue,and heart palpitations,occurs due to:

The aquatic organism that can actively swim at will against the water current is