Let's create an alien biosphere!

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I suspect that the sulfate-reducing (and soon oxygen-reducing) organisms will form colonies around the hydrothermal vents. I think that we have already agreed that when a unicellular organism is approached by a predator, it will excrete reactive oxygen species in order to deter it. Perhaps the organisms will evolve to also release reactive oxygen species when a nearby organism is approached by a predator, and this will develop into more complex signalling pathways that eventually allow the cells to cooperate more efficiently as a multicellular organism.

We have to give the organisms a reason not to just cheat. What's stopping them from not doing their part and just relying on others? Maybe we can have them cannibalize slackers.

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We have to give the organisms a reason not to just cheat. What's stopping them from not doing their part and just relying on others? Maybe we can have them cannibalize slackers.

Predators will prefer to eat organisms that are not emitting reactive oxygen species in order to deter them. The reason that it's advantageous for nearby organisms to emit reactive oxygen species is because otherwise, the predator could go to them next.

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Predators will prefer to eat organisms that are not emitting reactive oxygen species in order to deter them. The reason that it's advantageous for nearby organisms to emit reactive oxygen species is because otherwise, the predator could go to them next.

Well there's still not enough reason for neighbours of emitting members to not just live off their protection.

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Well there's still not enough reason for neighbours of emitting members to not just life off their protection.

All organisms that get energy from oxidative phosphorylation produce reactive oxygen species; it's simply a matter of excreting more of them when predators are near.

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All organisms that get energy from oxidative phosphorylation produce reactive oxygen species; it's simply a matter of excreting more of them when predators are near.

Yeah, I guess you're right. They might now start a division of labor. The ones on the perimeter could secrete more reactive oxygen species for defense, while the ones on the inside produce and distribute energy. Are these autotrophs or heterotrophs?

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Yeah, I guess you're right. They might now start a division of labor. The ones on the perimeter could secrete more reactive oxygen species for defense, while the ones on the inside produce and distribute energy. Are these autotrophs or heterotrophs?

They are autotrophs. They perform oxidative phosphorylation.

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They are autotrophs. They perform oxidative phosphorylation.

Chemotrophs to be exact right? Also, if they're close enough to the surface and evolved horizontal gene transfer, they might acquire genes from photosynthesizers that help them detect light, or if the latter isn't true, then they could would evolve it on their own eventually anyway.

Question: What should we use to model or illustrate the life on the planet?

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Chemotrophs to be exact right?

Yes.

Also, if they're close enough to the surface and evolved horizontal gene transfer, they might acquire genes from photosynthesizers that help them detect light, or if the latter isn't true, then they could would evolve it on their own eventually anyway.

They aren't close to the surface yet, although that could change now that they can use dioxygen. However, they're probably going to run out of methane soon. There are multiple possible solutions to this. They could become scavengers or predators in order to get methane from other organisms. They could evolve to photosynthetically synthesize methane. They could split water directly then feed that into their electron transport chains. They could photosynthetically reduce the carbon in carbon dioxide via CO₂+SO₃⁻²→CO+SO₄⁻² then use hydrogen from photosynthetically splitting water to turn that into methane. If they use photosynthesis, one of the classes of pigment molecules that I think we discussed they could you is coordination complexes including at least one metal atom because the hydrothermal vents provide an ample supply of metal atoms. However, this would only work if the organisms are close to the water's surface, where they will have access to sunlight and dioxygen from the atmosphere, but I think that we had already agreed that the geologic activity would probably lift that part of the seafloor, so let's suppose that that happens now. The conjunction of two sources of energy and chemicals will likely lead to an explosion of diversity, with lineages upcurrent and downcurrent of the hydrothermal vents coming to the hydrothermal vents. (This will provide the organisms with an electron transport chain with a source of dioxygen, as there haven't been dioxygen-producing organisms for long enough for oxygen to have depleted everything that it can react with in the atmosphere and start accumulating.) It could lead to possibilities for horizontal gene transfer, and it will likely lead to predation.
By the way, is it okay if the organisms use sulfate instead of phosphate for information and energy storage? I think that sulfate is more likely because the increase geologic activity of this planet makes sulfur compounds more abundant.

