History SoYouWantTo / CreateBelievableAliens

27th Jun '17 5:16:09 PM nombretomado
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Of course, you can't respond to a stimulus unless you can ''detect'' that stimulus, hence the evolution of senses. Of great benefit was the sense of sight. Vision evolved independently no less than ''sixty-four different times'' within different animal classes. The first "eyes" were nothing more than a light-sentitive patch of skin, attached to a nerve that sent different signals depending on how much light was received. Just the ability to detect the difference between being in light and darkness had a huge survival advantage; if the lights suddenly went out, it likely meant that a predator was casting its shadow on you, and by running in a random direction you might be able to escape. TheOtherWiki has an article on [[http://en.wikipedia.org/wiki/Evolution_of_the_eye the evolution of the eye]]. What's important to note is the ''convergence'' of eye evolution in different species. Human and octopus eyes, for example, evolved totally independently of one another, yet their similarity in structure is striking -- in some ways, an octopus eye is ''better'' than a human eye, in that there are no blood vessels cluttering the area in front of the octopus's retina. Many insects have "compound eyes", which are basically a retina turned inside-out -- each facet on a fly's eye can see only one "pixel" of the world around it, and it assembles a vague, low-resolution picture of its surroundings from these pixels.

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Of course, you can't respond to a stimulus unless you can ''detect'' that stimulus, hence the evolution of senses. Of great benefit was the sense of sight. Vision evolved independently no less than ''sixty-four different times'' within different animal classes. The first "eyes" were nothing more than a light-sentitive light-sensitive patch of skin, attached to a nerve that sent different signals depending on how much light was received. Just the ability to detect the difference between being in light and darkness had a huge survival advantage; if the lights suddenly went out, it likely meant that a predator was casting its shadow on you, and by running in a random direction you might be able to escape. TheOtherWiki Wiki/TheOtherWiki has an article on [[http://en.wikipedia.org/wiki/Evolution_of_the_eye the evolution of the eye]]. What's important to note is the ''convergence'' of eye evolution in different species. Human and octopus eyes, for example, evolved totally independently of one another, yet their similarity in structure is striking -- in some ways, an octopus eye is ''better'' than a human eye, in that there are no blood vessels cluttering the area in front of the octopus's retina. Many insects have "compound eyes", which are basically a retina turned inside-out -- each facet on a fly's eye can see only one "pixel" of the world around it, and it assembles a vague, low-resolution picture of its surroundings from these pixels.
25th Oct '16 7:04:11 PM nombretomado
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This is not an easy task. GeorgeRRMartin said as much in his 1976 essay "First, Sew On a Tentacle (Recipes for Believable Aliens)". Your alien species will come from a world with its own evolutionary history, its own flora and fauna -- if distinctions like "flora" and "fauna" even make sense in that world's biosphere -- and must occupy some evolutionary niche on that world, or by all rights it shouldn't exist at all.


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This is not an easy task. GeorgeRRMartin Creator/GeorgeRRMartin said as much in his 1976 essay "First, Sew On a Tentacle (Recipes for Believable Aliens)". Your alien species will come from a world with its own evolutionary history, its own flora and fauna -- if distinctions like "flora" and "fauna" even make sense in that world's biosphere -- and must occupy some evolutionary niche on that world, or by all rights it shouldn't exist at all.

18th Jun '16 5:47:23 PM evanator66
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Of course, distinctions like "warm blooded" or "cold blooded", and "herbivore" or "carnivore", are ''terrestrial'' ones. The alien biosphere might not have the sharp dichotomy between plants and animals that exists on Earth -- it may have mobile creatures with central nervous systems like animals, who subsist on photosynthesis (and a bit of decaying dead organic matter) like plants. But however they live, there must be ''something'' in their basic survival psychology that pushes them to explore, or they're never going to build space ships in the first place.

to:

Of course, distinctions like "warm blooded" or "cold blooded", and "herbivore" or "carnivore", are ''terrestrial'' ones. The alien biosphere might not have the sharp dichotomy between plants and animals that exists on Earth -- it may have mobile creatures with central nervous systems like animals, who subsist on photosynthesis (and a bit of decaying dead organic matter) like plants. But however they live, there must be ''something'' in their basic survival psychology that pushes them to explore, or they're never going to build space ships in the first place.place.

