This instructable is for realistic extraterrestrial design. Star wars/trek have mostly got it wrong- too much like earth. This instructable is for creating things like the daggerwrist or skewer from Wayne Barlowe's Expedition. Remember the number one rule: Don't make things too much like earth

Step 1: Designing the World

This step speaks for itself. Just come up with details that could effect life- heat, geography, climate, gravity, air composition, and so on. Remember that this is what the lifeforms are based on; if you give the planet a low gravity there's going to be a lot of flying things.

Step 2: Food Chain

There must be an established food chain for any ecosystem to work. this is just common sense.

Step 3: Kingdoms of Life

You don't need to limit yourself to earth's animals, plants, fungi, and single cell organisms- try some things that are a combination of these things- like the plents of the Sagan 4 project. It really doesn't matter as long as you have a basis for a viable food chain.

Step 4: Animals- Sensors

Animals don't need the same senses earth creatures have. In Expedition the is almost an entirely planet wide lack of eyes, you can have vibration sensors, thermal pits, echolocation, or even bioelectrical sensors like those of sharks. You shouldn't, however, use telepathic energy- it is unscientific and these should be scientifically plausible worlds.

Step 5: Animals- Body Plan

Remember the first rule. We're not the pinnacle of evolution- not all planets will evolve like us. There is, however, some basic rules for life, creatures, at a certain point, will evolve something like a spine, there will be brains and hearts and blood- although not necessarily lungs.
Try some weird but plausible things to- tails with claws on them, natural air cannons, lungs in the form of a tube, etc.

Step 6: Animals- Feeding

There's no need to have jaws when there's so many interesting mouth parts out there. In Expedition the primary method of eating is liquivorious (animals pumping food full of enzymes then drinking them) and some creatures even eat through feeding grooves that act like cheese graters. Just remember that there's multiple ways to eat food.

Step 7: Animals- Reproduction

You need a way to keep your planet alive so you need to reproduce. Macroscopic animals can't do this asexually without dangerously cutting down on genetic diversity and you need to establish how they start the next generation. You can make different genders or make hermaphroditic creatures. Give them mating behaviors like changing colors or just have one sex have plates or whatnot.

Step 8: Planimals (Also Known As Plents)

Planimals are just plants/animals. They exhibit behaviors of both. They may move or may be stationary but they will have a heart, blood, a form of lung, and be able to use photo synthesis

Step 9: Plants

Plants still work on the same principles that they use on earth. One possible adaptation is gas bladders that allow them to rise above a forest canopy to get light.
There will still be things like grass, moss, seaweed, trees, and cacti (maybe not, depending on the planet's stage of development).
Seed dispersal will also be similar to earth except in a few cases such as ballooning fruit.
Leaf colors will be decided by the colors filtered through the atmosphere- we don't get a lot of green light so our plants don't absorb it as much.

Step 10: Fungi

These are necessary decomposers. They allow the dead life to return to the earth.

Step 11: Single Cell Organisms/Colonies

These aren't necessary to mention but it's always interesting to have slime molds.

Step 12: Civilized Life

DON'T MAKE IT TOO HUMANOID!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Remember the #1 rule and make differences. They only necessary similarity is a way to manipulate the environment. They don't need homes either- we do because we're so weak compared to other animals.
They will probably be mid-range predators; having the necessary brains to catch prey and the need to avoid predators.

