AP BIOLOGY

Detailed explanation-1: -1 gm of urea needs about 50 ml of water to the expelled out. It is commonly found in man, whales, seals, desert mammals like kangaroo rats, camels, toads, frogs, cartilagenous fishes, aquatic and semi aquatic reptiles like alligator, terrapins and turtles.

Detailed explanation-2: -Uric acid is also less toxic than ammonia or urea. It contains four nitrogen atoms; only a small amount of water is needed for its excretion.

Detailed explanation-3: -A lot of water is needed for the excretion of ammonia, about 0.5 L of water is needed per 1 g of nitrogen to maintain ammonia levels in the excretory fluid below the level in body fluids to prevent toxicity.

Detailed explanation-4: -1 gram of ammonia requires 300-500ml of water therefore 2g of ammonia will require 600-1000 ml of water. So, for 2g ammonia removal, 1000 ml water is required.

Detailed explanation-5: -Urea is less toxic and requires less water to remove from organism (so it’s better in terrestrial environment) but it requires more energy to produce.