[ConfusedHermit (OP)]

What are some animals whose bodies aren’t made up mostly of water (or at all), and why are they able to survive whereas we need our body’s water?

In fact, why is water so to most organisms? Did it just happen to end up being the element that supports life the most on this planet? Could we have ended up with any other element were our planet any different?

I’ve also wondered this about iron. Why is something that grows from the Earth in our bodies and doing things with our blood?

So that’s… 2, 3… 5 Questions. I need to work on that… :{o~


_{Mod edit - formatted the subject as a question.  Please do this in future to help keep the forum tidy and easy to navigate.  Thanks!}

[CliffordK]

ALL cells on Earth require water. 

In many senses, cells are somewhat like detergent micelles, with lipid bilayer encapsulating an aqueous solution of all the cellular machinery.

This is one of the reasons that oil can be a reasonably good preservative, and that one can store a bottle of cooking oil without refrigeration.

Some organisms have different methods of conserving water.  In particular, multicellular organisms must maintain salt and nitrogen balance, usually done in the kidneys.  Some desert lizards can concentrate urine so much that they can essentially pass solid urine.

[ConfusedHermit (OP)]

Okay :{o~

So, about the prevalence of water, iron, and other things in organisms...

I was wondering about it earlier. Is the reason organisms have so many things that are present in nature (such as water and iron) simply because the planet does, so THEY need to have those things in them to survive here?

Would life have other chemicals in them if the planet was made up of a majority of different chemicals?

[CliffordK]

Undoubtedly some of the elements and compounds are used because of their prevalence in nature, and access on earth.  If you look at the periodic table, to a large extent stuff in columns behave similarly.  So, silicon might substitute to some extent for carbon, and sulfur for oxygen.  But, the elements and compounds such as carbon and water also have unique properties that make life possible.  We really can't answer whether life is possible without them.

An study last year suggested an organism that can substitute arsenic for phosphorous.  Also, Follow links for full text.  However, apparently those findings are controversial.  Also see footnotes under first link.  Perhaps they can substitute some of the phosphorous (as in DNA), but not all of it (as in ATP).

Iron is an example of an element that has a very specific function in higher organisms.  It is a critical component in blood for its ability to reversibly bind oxygen.  While oxygen does dissolve in water, the hemoglobin increases the oxygen carrying capacity of the blood.

Did Spock have blue-green blood?  Some crabs actually use hemocyanin based on copper rather than iron for the transport of oxygen.  And, thus they have blue blood.

If a planet was iron poor, other elements such as copper might be chosen for a similar functionality.

Perhaps there would be completely different substitutes for intracellular energy with ADP/ATP (other than the potential arsenic mentioned above).

One might note that the terrestrial life has very specific amino acids and other complex molecules used as fundamental building blocks for many other biologic molecules.  Some molecules have multiple potential configurations with the same formula called chirality.  Terrestrial life typically only uses a single chiral form of each compound.  Perhaps "alien" life would sellect different chiral isomers.  And, at least some of the amino acids would be different.

[ConfusedHermit (OP)]

That bit about crabs is awesome! Blue blood, just from copper instead of iron.

That actually gives good reason to science fiction depictions of aliens with an odd colored blood instead of just 'because it looks cool.'

Thanks once again, great info ;{D~