[Schiaparelliorbust]

They aren't close to the surface yet, although that could change now that they can use dioxygen. However, they're probably going to run out of methane soon. There are multiple possible solutions to this. They could become scavengers or predators in order to get methane from other organisms. They could evolve to photosynthetically synthesize methane. They could split water directly then feed that into their electron transport chains. They could photosynthetically reduce the carbon in carbon dioxide via CO₂+SO₃⁻²→CO+SO₄⁻² then use hydrogen from photosynthetically splitting water to turn that into methane. If they use photosynthesis, one of the classes of pigment molecules that I think we discussed they could you is coordination complexes including at least one metal atom because the hydrothermal vents provide an ample supply of metal atoms. However, this would only work if the organisms are close to the water's surface, where they will have access to sunlight and dioxygen from the atmosphere, but I think that we had already agreed that the geologic activity would probably lift that part of the seafloor, so let's suppose that that happens now. The conjunction of two sources of energy and chemicals will likely lead to an explosion of diversity, with lineages upcurrent and downcurrent of the hydrothermal vents coming to the hydrothermal vents. (This will provide the organisms with an electron transport chain with a source of dioxygen, as there haven't been dioxygen-producing organisms for long enough for oxygen to have depleted everything that it can react with in the atmosphere and start accumulating.) It could lead to possibilities for horizontal gene transfer, and it will likely lead to predation.

Scavenging would only be a temporary solution, but it could last a while if scavengers/predators evolve relatively late and the dead bodies of microorganisms pile up. They would leak methane. Also, do we have the analogues of viruses on this planet? I'm not sure exactly how they might arise (which they probably would given the circumstances), but if they exist they could lead to a form of passive horizontal gene transfer.

By the way, is it okay if the organisms use sulfate instead of phosphate for information and energy storage? I think that sulfate is more likely because the increase geologic activity of this planet makes sulfur compounds more abundant.

Yes, that's totally fine.

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Scavenging would only be a temporary solution, but it could last a while if scavengers/predators evolve relatively late and the dead bodies of microorganisms pile up. They would leak methane.

Scavenging would likely be a stepping stone to predation. Perhaps the organisms evolve signal transduction pathways to go to dead photosynthesizers' bodies in order to absorb the leaking methane, adaptions that cause it to leak faster (e.g. piercing their membranes) would be favored, then this could transition to seeking methane from live photosynthesizers.

Also, do we have the analogues of viruses on this planet? I'm not sure exactly how they might arise (which they probably would given the circumstances), but if they exist they could lead to a form of passive horizontal gene transfer.

There are not viruses yet, and they didn't exist on Earth until after independent life evolved. Humans don't know exactly how viruses arose on Earth, but one possibility is that they evolved from plasmids, which bacteria can use for horizontal gene transfer. However, viruses must be able to attach to cell surface receptors in order to be able to enter host cells, and I don't think that the organisms have receptors for anything yet.

[Schiaparelliorbust]

Scavenging would likely be a stepping stone to predation. Perhaps the organisms evolve signal transduction pathways to go to dead photosynthesizers' bodies in order to absorb the leaking methane, adaptions that cause it to leak faster (e.g. piercing their membranes) would be favored, then this could transition to seeking methane from live photosynthesizers.

Something like a flagellum could be both used for piercing and locomotion.

There are not viruses yet, and they didn't exist on Earth until after independent life evolved. Humans don't know exactly how viruses arose on Earth, but one possibility is that they evolved from plasmids, which bacteria can use for horizontal gene transfer. However, viruses must be able to attach to cell surface receptors in order to be able to enter host cells, and I don't think that the organisms have receptors for anything yet.

AFAIK there are some theories that say that viruses might have evolved first. Also, by receptor do you mean any way of sensing the environment or something more specific?

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Something like a flagellum could be both used for piercing and locomotion.

Yes, or it could evolve to have some sort of pointy spike protein on its surface.

AFAIK there are some theories that say that viruses might have evolved first.

How would they have been able to multiply without hosts?

Also, by receptor do you mean any way of sensing the environment or something more specific?

I mean cellular signalling.

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Yes, or it could evolve to have some sort of pointy spike protein on its surface.

