Most marine animals are osmoconformers and keep their bodies ______to the environment, whereas most freshwater animals are osmoregulatory and keep their bodies ___to the environment.

The organisms that keep their internal fluids isotonic to their environment by maintaining an internal salinity similar to their ambient conditions are called:

Nitrogenous wastes tend to form toxic ammonia, which must be converted into a less toxic form before being eliminated from the body. Reptiles and birds convert ammonia to _________, while mammals convert it to ________.