- We do not expect increasing entropy a priori, because Second Law is true only in closed systems. Open systems in general case have arbitrary entropy production. Under some nice conditions, Prigogine's theorem shows that in open systems entropy production is minimal. And the Earth, thanks to the Sun, is open system.
Entropy production is not the same as entropy, though. I think entropy production can be minimized by maximizing local entropy, since then there's no more space for entropy? I.e. since most of the CO2 has been broken up into carbon, there's not m...
I think one shouldn't think of entropy as fundamentally preferred or fundamentally associated with a particular process. Note that it isn't even a well-defined parameter unless you posit some macrostate information and define entropy as a property of a system + the information we have about it.
In particular, life can either increase or decrease appropriate local measurements of entropy. We can burn the hydrocarbons or decay the uranium to increase entropy or we can locally decrease entropy by changing reflectivity properties of earth's atmosphere, etc.
The more fundamental statement, as jessicata explains, is that life uses engines. Engines are trying to locally produce energy that does work rather than just heat, i.e., that has lower entropy compared to what one would expect from a black body. This means that they have to use free energy, which corresponds tapping into aspects of the surrounding environment where entropy has not yet been maximized (i.e., which are fundamentally thermodynamic rather than thermostatic), and they also have to generate work which is not just heat (i.e., they can't just locally maximize the entropy). Life on earth mostly does this by using the fact that solar radiation is much higher-frequency than black-body radiation associated to temperatures on Earth, thus contains free energy (that can be released by breaking it down).
Maybe I'll add two addenda:
It's easy to confuse entropy with free energy. Since energy is conserved, globally the two measure the same thing. But locally, the two decouple, and free energy is the more relevant parameter here. Living processes often need to use extra free energy to prevent the work they are interested in doing from getting converted into heat (e.g. when moving we're constantly fighting friction); in this way we're in some sense locally increasing free energy.
I think a reasonable (though imperfect) analogy here is with potential energy
The amount of entropy in a given organism stays about the same, though I guess you could argue it increases as the organism grows in size. Reason: The organism isn't mutating over time to become made of increasingly high entropy stuff, nor is it heating up. The entropy has to stay within an upper and lower bound. So over time the organism will increase entropy external to itself, while the internal entropy doesn't change very much, maybe just fluctuates within the bounds a bit.
It's probably better to talk about entropy per unit mass, rather than entropy density. Though mass conservation isn't an exact physical law, it's approximately true for the kinds to stuff that usually happens on Earth. Whereas volume isn't even approximately conserved. And in those terms, 1kg of gas should have more entropy than 1kg of condensed matter.
The organism isn't mutating over time to become made of increasingly high entropy stuff,
I mean, actually it is. Plus accumulation of various kinds of damage, experiences, etc. which makes it differ from other organisms.
nor is it heating up.
Looking it up, apparently people drop very slightly in temperature when they age, which I guess might dominate the entropy considerations (though I guess that is due to slowly dying, so it also seems compatible with entropy being related to life if reduction in life is related to reduction in entropy).
...The amount
I think the confusion may arise from this concept of 'entropy density'?
To compare density levels, we need to look at a specific volume or amount of matter (recall the units of entropy are energy over temperature, no reference to space or mass). In this closed system the 2nd law tells us that overall entropy only goes up, but it does not help us to differentiate between different areas of density. It also tells us that, overall, the density will increase over time, which is not intuitive.
Considering open systems makes things easier. Energy and matter can flow in and out. You can still sample your 'entropy density' in defined volumes, and you may indeed find that 'life has increased entropy locally'. But, through thermodynamic coupling, a greater amount of entropy has been exported to the environment. This coupling is the 'life engines' Dimitry and jessicata refer to.
In summary, the 'entropy density' concept needs to be considered carefully in local vs. global terms.
If you were to analyze which places life increases entropy and which places life decreases entropy, what would you decomposition look like?
Efficient heat engines locally slow entropy increase. If they could reverse entropy, they would (to get more energy out of things). They can also export high entropy (e.g. medium-temperature water) while intaking low entropy (e.g. un-mixed high and low temperature water) to locally reduce entropy. Entropy is waste from the perspective of a heat engine. Likewise, animals intake low-entropy food and excrete high-entropy waste.
Also, we typically think of utility-maximizers as wanting to decrease entropy. There's various attempts at formalizing this, e.g. Utility Maximization = Description Length Minimization. Could this account for some of the difficulty in alignment? Like if life wants to maximize entropy, and utility maximizers want to minimize entropy, that seems like a natural conflict. But there's a bunch of technical details that makes me unsure whether this logical actually works out.
Photosynthesis? Most of the carbon is bound from CO2 by using sun exergy.
Also you should halt and reevaluate your intuitions if they lead you to believe there is a perpetual motion machine.
I misread your whole post by thinking your title implied "your post would question whether the entropy increased=> the post argues it decreases" and then I was reading sloppily and didn't notice my error.
The usual materialist story of life I've heard is that life acts like an entropy pump, creating local reductions of entropy within the organism but increasing the entropy outside of the organism. (I think I've even seen that in The Sequences somewhere? But couldn't find it, feel encouraged to link it.) But I've come to think that might actually be wrong and life might increase entropy both inside and outside the organism.
Here's a rough account:
Am I missing something?