Step 13: Just a Note

I'm lazy and this is just the basics. I'll be updating it later so keep checking.
<p>is it possible for there to be living planets or creatures the size of planets?</p>
while its true that we don't know what other life may look like, there are a few lessons we can learn from our own planet that are applicable in any environment: 1: Every higher animal has a head. Whether its a dinosaur, mammal, reptile, fish, or bird. A centralized area for sense organs close to the brain is a necessity, as it gives you one place on your body you must defend if attacked. That way, you don't have to worry about your nose on your back that you can't reach while the smaller animal feast on it. 2: Outside of the water, 4 main appendages are the minimum for easy movement. If it were any other way, you would see three legged creatures everywhere. In the case of the two legged creature above, a four legged predator would be able to dance around it, while spending less energy on keeping itself erect.
I'm going to argue with you on this: 1: Higher animals don't necessarily need heads. Although brains tend to be near the major sensory organs there's no reason the major sensory organs can't be in the body for reasons such as defense- the reason we have heads is that we have jaws- a development that requires sensory organs to be near it in mast cases. 2: Vertabretes on earth have four limbs because in the water fish evolved fins to move faster and have more control and they needed them to have equal power on opposite sides (without it they it's like paddling a rowboat with one oar) fish evolved four fins and we kept the trait. However, it's possible for limbs to bond together to create a wealth of tripeds. And also, two legs really help with maneuverability. It's really one of the reasons we survived (also freed upper limbs with hands that allow us to make good weapons).
you are correct about the heads, i meant that there's no point in having sense organs all over your body, i didn't mean they had to stick out. take an octopus for example. they're mouth is in the middle of their tentacles. we have four limbs not because of fish ( and by the way life needs a watery environment to start, chemicals don't mix enough in a rocky environment. I am including dense gases as liquid environments ) but because its the easiest way to stand and move, and symmetry is the easiest way to "code" in nature. true, we do walk on 2 legs now, but remember our arms used to be necessary for our primary mode of transportation, look at the great apes. What you have to look at is not where we are, but what forms got us here.
I'm not arguing about life needing a thick fluid to start. Just that creatures can evolve to have an odd number of legs if conditions are right. The gyrosprinter shown in step five has a front and back leg to make it fast but extremely maneuverable. It evolved from a creature with four limbs but the limbs fused to make turning easier. This is similar to dinosaur claws fusing to become the basis for the bird's wing.
you are incorrect, if the gyro tried to do a dime turn, it would fall over. using your example of birds, whens the last time you saw a bird running? Last time i checked, they run in wide arcs when trying to get away from something, not quick turns. this is why predators like fox and dogs and such are able to catch them while on the ground. and again, if two or three legs were beneficial to ground creatures AT ALL, we would see them on our planet. There are plenty of examples of creatures that used to have appendages and lost them ( reptile -> snake ), or creatures that had 2 flippers and a tail and went to 4 legs ( fish -> land creatures ) and creatures with 6 or 8 legs ( insects and spiders ) but no 2 or 3.
<p>the gyrosprinter has a balancing organ that stays parallel to the ground that keeps it up.</p>
Ostriches? Emu? Cassaway? Moa? The only problem any of them have with 4 leg predators is that they lay eggs. Yes, they started with more, but so did the original fish (something like 8 pairs of fins) You are saying that because it didn't, it couldn't. That's the same as arguing that dinosaurs were cold blooded because no reptiles today are warm blooded. Or that life couldn't exist out of the water because at one time it didn't.
Oh, and the gyro is obviously descended from 4 leg animal : )
There is absolutely no reason for a creature to go from 4 legs to 2 legs like that. What environmental pressure would make it beneficial to have fused front and back legs? Again, it would take much more energy to stand with fused legs, and make you much less agile. One could suggest that the creature could only walk on small paths, but then it would have stayed with four legs and not grown so large.
Once again: maneuverability. It could lean to the side and bend its spine to turn tightly while a creature with four legs couldn't.
I don't understand the early evolution of a skunk's ability to spray, or a spider's silk. That doesn't mean that I deny their possibility. Unlikely, very much; impossible, not so sure : )
