The advantage of excreting nitrogenous wastes as urea instead of ammonia is that: a) urea requires more water for excretion than ammonia b) urea is less toxic than ammonia c) urea can be exchanged for na+ d) urea requires less energy to produce than ammonia

Describe the change in phase and temperature as water moves from the oceans to the atmosphere and then returns to earth again as rain. a) evaporation : temperature increases; condensation : temperature decreases; precipitation (rain) : temperature decreases b) evaporation : temperature increases; condensation : temperature decreases; precipitation (rain) : temperature increases c) evaporation : temperature decreases; condensation : temperature decreases; precipitation (rain) : temperature decreases d) evaporation : temperature increases; condensation : temperature increases; precipitation (rain) : temperature decreases