Once you've got the basics of your species' psychology figured out, consider checking out SoYouWantTo/DesignAnAlienMind to flesh out the rest of the thought processes of your new aliens.
10th May '16 12:21:41 PM hillo315
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But the genetic code we have today -- a mapping of 64 different nucleotide combinations to 20 different amino acids -- is not universal to all life forms on Earth. The mitochondria inside your cells, for example, have their own DNA and replicate themselves according to their own drummer, but their genetic code is slightly different from the genetic code in your cell nuclei. It's ''mostly'' the same, but not ''entirely'' the same. An RNA/DNA using organism that evolved on another planet could --and, indeed, almost certainly ''would'' -- have an entirely different genetic code. Maybe they only make use of 16 amino acids, not 20, and get away with having codons that are only 2 nucleotides long instead of 3. Maybe they don't use amino acids to build their bodies but something else, and that something else has 10,000 variants instead of 20; if they use 4-nucleodite RNA/DNA like we do, each codon would have to be at least 14 nucleotides long.

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But the genetic code we have today -- a mapping of 64 different nucleotide combinations to 20 different amino acids -- is not universal to all life forms on Earth. The mitochondria inside your cells, for example, have their own DNA and replicate themselves according to their own drummer, but their genetic code is slightly different from the genetic code in your cell nuclei. It's ''mostly'' the same, but not ''entirely'' the same. An RNA/DNA using organism that evolved on another planet could --and, indeed, almost certainly ''would'' -- have an entirely different genetic code. Maybe they only make use of 16 amino acids, not 20, and get away with having codons that are only 2 nucleotides long instead of 3. Maybe they don't use amino acids to build their bodies but something else, and that something else has 10,000 variants instead of 20; if they use 4-nucleodite 4-nucleotide RNA/DNA like we do, each codon would have to be at least 14 nucleotides long.



Of course, distinctions like "warm blooded" or "cold blooded", and "herbivore" or "carnivore", are ''terrestrial'' ones. The alien biosphere might not have the sharp dichotomy between plants and animals that exists on Earth -- it may have mobile creatures with central nervous systems like animals, who subsist on photosynthesis (and a bit of decaying dead organic matter) like plants. But however they live, there must be ''something'' in their basic survival psychology that pushes them to explore, or they're never going to build space ships in the first place.

to:

Of course, distinctions like "warm blooded" or "cold blooded", and "herbivore" or "carnivore", are ''terrestrial'' ones. The alien biosphere might not have the sharp dichotomy between plants and animals that exists on Earth -- it may have mobile creatures with central nervous systems like animals, who subsist on photosynthesis (and a bit of decaying dead organic matter) like plants. But however they live, there must be ''something'' in their basic survival psychology that pushes them to explore, or they're never going to build space ships in the first place.
20th Nov '14 2:51:31 PM tracer
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But pretty soon, one sub-group of the mammals, called the therapsids, hit upon another strategy for thermal regulation. They produced extra heat ''inside their own bodies'' via chemical reactions. The glucose respiration their cells relied upon for energy also gave off some heat, so by "burning" extra glucose they could keep themselves warm even when the environment got cold. We call it ''endothermy'' (not to be confused with an endothermic chemical reaction, which is a reaction that absorbs heat rather than giving it off; animal endothermy requires exothermic chemical reactions). Endothermy allowed them to keep active on cold nights, when other animals could barely move, and to survive in colder climates.

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But pretty soon, one sub-group of the mammals, reptiles, called the therapsids, hit upon another strategy for thermal regulation. They produced extra heat ''inside their own bodies'' via chemical reactions. The glucose respiration their cells relied upon for energy also gave off some heat, so by "burning" extra glucose they could keep themselves warm even when the environment got cold. We call it ''endothermy'' (not to be confused with an endothermic chemical reaction, which is a reaction that absorbs heat rather than giving it off; animal endothermy requires exothermic chemical reactions). Endothermy allowed them to keep active on cold nights, when other animals could barely move, and to survive in colder climates.
19th Nov '14 7:13:31 PM tracer
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Added DiffLines:

By the end of the Paleozoic era, therapsids had diversified until they filled nearly the same ecological niches as the mammals of today. There were great grazing herds that roamed the grasslands, there were predators who fed on the grazing herds, there were tree-dwelling arboreals, there were coastal swimmers; nearly every niche filled by a mammal today had an analog among the therapsids. An alien visitor would find little difference between Earth at the end of the paleozoic and Earth in the modern era.

