Biology / Unit 13 Bio 3245 short lesson, about 20 seconds
Nitrogenous Waste Forms and Tradeoffs
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The idea
Animals excrete nitrogenous waste as ammonia, cheap to produce but toxic and needing dilution; urea, less toxic and soluble; or uric acid, non-toxic and insoluble but costly to make.
In practice
Aquatic animals often excrete ammonia directly; birds and reptiles excrete uric acid to conserve water.
Where people slip
No waste form is universally best — each trades production cost against water conservation, matching habitat.
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