Question

In birds, urinary bladder is present in
A. Parrot
B. Ostrich
C. American Rhea
D. Both B and C

Answer 1

Hint: Birds have kidneys that are involved in the removal of nitrogen. The birds do not have urethra/ urinary bladder. They convert nitrogen into uric acid, which is then expelled along with the faeces.

Complete answer: Urine is a liquid by-product that is formed by filtering wastes and water from the blood in many vertebrates.
Birds convert nitrogen into uric acid as it reduces water wastage.
 Uric acid is less toxic and need not be diluted much.
Birds conserve body water by producing urine that is osmotically concentrated. The concentrating of the urine occurs in the medullary cone of the nephron. The medulla consists of high concentrations of solutes. Therefore when urine that is formed in the bird’s body passes through it, water leaves it via osmosis, concentrating it more.
The ostrich and American rhea secrete urine separate from faeces. The urine is stored in the coprodeum whereas the faeces is stored separately in the terminal colon.
The coprodeum and the cloaca are majorly involved in osmoregulation.
The ostrich has a urinary bladder in the form of a dilated pouch of ureter that stores the urine as it is secreted. The American rhea stores the urine in an expansion of the cloaca.
So, in birds the urinary bladder is present in Ostrich and American Rhea.
Therefore the correct answer is (D) Both B and C.

Note: The removal of water in the form of water causes dehydration. Therefore, the pituitary gland of the bird produces a hormone known as Arginine vasotocin into the blood. This reduces the glomerular filtration rate, thereby decreasing the amount of water that moves from the blood into the kidney. It also increases the permeability of the walls of the ducts by opening aquaporins, thereby increasing reabsorption of water.