And then, disaster struck.
19th Nov '14 7:01:48 PM tracer
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Eventually, reptiles emerged, who produced hard-shelled eggs that could be safely stowed away on land. They out-competed the amphibians in much the same way that the amphibians had out-competed the insects. But like the insects, the fish, and the amphibians -- in fact, like every other organism living on Earth at this point in history -- reptiles were cold-blooded. Their body temperature depended entirely on the temperature of their surroundings.

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Eventually, reptiles emerged, who produced hard-shelled eggs that could be safely stowed away on land. They out-competed the amphibians in much the same way that the amphibians had out-competed the insects. But like the insects, the fish, and the amphibians -- in fact, like every other organism living on Earth at this point in history -- reptiles were cold-blooded. Their body temperature depended entirely on the temperature of their surroundings.
surroundings. Since a lot of biological processes depend on chemical reactions that only happen within a certain narrow range of temperatures, they had to evolve all sorts of tricks to keep warm. Some got large enough that they wouldn't lose heat very quickly in cold weather. Some evolved enormous sails on their backs which they could turn toward the sun for gathering heat, and then fold up at night to prevent heat loss.

But pretty soon, one sub-group of the mammals, called the therapsids, hit upon another strategy for thermal regulation. They produced extra heat ''inside their own bodies'' via chemical reactions. The glucose respiration their cells relied upon for energy also gave off some heat, so by "burning" extra glucose they could keep themselves warm even when the environment got cold. We call it ''endothermy'' (not to be confused with an endothermic chemical reaction, which is a reaction that absorbs heat rather than giving it off; animal endothermy requires exothermic chemical reactions). Endothermy allowed them to keep active on cold nights, when other animals could barely move, and to survive in colder climates.

Warm bloodedness came at a price, however. To produce all that chemical heat, you needed much more glucose than you'd use otherwise. Over 75% of the glucose consumed by a human's metabolism goes solely into producing heat, for example. That means needing a ''lot'' more food. A warm blooded creature has to eat, and eat, and eat, nearly all the time. The 3 meals a day we humans take for granted as normal is in stark contrast to the one meal every week, or every month, that a reptile needs. As a consequence, a much smaller percentage of warm blooded creates could afford to be carnivores. While 1 in 5 cold-blooded fish or reptiles is carnivorous, only about 1 in 100 warm-blooded creatures are carnivorous, because a warm-blooded carnivore has to kill and eat a lot more prey than a cold-blooded one does. (Kinda backwards from the notion of the "cold-blooded killer," isn't it?)

On an alien world, there's no guarantee that endothermy would have evolved as the dominant strategy for thermal regulation. Sails, fins, or gigantothermy could have taken over. So could the strategy of the Galapagos diving iguanas, who sunbathe on rocks and then immerse themselves in the cold oceans for a short time to make use of their stored heat. Other strategies that never appeared on Earth are also possible.
19th Nov '14 6:31:54 PM tracer
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Added DiffLines:

Eventually, reptiles emerged, who produced hard-shelled eggs that could be safely stowed away on land. They out-competed the amphibians in much the same way that the amphibians had out-competed the insects. But like the insects, the fish, and the amphibians -- in fact, like every other organism living on Earth at this point in history -- reptiles were cold-blooded. Their body temperature depended entirely on the temperature of their surroundings.
19th Nov '14 6:12:08 PM tracer
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Much is made about the "first animals to leave the oceans", with most folks usually pointing to either lizard-like amphibians that used their arms for brachiation under water, or lungfish that could pull themselves across land for short distances. The people that think these were the first animals to leave the oceans are ''hopelessly'' vertebrate-centric in their thinking. The first land animals weren't fish. They weren't amphibians. They were '''insects.''' Insects evolved the ability to breathe air and survive on land 40 million years before vertebrates did. With no vertebrate predators to threaten them, some of these insects grew to nearly 3 feet long. They couldn't get any bigger than this, though; without an endoskeleton, all the squishy guts inside their bodies have to be anchored to the inside of their chitinous exoskeletons. The bigger the insect, the more those guts will inevitably "sag" toward the bottom of their body cavity, and the thicker (relative to the overall length of the insect) the exoskeleton needs to be. It's the insect version of the SquareCubeLaw, and it piles up a lot quicker than the square-cube law does for us bones-on-the-inside vertebrates.

