Enantiostasis (1 Viewer)

[Calculon]

In the macquarie revision guide it reads as follows:
"[Marine fish excrete] Small quantities of concentrated urine, usually composed of trimethylamine oxide, other wastes and small volumes of water".
In fact the only marine fish that I could find which doesn't excrete trimethylamine oxide is the shark, and that excretes urea. I did a Ctrl+F search through the entire biology syllabus and it does not mention ammonia at all in the entire document. Why? Because the syllabus is full of questions, not answers.

 

[xiao1985]

lolz true true...

cal is true on that... lolz...
infact, syllabus is alot vague on what you should study... but the questions that need to be answered... regarding how precise you wish to answer the question, you the sole stakeholder... you can answer it as precise as possible and hope the marker is a smartie, who uses macq guide and/or who knows about trimethylamine oxide, or you can write what ever appear in your text book and hope your marker doesn't know it...

for as far as the marker is concerned, if it is not on the text book, it's not right... they log on to internet and do a 10 min search on if salt water fish do actually excrete nitrogenous waste as trimethylamine oxide...

but if i'd do the question, i'd shove the technical stuff in... cuz a) it looks good, and b) it is right and c) it does appear in text books...

 

[Survivor39]

Alright alright!

I just looked up my first year biology text book. Freshwater fish excrete Ammonia, while marine (salt water) fish excrete urea.

Fresh water fish takes in Na+ ions from the water in exchange for NH4+.
Marine species (including fish) simply do not have access to enough water to excrete ammonia. So urea is excreted.

 

[Survivor39]

But then again, you don't really have to be that specific in answering the question. The markers really want you to know the importance of enantiostasis, not what individual species excrete.

They are not going to ask you to name the compound that marine fish excrete.

 

[04er]

so does everyone agree with survivor?

 

[TheKing]

well what survivor says is totally contradictory to wjat calculon says...