20
votes
Accepted
Why do cartilaginous fishes not excrete ammonia?
This is an interesting question. Most fish are ammonotelic, meaning the excrete ammonia (which is toxic to vertebrates) through their gills, which is a very energy efficient way (reference 1 and 2).
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- 51.6k
8
votes
Why is ammonia converted to urea rather than secreted in the urine?
The comment of the poster to my request for clarification cites “The formation of ammonia itself requires… large quantities of water to dilute it out of a biological system” I conclude that he assumes ...
- 25.7k
7
votes
Why are human feces riskier than urine with regard to spreading diseases?
Many gut microbes are pathobionts or opportunistic pathogens — these organisms can be part of the normal gut flora (microbiome) of healthy individuals, but under the right (for them) circumstances (e....
- 5,598
6
votes
Why are human feces riskier than urine with regard to spreading diseases?
Urine is contaminated with skin bacteria and possibly something excreted from your blood. A very tiny fraction of urine is microbial.
Feces is basically a solid mass of undigested food, gut bacteria, ...
- 14.7k
5
votes
Accepted
Recycling and storage of nitrogen from breakdown of macromolecules?
The premise of the question is incorrect. Mammalian organisms do recycle nitrogen. They only excrete excess nitrogen.
Ammonia from deamination of amino acids can be incorporated into glutamate and ...
- 25.7k
5
votes
Recycling and storage of nitrogen from breakdown of macromolecules?
Short answer: This is because the most common form of nitrogen found in multicellular organisms (not incorporated into any other compound) i.e. ammonia is too toxic to be stored or recycled.
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- 14.1k
5
votes
Why are human feces riskier than urine with regard to spreading diseases?
The kidney is essentially a filter which extracts dissolved waste products & water from the blood. It basically allows only molecular-sized things to pass, otherwise it would continually leak ...
- 3,643
3
votes
Is there a function for urea in sweat?
Tl;DR: Urea is a metabolic waste excreted from human body. As such it does not have any function in human body. It is a major product in the waste excreted from kidneys although trace amounts can be ...
- 1,214
3
votes
Why are human feces riskier than urine with regard to spreading diseases?
I can only speak to what I am familiar with, but I would assume that the large majority of those viruses are bacteriophages. These bacteriophages, or "phages" for short, are viruses that infect ...
- 379
2
votes
Is the chemical composition of urine detrimental or beneficial for a tree?
Here is a book about dry-matter production of urine treated plants. If we consider that trees are large plants, it's fair to apply the study to trees too:
The findings of the study suggested that ...
- 10.4k
2
votes
What mammal or creature dropped this? (Warning: Gross Pictures)
You can see a similar pile of bird poop seen below a barn swallow nest:
Source: deepmuckbigrake
Alternatively, if it really did appear overnight, perhaps a pile pf pigeon poop was pushed out of a ...
- 29.9k
1
vote
Accepted
Does poop have protein?
Human stool, on average is about 25% solids and 75% water. Up to 54% of the dried solids consist of bacterial biomass, of which protein comprises up to 50% (1). This is pretty consistent with other ...
- 4,714
1
vote
Is the chemical composition of urine detrimental or beneficial for a tree?
Speaking specifically about blueberry bushes as a perhaps extreme example, they thrive in acidic soil and nitrogen-laden soil. However, dog urine is bad for blueberries, as the high nitrogen content ...
- 5,580
1
vote
Does cow urine have medicinal properties?
Interesting question anomdsgf. There are substances present in Bos taurus urine that promote antimicrobial activity. Studies like this and this have shown how the urine can inhibit the growth of ...
- 277
1
vote
Shape of feces in herbivores
I don't think it is an adaption, but the that diet plays a dominant role. The feces of cows in intensively fertilized agricultural fields, with grasses rich in protein, has no shape at all. See ...
- 3,685
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