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Much is made about the "first animals to leave the oceans", with most folks usually pointing to either lizard-like amphibians that used their arms for brachiation under water, or lungfish that could pull themselves across land for short distances. The people that think these were the first animals to leave the oceans are ''hopelessly'' vertebrate-centric in their thinking. The first land animals weren't fish. They weren't amphibians. They were '''insects.''' Insects evolved the ability to breathe air and survive on land 40 million years before vertebrates did. With no vertebrate predators to threaten them, some of these insects grew to nearly 3 feet long. They couldn't get any bigger than this, though; without an endoskeleton, all the squishy guts inside their bodies have to be anchored to the inside of their chitinous exoskeletons. The bigger the insect, the more those guts will inevitably "sag" toward the bottom of their body cavity, and the thicker (relative to the overall length of the insect) the exoskeleton needs to be. It's Compoounding this problem was the need to extract oxygen from the air. Insects have neither lungs nor oxygen-carrying blood; they have to draw air in from ''spiracle'' valves on their skin, and carry it directly to the tissues through networks of tiny tubes. This means no point inside an insect's body can be more than a couple of centimeters from its exterior.[[note]]The earth's atmosphere also had a higher partial pressure of oxygen in the Paleozoic than it does today. A three-foot-long insect would probably asphyxiate in today's air.[[/note]] These twin problems form the insect version of the SquareCubeLaw, and it piles up a lot quicker than the square-cube law does for us bones-on-the-inside vertebrates.
19th Nov '14 6:00:01 PM tracer
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Eventually, some of these chordates found a new niche to inhabit, that no animals had inhabited before: The brackish, less-salty-than-the-ocean waters at the mouths of river deltas. They of course had to evolve a kidney to expel all the excess water they took on in these low-salinity environments, but they also faced another problem. Sodium salts aren't the only salts dissovled in ocean water. There are a lot of minerals in sea water, including calcium, and calcium had long ago become a mineral that much of their biology depended on. So, now, they needed a way to ''store'' calcium inside their bodies, for those times when the brackish waters didn't have enough calcium dissolved in them for their daily needs. Big lumps of calcium have the approximate consistancy of rocks, so they needed a place in their bodies to store these "calcium rocks" which wouldn't interfere with their breathing, eating, mobility, etc.. What better place to store them than ''hanging in little bundles off of their notochords!'' This is how the notochord gradually became a true ''backbone''. Eventually these lumps of calcium started getting formed into deliberate, interlocking shapes which could flex between the segments without wasting space or pinching the notochord (now called the spinal cord) they were wrapped around.

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Eventually, some of these chordates found a new niche to inhabit, that no animals had inhabited before: The brackish, less-salty-than-the-ocean waters at the mouths of river deltas. They of course had to evolve a kidney to expel all the excess water they took on in these low-salinity environments, but they also faced another problem. Sodium salts aren't the only salts dissovled in ocean water. There are a lot of minerals in sea water, including calcium, and calcium had long ago become a mineral that much of their biology depended on. So, now, they needed a way to ''store'' calcium inside their bodies, for those times when the brackish waters didn't have enough calcium dissolved in them for their daily needs. Big lumps of calcium have the approximate consistancy consistency of rocks, so they needed a place in their bodies to store these "calcium rocks" which wouldn't interfere with their breathing, eating, mobility, etc.. What better place to store them than ''hanging in little bundles off of their notochords!'' This is how the notochord gradually became a true ''backbone''. Eventually these lumps of calcium started getting formed into deliberate, interlocking shapes which could flex between the segments without wasting space or pinching the notochord (now called the spinal cord) they were wrapped around.
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