[mynah]

Scientists may soon be able to predict - at least in part - what organisms capable of surviving on the planets of distant suns would look like. According to an article in Scientific American, the colours of plants on distant worlds may differ strikingly from the greens dominating vegetation on earth, and may include black, red, orange and even luminous blue. If planets revolving around red dwarfs support photosynthetic plants, for example, these would probably be very dark in colour to absorb as much of the feeble light as possible. Supergiants, on the other hand, may promote the evolution of shiny blue plants that reflect much of the harsh light, etc.

[Moontanman]

Originally Posted by mynah

Scientists may soon be able to predict - at least in part - what organisms capable of surviving on the planets of distant suns would look like. According to an article in Scientific American, the colours of plants on distant worlds may differ strikingly from the greens dominating vegetation on earth, and may include black, red, orange and even luminous blue. If planets revolving around red dwarfs support photosynthetic plants, for example, these would probably be very dark in colour to absorb as much of the feeble light as possible. Supergiants, on the other hand, may promote the evolution of shiny blue plants that reflect much of the harsh light, etc.

Predicting what aliens might look like and the color of the chemicals plants might use to collect sunlight are really two different things. But for both we can use examples here on earth to guide us. Plants that use blue light on the earth have a tendency to be red (seaweeds) Or brown (seaweeds again) other wavelengths are used by yellow plants (algae) or purple (bacteria) Higher plants on the Earth us green colors to capture red and blue light. Coral use fluorescent colors to capture UV light and use it to make lower spectrum wave lengths and then use golden brown algae to make food from this light. there are so many possibility's here on the Earth we can really speculate with some assurance we will be right at least part of the time. The shape of life forms can also be worked out by using earth life as a template. anything that swims all the time will be more or less fish shaped. Land animals are less obvious but if we make certain assumptions we can again predict at least wide ideas. If land animals with back bone are present then we can predict animals that would at least resemble the animals of earth. the shape of herbivores would be at least similar to what we see and so would the predators. maybe on another world you might find hoofed predators instead of hoofed herbivores but that would just be details. If vertebrates don't evolve for some reason the things would become less familiar. this is a subject we can speculate on forever and never get bored

[mynah]

Admittedly, the title was pushing it a bit although I forgot to mention the rather important point that, according to the article, scientists should soon be able to determine whether life is present on distant planets or not.

Must say, convergent evolution is a fascinating subject. Hooves and fish-forms are especially interesting, considering the number of times these features arose. However, there are constraints to the evolution of these features, and sometimes they may be quite mundane: Although hooves seem to have arisen in three of the four main placental mammalian lineages (Laurasiatheria, Afrotheria and probably Atlantogenata) they have not appeared in Euarchonta (where they were probably not needed). In marsupials, however, more mundane constraints may have prevented the evolution of hoofed front limbs: The underdeveloped young require claws to climb into the pouch after birth.

It would be more difficult to predict which constraints apply on alien worlds - or, indeed, which that apply on earth are absent elsewhere. How common, for example, are vertebral columns, which appear to be a requirement - at least on earth - for the evolution of very large bodies on land? Would anyone have predicted starfish and octopus shapes had they not existed? As you say, one could go discussing the subject forever!

[Boerseun]

I think the most visible differences will be due to body chemistry. For instance, an octopus is pretty intelligent, and might have been the source of intelligent land-dwellers, were it not for its limitations due to its copper-based blue blood, which only holds around 8 times the oxygen than seawater. The land was eventually colonised by reptiles and mammals, who are able to hold much more oxygen in their blood due to heamoglobin, the iron-based carrier. So we'd think that evolution's final answer to life on land was us mammals, and animals that look like us. But this is only due to a small genetic accident, billions of years ago.

If the octopi's ancestors were able to use iron instead of copper as the oxygen carrier, then the Earth's landscape would have looked dramatically different. It could be argued that if that relatively mundane difference between iron and copper did take place for the octopi billions of years ago, whatever would have then been the intelligent species on Earth would have colonised the galaxy already. They have, after all, eight arms to our two, and should be able to evolve into forms much better able to manipulate their environment than we are. If the octopi swopped copper for iron, its almost a certainty that us humans would never have come to the fore.

[mynah]

The popular depiction of aliens as somewhat octopus-like is probably not too far-fetched... Octopi do have another problem, though: The lack of an internal skeleton would greatly constrain their size on land. (It is probably no accident that there are no really enormous land snails.)

I've often wondered what would have happened if that meteorite had not hit 65 million years ago. Would some really intelligent dinosaurs be building cities by now, or did evolution have to start almost from scratch (very basic, undifferentiated mammals) to produce us?

[UncleAl]

Google images
urey miller 11,600 hits

Life is constrained by chemistry and elemental abundance. Outworlder life will be wholly mistakable for the local inventory, extremophiles to Pacoima, CA. Whether your cell membranes are a soap bilayer or di-O-phytanyl glycerol ethers (Halobachium cutirubrum), whether your organelles are compartmentalized by ladderane carboxylates (anammox bacteria), whether you are one giant cell (Caulerpa taxifolia), whether you live at 60–70 MPa (9600 psi) rather than 0.1 MPa (hyperbarophiles)... we already have all that.

