[Campbell Biology P.1032] In birds and reptiles, the production of uric acid as a primary nit... | Practice Question

In birds and reptiles, the production of uric acid as a primary nitrogenous waste product provides a selective advantage, particularly concerning their shelled eggs. Which of the following best explains this advantage?

  • A: Uric acid is highly soluble, allowing easy diffusion out of the eggshell into the external environment.
  • B: Uric acid is less toxic than ammonia or urea, and its insoluble nature allows it to be stored as a harmless solid within the egg.
  • C: The synthesis of uric acid requires less energy, making it an efficient waste product for the energy-intensive process of embryo development.
  • D: Uric acid can be readily reabsorbed by the developing embryo, conserving nitrogen within the egg.

Explanation

Bird and reptile eggs are surrounded by a shell that is permeable to gases but not liquids. If soluble nitrogenous wastes like ammonia or urea were produced, they would be trapped within the egg and accumulate to dangerous levels. Uric acid's relatively low toxicity and its ability to be stored as a harmless, insoluble solid semisolid paste within the egg prevent such accumulation, providing a crucial selective advantage for terrestrial reproduction.