Based on the following information, answer the questions given below:

Animals adapt to the environment in different ways to cope up. An animal 'P' excretes concentrated urine to conserve water. Some plants have sunken stomata and thick cuticle. Mammals from colder climates generally have shorter ears and limbs to minimise heat loss. In the polar seas, aquatic mammals like seals have a structure Q which acts as an insulator and reduces loss of body heat. Humans experience altitude sickness at high altitudes. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of hemoglobin and by increasing breathing rate.

Question:

The structure 'Q' present in seals is made up of