Question

Mammals are ureotelic, but birds are obliged to be uricotelic. Explain.

Answer 1

Mammals usually get an adequate amount of water. Hence, they can use water for excretion of urea with loss of water in the form of urine. Also, the presence of urinary bladder helps in storage of urine until it is discharged. Birds are obligate uricotelic as water is not easily available in the excess. The urinary bladder is absent in birds and ureter opens in cloaca directly. The body of birds must be kept the light for flight as the presence of water will be disadvantages for them. Thus they are uricotelic as urea needs more amount of water to dissolve.