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Modes of Excretion: Ammonotelism, Ureotelism, and Uricotelism

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Estimated time: 5 minutes
CBSE: Class 12
Maharashtra State Board: Class 12

Key Points: Modes of Excretion: Ammonotelism, Ureotelism, and Uricotelism

Feature Ammonotelism Ureotelism Uricotelism
Waste excreted Ammonia Urea Uric acid
Water needed Large amount Moderate amount Very less amount
How excreted Diffusion across body surface as NH₄⁺ ions Through kidneys As pellets/paste, minimum water loss
Toxicity Most toxic Less toxic than ammonia Non-toxic, almost insoluble in water
Conversion Direct Ammonia converted to urea via ornithine/urea cycle (3 ATP used) Ammonia converted to uric acid via inosinic acid pathway (in liver of birds)
Examples Aquatic invertebrates, bony fishes, aquatic amphibians, aquatic insects Mammals, cartilaginous sharks, rays, aquatic reptiles, most adult amphibians, terrestrial animals, marine fishes Birds, reptiles, land snails, insects
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