Mammals and birds uses evaporative cooling due to their high body temperature because this evaporative cooling removes the high temperature from the body. In this process, the water present in the body absorb all the extra heat and remove this extra heat from the body with change its state from liquid to vapors and the body's temperature cools down. This evaporative cooling is occurs in the process of sweating.
Nonsense mutations make stop codons. If the mutation is towards the beginning of a gene, then the protein that gets created will be cut short and not function properly. But if it was towards the end, there is still a chance that the protein will still be able to work.
