In a strictly biological sense, what exactly does “organic” mean? And does life have to be organic?
Organic means carbon based. There aren’t any non carbon based life-forms.
On Earth. They may very well exist elsewhere.
I think you will find that “organic,” originally meaning something that is a living thing with organs (cf: organism), has come to mean carbon-based living stuff, since all life as we know it is carbon-based. I am not aware of any life forms on earth, even the weirder bacteria, that are not made-up of carbon in combination with something else.
I know that some assert that “organic” life also is based upon water as a solvent. I’m not sure how critical that is to the definition, that is, whether or not one could consider life that is carbon based, but which, for example, uses ammonium as a solvent “organic.”
Having never found any life that is not “organic” in this sense, it is hard to say whether or not life based on some other elements could be found.
Also, Frank Edwards documented a “scientist’s” synthesis of silicon-based life in one of his “Strange” books.
Well, now, that’s pure speculation. There are some significant difficulties with non-carbon, non-water life forms. I suppose it depends upon whether you prefer to rule out what you don’t know exists, or rule in what you can’t disprove. 
Let’s explain the history of the word “organic” in regards to chemistry. At first, chemists knew there were certain substances that were produced by living things, these chemical substances were called “organic”. And other substances were produced by non-living process, these were called inorganic. But they didn’t have a clear understanding of what made them different. But there was an idea that there was some sort of vital essence to living things that somehow made them different from nonliving things.
Then someone figured out a way to synthesize urea, an organic compound, from inorganic chemicals. And so chemists learned that there was no principled difference between organic and inorganic chemistry, but still the chemicals called “organic” had some pretty unusual properties compared to inorganic chemicals. As our understanding of how and why that was increased, it was realized that organic chemicals invariably contained carbon atoms, and eventually we figured out that carbon had the property of being able to form four chemical bonds which allowed a near infinite complexity of compounds to be formed.
So nowadays we still retain the name “organic” but it refers to compounds that contain carbon rather than compounds derived from living things. Of course, some carbon containing compounds are deemed inorganic, like CO2 or CaCO3, because the chemistry of these compounds is more similar to other inorganic compounds. But there’s no principled distinction why CO2 should be inorganic while CH4 should be organic, it’s just a useful way of thinking about chemistry.
Dang, after typing all that, I should have just cited: Organic chemistry - Wikipedia
Oh, and while we can theorize about non-carbon based life, elements other than carbon have some pretty severe differences that make them unlikely candidates. There are some compounds where silicon replaces carbon in analgous ways, but silicon just doesn’t form nearly as many complext molecules like carbon does.
Organic chemistry is specifically the chemistry of carbon compounds (regardless of whether or not they originate from living organisms).
By this definition, all life on Earth, and all known life, is organic.
Life based on elements other than carbon, particularly silicon, is speculatively possible. (I won’t say theoretically, since we don’t know enough about it to know if it is theoretically possible.)
The relevant part of the definition from Merriam-Webster:
Another part of the definition, however, is:
If life based on other elements were discovered, one might say it was organic in this sense. However, the de facto definition at present is that organic means carbon-based.
For more on silicon, see this article:
Damn, I love wikipedia.
Guys, I might point out he said, “in the strictly biological sense…” A discussion of organic chemistry is a bit off point, n’est-ce pas?
Scientists have to be very careful when they are writing the criteria for life because it is easy for fire to slip in there. Sometimes they use some type of carbon-based criteria but this question asks something different. I vote that fire is alive and that is one reason I like it so much.
A discussion of organic chemistry is extremely relevant to the biology of life. Biology can’t be fully understood without chemistry. How else are you going to explain the lipid bilayer of the cell wall without first understanding things like polarity?
As far as I know, the “whorish” nature of carbon (will bond so easily with any number of partners with varying levels of attractiveness) is one of the essential elements of life. Now, there could be life that doesn’t depend on this microscopic level of diversity, but carbon makes a lot of things possible. Proteins are formed by weird shapes of organic molecules. There’s so many freaking combinations possible, they are like atomic lego blocks. Carbon, the most promiscuous of them all makes it possible. It’s the universal connecting piece.
Sulfur makes Carbon look like a Virgin.
I dunno, sulfur may be more promiscuous, but carbon is a lot more adventuresome. You won’t see sulfur getting into the same sort of many-atom orgies that carbon is so fond of.
The thing with carbon is, other atoms can form long chains, and other atoms can form complicated structures, but no other atom can do both as well as carbon. I could envision protein-equivalents, for instance, built around an asbestos-like backbone, with active sites made of nitrogen, sulfur, and phosphorus hanging off of it, but it’d be a lot more complicated than making both the backbone and the active sites out of carbon.
I’ve got a transition metal brothel in my hood. 