That sounds good to me.

How would they have been able to multiply without hosts?

I don't remember, but I know this video talks about it.

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That sounds good to me.

So I guess that once those scavengers evolve into predators, the prey organisms will evolve to excrete reactive oxygen species in response to detecting hydrogen sulfide.

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So I guess that once those scavengers evolve into predators, the prey organisms will evolve to excrete reactive oxygen species in response to detecting hydrogen sulfide.

Yes, I think we had already agreed on that. I also rewatched the video, and my favorite theory is the escape one, where self replicating bits of genetic material inside cells (which happens normally) somehow acquire a shell and escape the cell, becoming a virus. For the virus-first theory, it just said that there were self replicating bits of RNA before cells were around.

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I also rewatched the video, and my favorite theory is the escape one, where self replicating bits of genetic material inside cells (which happens normally) somehow acquire a shell and escape the cell, becoming a virus. For the virus-first theory, it just said that there were self replicating bits of RNA before cells were around.

I think that the most likely possibility is evolving from plasmids, but even that seems unlikely. It's quite possible that viral evolution is relatively unlikely and that Earth is an oddball in this respect, but we won't know until we are able to sample other planets.

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I think that the most likely possibility is evolving from plasmids, but even that seems unlikely. It's quite possible that viral evolution is relatively unlikely and that Earth is an oddball in this respect, but we won't know until we are able to sample other planets.

I would think that because viruses are relatively simple, they would evolve pretty easily.

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I would think that because viruses are relatively simple, they would evolve pretty easily.

They're simple compared to living things, but it's hard to imagine what they could evolve from. Maybe if some cells pick up DNA from the surrounding environment then form multicellular organisms, cells could use virus-like devices to share genes that they deem beneficial with each other.

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They're simple compared to living things, but it's hard to imagine what they could evolve from. Maybe if some cells pick up DNA from the surrounding environment then form multicellular organisms, cells could use virus-like devices to share genes that they deem beneficial with each other.

That sounds the best. The genetic packets would know how to make the target cell make more of them, and it would likely welcome the packet knowing that it will benefit it. Evolutionary success is about traits after all (which the packets/viruses are essentially). They would eventually mutate enough to lose their original purpose.

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That sounds the best. The genetic packets would know how to make the target cell make more of them, and it would likely welcome the packet knowing that it will benefit it. Evolutionary success is about traits after all (which the packets/viruses are essentially). They would eventually mutate enough to lose their original purpose.

The target cell might develop some way of judging whether the new gene is beneficial, e.g. whether taking it up causes the cell's stored energy to increase. This would likely confer immunity to viruses but open up other interesting possibilities.

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The target cell might develop some way of judging whether the new gene is beneficial, e.g. whether taking it up causes the cell's stored energy to increase. This would likely confer immunity to viruses but open up other interesting possibilities.

If they're multicellular, they might isolate the virus in an area of the "body", but the viruses might try getting around this by being initially beneficial or neutral. Also, beneficial viruses might be the most widespread at first. There's no rule saying that they have to be harmful.

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If they're multicellular, they might isolate the virus in an area of the "body", but the viruses might try getting around this by being initially beneficial or neutral. Also, beneficial viruses might be the most widespread at first. There's no rule saying that they have to be harmful.

Let's stop thinking about this until we get multicellular organisms. I remember that we spent several pages trying to figure out how photosynthesis could arise, then when we actually played things out, an opportunity for photosynthesis came up that we didn't anticipate. Let's not do the same thing here.

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Let's stop thinking about this until we get multicellular organisms. I remember that we spent several pages trying to figure out how photosynthesis could arise, then when we actually played things out, an opportunity for photosynthesis came up that we didn't anticipate. Let's not do the same thing here.

How did that happen exactly? I remember talking about dyes and stuff, but not much else.

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How did that happen exactly? I remember talking about dyes and stuff, but not much else.

They used polycyclic aromatic hydrocarbons made from graphite, which neither of us anticipated.

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They used polycyclic aromatic hydrocarbons made from graphite, which neither of us anticipated.

What do you think we should work on now then? I say we should keep talking about multicellular organisms.