Evolving the Musculoskeletal System

Really? Would you say that a system of objects at complete thermal equiibrium (no thermal diversity) has low entropy, while a system of objects at diverse temperatures but containing the same total amount of thermal energy has comparatively higher entropy?I would suggest the exact opposite.Entropy does not equal diversity or complexity

Correct, but the context of the question was specific to living organisms.

Entropy in evolution works exactly the same way it does for all other matter and energy in the universe. The governing law of nature for entropy is called the Second Law of Thermodynamics (henceforth 2LOT), often summed up colloquially as "There ain't no such thing as a free lunch," or "You can't get something for nothing." 2LOT is why perpetual motion machines are impossible.No doubt the reason you're asking is that you've read or been told that the universe is running down and that it's impossible for things to improve or become more complex on their own. On the scale of the entire universe as a whole this is true, because there is nowhere for the universe to get additional energy since it already represents everything there is. But the Earth is not everything there is, and it gets huge amounts of energy daily from the sun that does all the work necessary to create increasing complexity.If the sun suddenly went out then life on Earth would soon become impossible. It takes energy for an acorn to become an oak, and without a constant input of new energy we would soon use up all natural resources on Earth. The entropy increases caused by our energy consumption, previously balanced by energy from the sun, would continue unchecked and that would be the end.--Percy

is it true that entropy degrades DNA over time?

No.Entropy doesn't do anything. It's a measure of something.

The Second Law of Thermodynamics (2LOT) states that the entropy in a closed system can never decrease. A closed system is like a box into which no energy or matter can enter, and no energy or matter can leave.2LOT means that if we had a closed system that contained nothing but a single DNA sample, its entropy could never decrease (decreasing entropy means increasing order, but in a chemical or physics sense, not in "clean up the room" sense). Certainly the entropy could increase, and if you want to interpret that as "degrade" then that's fine because giving you a more accurate interpretation would take some serious time.But 2LOT is the wrong way to approach biology. 2LOT is a fundamental law of nature. All matter and energy in the universe follow 2LOT, including the processes of evolution. That means that both random mutation and natural selection follow 2LOT, and all the other laws of nature. Evolution does not postulate any process that violates any law of nature.--Percy

I think you really mean to ask a different question, namely, does the second law of thermodynamics require that DNA degrade over time given the processes that DNA undergoes including, replication, mutation, etc.? I'm also sure that you are not talking about the DNA in a single individual, but whether DNA in progressive descendants of an individual must degrade over the sequence of generations.First, let me point out that my last formal life science class was 9th grade biology, and that you'll probably want a better answer than mine.I will suggest that as long as the organisms are not a closed system, it is not even inevitable that entropy for the DNA will even increase. So I suspect the answer is no, there is no requirement for DNA to degrade over time. I'm not aware of anything showing that DNA in humans has degraded compared to previous generations. Edited by NoNukes, : minor reformat

Yes, you are correct in that it is what I meant to say. The environment does not decay DNA to a less organized level as a function of time. Correct?

We are in a sense a solar powered organism. I'm curious to know why photosynthesis did not occur right from the beginning when single celled organisms emerged. Can anyone explain this?

That depends on what "the environment" is. Inside a living organism, there's no particular reason for DNA to decay. It may mutate but mutation is change, not decay. On the other hand, if DNA is just lying around on the ground, say in a pool of blood, there are various mechanisms by which it can degrade - and there's no way of "fixing" it.

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"It appears that many of you turn to Hebrew to escape the English...." -- Joseppi

The 2nd Law of thermodynamics does not require any such thing.What suggests to you that DNA is deteriorating?

Photosynthesis is hard. It takes a fairly complex series of enzymes and specialized organelles. The first living things engaged in incredibly simple metabolic chemistry because those reactions are a lot easier to catalyze and mediate with simple enzymes or ribozymes. The first "foods" were probably easily-reduced hydrogen compounds, like hydrogen sulfide.Photosynthesis emerged as a way not only to exploit the energy of the sun, but to exploit the capacity of water to act as the electron donor in the redox chemistry living things exploit for energy. (A redox reaction requires an electron donor (reducer) and an electron receptor (oxidizer)).

I was expecting that you would make an eventual tie-in to evolving the musculoskeletal system when you asked about entropy, but then you asked about the decay of DNA, and now about photosynthesis. Do your questions relate to the topic somehow?--Percy

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Yes, you are correct in that it is what I meant to say. The environment does not decay DNA to a less organized level as a function of time. Correct?

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Careful there.... If DNA were NOT subject to selection, then you'd be correct.... DNA would accumulate mutations over time and the organism would "degrade" from generation to generation. But, and this is an EXTREMELY important point, Organisms ARE subject to selection. Some mutations can be beneficial and result in INCREASED level of "organization." Mutations can bcome incorporated, or alter a gene function and improve an organism's chances to reproduce as compared to its peers. THAT'S HOW EVOLUTION WORKS!!!! But the increased function still reflects an INCREASE in entropy. It's counter-intiuitive if you think of entropy as a measure of "disorder" in a layman's sense, but that's how it works. Edited by Strongbow, : No reason given.

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Really? Would you say that a system of objects at complete thermal equiibrium (no thermal diversity) has low entropy, while a system of objects at diverse temperatures but containing the same total amount of thermal energy has comparatively higher entropy?

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I would suggest the exact opposite.

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Entropy does not equal diversity or complexity

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Strongbow writes:

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Entropy increases with diversity and complexity.
A completely uniform system has low entropy. A very complex and diverse system has higher entropy.

Really? Would you say that a system of objects at complete thermal equiibrium (no thermal diversity) has low entropy, while a system of objects at diverse temperatures but containing the same total amount of thermal energy has comparatively higher entropy?

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I would suggest the exact opposite.

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Entropy does not equal diversity or complexity

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As the possible states of a system increase, so does the entropy. Let's look at some examples.a: 000
b: 0000000Item b in the above example has more entropy.next example:a: 0000000 (can ONLY be 0)
b: 0000000 (each digit can only be 0 or 1)Again, b has the greater entropyNow the last one
a: 0000000
b: 1011001Again, B has the greater entropy. B is clearly more complex as well.Is that clearer? Still disagree?As for your example, I would agree that you're correct, but I'm not sure I'd describe it as more complex. Though it is more diverse... I have to scratch my head... it's been YEARS since Thermo class. Edited by Strongbow, : No reason given.Edited by Strongbow, : No reason given.