Question

What are ammonotelic and ureotelic animals? Give examples.

Answer 1

Hint: The word ammonotelic is derived from the word ammonia and the word ureotelic is derived from the word urea. These are the two types of nitrogenous excretory wastes in aquatic and terrestrial organisms.

Complete answer:
Ammonotelic animals: These are those animals whose main nitrogenous excretory waste is ammonia. This type of excretion is called ammonotelism. Ammonotelic excretion is found in many aquatic animal groups like protozoans e.g., Amoeba, Paramecium; sponges e.g., Scypha; coelenterates e.g., Hydra; crustaceans e.g. Palaemon; echinoderms e.g. Asterias; bony fishes e.g., Teleosts; tadpole larvae and some adult aquatic amphibians e.g., salamanders.
Ureotelic animals: These are those animals whose main nitrogenous excretory waste is urea. This type of excretion is called ureotelism. It is generally found inland animals which can lose a large amount of water without any ill effects (e.g., frog, which can lose water equal to one- third of the body weight in a day); and those which can retain a considerable amount of urea as a major osmotyle (solute) to maintain osmolarity (number of solutes per liter) of their blood and other body fluids e.g., elasmobranchs.

Additional Information:
- Ammonia is the basic nitrogenous catabolic product of protein and is produced in all body tissues of vertebrates.
- In the liver of the vertebrate, excess of amino acids is converted into ammonia by the help of enzyme oxidase.
- One gram of urea needs about 50 ml of water to be expelled out of the human body.

Note: Ureotelism is the common method of excretion in man and all other mammals, even aquatic mammals like whales and seals; and desert mammals like camels, kangaroo rats; terrestrial and semi- aquatic amphibians like a frog. In man, urea accounts for 80-90% of total nitrogenous waste products.