There will be no truly exotic outworlder life chemistries. The necessary compositional complexity of life, its supportive metabolisms, and information transfer with fidelity generation to generation places severe constraints on what chemistries will work.

the colours of plants on distant worlds may differ strikingly from the greens dominating vegetation on earth, and may include black, red, orange and even luminous blue.

In the terrestrial inventory, except possibly for a clean blue in photosynthesis.

[Moontanman]

Originally Posted by mynah

The popular depiction of aliens as somewhat octopus-like is probably not too far-fetched... Octopi do have another problem, though: The lack of an internal skeleton would greatly constrain their size on land. (It is probably no accident that there are no really enormous land snails.)

I've often wondered what would have happened if that meteorite had not hit 65 million years ago. Would some really intelligent dinosaurs be building cities by now, or did evolution have to start almost from scratch (very basic, undifferentiated mammals) to produce us?

I have actually seen some ideas that say the octopus like life forms might be able to overcome the lack of an internal skeleton. It was called future evolution and the lack of an internal skeleton was overcome by special muscle bundles doing the job of bones. I have caught octopus and even as they are now they can indeed crawl quite effectively for an animal with no bones and no support in air. In lower gravity an octopus might be a real threat. There are areas where octopus have been seen leaving the water to hunt rats so the idea may not be as far fetched as it seems.

If arthropods had evolved a more efficient way to breath they might have completely stifled the rise of vertebrates. There are lands crabs that are quite large and can actually tear apart coconuts for food While not as large as say a dog they are as large as a house cat and much more powerful. (Robber crabs or coconut crabs)

The was a study done to show the possibility of dinosaurs evolving intelligence. The result looked humanoid but clearly not human but I think the creatures doing the design (humans) influenced the outcome quite a bit.

[Moontanman]

Originally Posted by UncleAl

Google images
urey miller 11,600 hits

Life is constrained by chemistry and elemental abundance. Outworlder life will be wholly mistakable for the local inventory, extremophiles to Pacoima, CA. Whether your cell membranes are a soap bilayer or di-O-phytanyl glycerol ethers (Halobachium cutirubrum), whether your organelles are compartmentalized by ladderane carboxylates (anammox bacteria), whether you are one giant cell (Caulerpa taxifolia), whether you live at 60–70 MPa (9600 psi) rather than 0.1 MPa (hyperbarophiles)... we already have all that.

There will be no truly exotic outworlder life chemistries. The necessary compositional complexity of life, its supportive metabolisms, and information transfer with fidelity generation to generation places severe constraints on what chemistries will work.



In the terrestrial inventory, except possibly for a clean blue in photosynthesis.

UncleAl can you really say that life other than on the Earth would be chemically identical to ours? The same DNA, the same catalysts? Can you say for sure the ammonia cannot replace water? Hydrogen replace oxygen in respiration? Fats replace proteins? I will admit that a replacement for carbon is unlikely even on a bacteria level but arsenic might replace phosphorus. There are at least some chemicals used on the Earth that might be in use simply due to blind accident.

[Thunderbird]

I think the most fascinating aspect would be in symbiotic relationships.

Cooperative evolution between species might result in not only technologic multicultural societies, but based more in adaptive co-evolving multi-species societies, a higher level ecosystem if you will. Flying creatures becoming highly sophisticated information messengers. Sophisticated systems could be engineered though adaptation to utilize insects populations to plant ,maintain and harvest crops for species that build structures for cohabitation with the insects. Plants that coevolved with animals that provide eternal nurseries to creatures that develop bonds so intertwined they are both plant and animal. Parasitic-symbiotic relationships merging together forming what looks like one species but two, or sixty two, And finely a creature that has all the possible DNA sequences of all species on a very mature planet. A creature that could change its DNA sequence to such a degree it could essentially adapt to any form it choose. Now imagine a planet like this evolving over a period of 5-10 billion years of cooperative evolution....

[Moontanman]

Originally Posted by Thunderbird

I think the most fascinating aspect would be in symbiotic relationships.

Cooperative evolution between species might result in not only technologic multicultural societies, but based more in adaptive co-evolving multi-species societies, a higher level ecosystem if you will. Flying creatures becoming highly sophisticated information messengers. Sophisticated systems could be engineered though adaptation to utilize insects populations to plant ,maintain and harvest crops for species that build structures for cohabitation with the insects. Plants that coevolved with animals that provide eternal nurseries to creatures that develop bonds so intertwined they are both plant and animal. Parasitic-symbiotic relationships merging together forming what looks like one species but two, or sixty two, And finely a creature that has all the possible DNA sequences of all species on a very mature planet. A creature that could change its DNA sequence to such a degree it could essentially adapt to any form it choose. Now imagine a planet like this evolving over a period of 5-10 billion years of cooperative evolution....

I agree, I think that cooperation symbiosis has done as much as competition to cause evolution. Much of what we are is due to symbiosis. Mitochondria, chloroplasts, flagella, gut bacteria, it makes sense that symbiosis will continue in the future into larger and more wide spread groups of animals.