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I know that ammonia is toxic for the body since it disturbs enzymes of mitochondria. I want to know that why the ammonotelic animals don't get affected by it? I mean that even if there is plenty of water to remove ammonia from their body, does ammonia not cause any damage till it's inside body? Does toxicity depends on concentration level? Can anyone tell me its evolutionary significance?

Sorry for the previous question. . Actually it was a easy one and I got the answer. Sorry for the unclarity.;)

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  • $\begingroup$ I read it . It was like this-"uric acid being less toxic,can be removed with a minimum loss of water". Another one-"Terrestrial adaptations necessitated the production of lesser toxic nitrogenous wastes like urea and uric acid for conservation of water". Am I interpreting it wrong or is there some relation between them? $\endgroup$ – anamika Singh Jan 24 '15 at 6:44
  • $\begingroup$ I read it in our high school book. I want to know that' is there a evolutionary significance of it.'... I mean isn't it a coincident at the same time, a less toxic and less soluble substance is formed? I want to know how are they toxic to our body and can this TOXICITY be related to LESS NEED OF WATER FOR EXCRETION? Can there be any structural significance of these compounds in their toxicity? $\endgroup$ – anamika Singh Jan 24 '15 at 7:02
  • $\begingroup$ Toxicity does depend on concentration levels. If you want to know the evolutionary significance, add it to your question. And add the evolution tag to the question so that it gets attention $\endgroup$ – One Face Jan 30 '15 at 4:44
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The article at linked at the bottom says that the marine organisms keep the concentration of Ammonia under very strict control.

  1. pH of the ECF (Extra Cellular Fluid) is said to play a very important role.
  2. The concentration of ammonia in the environment (ambient ammonia levels) also plays an important role.
  3. Less importantly temperature also plays a role.
  4. Ionic strength of water also is involved.

The NH3:NH4+ ratio seems to be more important than the abosolute value of ammonia.


Ammonia is more toxic than ammonium ion. The lipophilic (ammonia is amphiphilic - soluble in both water and lipid) nature of ammonia allows it to easily cross the cell membrane and the blood brain barrier (in organisms where BBB exist) and affect the physiologic functions. The ammonium ion on the other hand can't enter the cell as easily, as it is not as soluble in lipid as ammonia.


  1. For ammonia and marine organisms see http://www.sciencedirect.com/science/article/pii/S1546509801200053
  2. For more on ammonium toxicity see: http://www.ucl.ac.uk/~ucbcdab/urea/amtox.htm

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