Final answer:
Urea and uric acid are waste products of nitrogenous compounds; urea is formed efficiently in the liver, is more water soluble, and is excreted by mammals in urine, while uric acid, which is less soluble, is excreted primarily by birds, reptiles, and insects in feces to conserve water.
Step-by-step explanation:
Comparison of Urea and Uric Acid Formation
Both urea and uric acid are waste products formed from the breakdown of nitrogenous compounds in the body. Urea is produced in the liver through the urea cycle, which converts toxic ammonia into urea, a less toxic compound. This process is more energy-efficient and less complex than the formation of uric acid. Urea is more soluble in water than uric acid, which allows it to be easily excreted in urine by mammals, including humans. On the other hand, uric acid is formed primarily in birds, reptiles, and insects through a uric acid cycle, which also starts with ammonia. Uric acid is less soluble in water, leading to its excretion as a semi-solid paste with minimal water loss, primarily through feces, which is advantageous for conserving water in arid environments. This excretion method evolved as a means to minimize water loss in organisms living in dry conditions.