Question

Which one of the following animals is uricotelic?
a. Lizard
b. Camel
c. Toad
d. Rohu fish

Answer 1

Hint: Uricotelic mode of excretion involves minimum loss of water.

Complete answer:
Animals living in dry conditions adopt the Uricotelic mode of excretion. Uricotelic animals excrete uric acid crystals from ammonia as their excretory product. Example: birds, land snakes, lizards, etc. Due to dry conditions, these animals conserve water in their bodies. Uric acid crystals can be retained in the body (in solid form) for a considerable time before being discharged from the body.

Additional information:
Animals have been broadly classified into three modes of excretion:
Ammonotelic animals: Animals that excrete ammonia as their waste are called ammonotelic animals. Ammonia is highly poisonous and water-soluble and is produced by quick diffusion of water. Examples: The majority of marine animals namely cnidarians, echinoderms, fishes, protozoans, larvae/tadpoles of amphibians, crustaceans, poriferans, and platyhelminths are ammonotelic.
1. Ureotelic animals – Animals that excrete urea in the form of waste are called ureotelic animals. Urea is less harmful than ammonia and requires less water for excretion. Examples: Few bony fishes, adult amphibians, fish, cartilaginous fish, and mammals including humans are ureotelic.
2. Uricotelic animals – Animals that excrete uric acid in the form of waste are called uricotelic organisms. Uric acid is the least poisonous and the least soluble in water, relative to ammonia and urea. Examples: Birds, snakes, and lizards are uricotelic.

So, the correct answer is (a) ‘Lizard’.

Note: Ammonia, urea, and uric acid are the major forms of nitrogenous wastes excreted by the animals, ammonia being the most toxic. The common excretory products are ammonia, carbon dioxide, urea, uric acid, guanine, and creatine.