 Dear students, in this topic we shall discuss the excretion of Ammonia and Ammonotelic animals. The animals which excrete Ammonia as their major nitrogenous waste are called Ammonotelic animals. They include most tilioste fishes and aquatic invertebrates. These animals have a plenty of water available for the removal of Ammonia. So they produce little or no urea. Dear students, now we shall discuss the mechanism of formation of Ammonia. The deamination of amino acids in the cells removes amino group NH2 group. And transaminase enzyme transfers the amino group to the amino acid glutamate. In the liver, glutamate is deaminated to form Ammonia mines and alpha keto glutamate. In Ammonotelic animals and fishes, they dissolve in the plasma water to form Ammonia. And Ammonia is excreted through gills or kidneys. In mammals and urea excreting animals, Ammonium ions are converted into urea by urea cycle in the liver. The liver also converts the glutamate to glutamine which is much less toxic than Ammonia. Glutamine is released from the liver into the blood and acts as an amino group carrier through the blood and tissues until it reaches the kidneys. In the kidneys, tubular cells deaminate this glutamine, liberating Ammonia into the tubular filtrate. In the tubular filtrate or tubular fluid, Ammonia takes up a proton to form the Ammonium ions. Ammonium ions, once in tubular fluid, they cannot diffuse back. So they leave the body through urea. Dear students, now we shall discuss the excretion of Ammonia through gills or fishes. Most of Ammonia in fishes is excreted across the gill surfaces. The gill membranes are highly permeable to Ammonia, so they permit its passive diffusion. Due to this, carbon dioxide is also removed from the gills, and hydrogen ions are also removed. The result is that the water of the gill surface is acedified. The acedified water that traps Ammonia, so it enhances Ammonia excretion. Dear students, now we shall discuss about the toxicity of Ammonia. A blood concentration of only 0.05 millimole per litre of Ammonia is toxic to most animals. Ammonia toxicity causes convulsions, coma, and death. Ammonia is toxic because it alleviates the pH, causing protein denaturation. It interferes with ion transport mechanisms. It also affects blood flow in the brain and also affects synaptic transmission.