| S. No. | Ammonotelism | Ureotelism | Uricotelism |
| (i) | Excretory waste is ammonia (NH3). | Excretory waste is urea (NH2-CO-NH2) | Excretory waste is uric acid. |
| (ii) | It is characteristic of aquatic animals such as protozoans, sponges, coelenterates, crustaceans, bony fishes and echinoderms etc. | It is characteristic of mammals, cartilaginous fishes (e.g., dogfish) and amphibians etc. | It is characteristic of terrestrial reptiles and insects. All the birds are uricotelic. |
| (iii) | Excess of water is required to eliminate ammonia. It is highly toxic. | Less water is needed, urea is less toxic than ammonia. It can be retained for some time in body without any harmful effect. | Much less water is needed. Uric acid is least toxic. |
| (iv) | Water loss is about 300-500 ml to remove one gram of ammonia. | Water loss is about 50 ml to eliminate one gram of urea. | Water loss is about 10 ml to excrete out one gram of uric acid. |
| (v) | Ammonia is formed in liver cells by the deamination of the amino acids. | Urea is formed in liver by detoxification of ammonia. | Uric acid is formed mainly from the purines in liver cells. In insects, uric acid is formed in malpighian tubules. |