What you don't get is that evolution is random, meaning that almost every conceivable form has been tried, and only a choice few remain, highlighting their superiority. Again, I'm talking about a rocky environment. try to stand the way the strider must, with your arms together and your feet together, and try to turn. Anyone with any imagination ( or engineers ) are able to immediately sense the implausibility of such a creature. Now, creatures with a "hip" and two side by side legs are fairly agile ( humans and the examples you gave ), but are by far the minority due to their special niche environments, and are short-lived geologically speaking ( with the exception of humans I hope ). The original fish had one fin, was shaped like a flatworm.
These wouldn't be by any chance be engineers like the ones who invented the bicycle and motorcycle?
I very much understand that evolution is random. You don't understand that it is limited by previous art : )
Just a minor thing- the first fish didn't really have any fins- just a tail.
The gyrosprinter hasn't evolved like a bird. It has one leg in front of the other not one leg next to the other. and most birds aren't really built for the whole running. they're fairly awkward on the ground (kiwis excluded) while ones on the ground and built to run are sort of like wild cats- built for mad dashes; sacrificing maneuverability for speed. The gyro has a flexible spine, good body structure, and amazing sense of balance. It would be better at turning than a Thompson's gazelle.
Cephalopods have heads, but the brain's spread out throughout the body. And, with their intelligence levels they would be considered higher animals. Also, while running it wouldn't need to the two legs would be useful because the animal would have two, thick legs as opposed to its four legged predator which runs in a gait that mimics the two legged one of the gyrosprinter. And, would have four, thinner legs which would be more prone to breaking from the force of running.
you apparently have no idea of how mechanical systems work. a two-legged creature such as the gyrosprinter would not be able to turn in a fast or efficient manner, and would be prone to falling over, especially in high wind or on unsure footing. As to your statement about four thinner legs being more prone to breakage from the "force of running", when was the last time you broke a leg while running? try this: get spore creature creator (free) and make a creature that resembles the gyrosprinter, you can check out a rudimentary example of how it would move. just look at its stride, the program compensates for balance and turning. when it runs straight, it looks ridiculous, because it is. i am tired of trying to educate you and expand your horizons, and am turning off new post notification so i no longer have to be infected with your ignorance.
I haven't actually broken my legs but there are multiple injuries that do occur from running one example being stress fractures. As for the gyrosprinter the possibility of lack of grip is actually a smaller problem than that of a four-legged animal this is because there-s only two feet to lose footing as opposed to the four possible points of failure. In case of high winds it could lean. I do have to ask if the creature creator extends the back as the gyrosprinter runs
I just want to point out that if one leg were to slip he would fall flat on his face, if the creature were built like other four legged creatures. Second, try tripping a centipede. If you're corect, it should be 50 times as likely to trip him, if I'm interpriting you're statement right.
&nbsp;The problem with the centipede argument is that, even though, the centipede has more points of failure they are less important. In the wild a 41 legged centipede should do about as well as a 42 legged one; a three legged elk, on the other hand, won't do as well as a four legged one.
I believe thats in complete opposition in what youv'e been saying. Also, with the whole 2vs4 leged creatures, with 2 legs being beter, I think we should take a look at humans. We have 4 limbs, 2 for mobilisation and 2 for manipulating objects. HOWEVER, under certain circumstances our arms are used like legs, either because of uneven terain or because of how steep it is. This proves that 4 legs are inherently better than 2 legs. BUT WAIT! Couldn't this be viewed the other way? If anything, this proves that a mixture of legs and arms provides the best mixture. Doesn't it? NO! It proves that however many limbs you have, they're useless if they're not used correctly. This excersise has been to merely ilustrate the point that while bad IDEAS are tolerable if you learn from them, bad REASONING should be corrected as soon as possible.
What an astute observation: &quot;Limbs are useless if used wrong&quot;, It could be applied to many other subjects, such as computer repair: &quot;Your computer isn't working because your using it wrong.&quot; And also, you misunderstood my argument. I'm not saying that any amount of legs is better than any other amount (although if there were an animal with thousands it would be a bit ridiculous) I was arguing that it could be advantageous for one specific animal to become bipedal--and also not in side-by-side configuration you were talking about. I will now add that your initial &quot;exercise&quot; was rather poorly thought out, as arms are only useful if they can manipulate things. It's not like an impala would become bipedal and have so many more options. It would still be an impala with an impala brain and impala hooves. If it had the hands and brain to make a tool or climb it would help, bot if not, it would just be a slower, more easily seen impala.
Other worlds with well developed life would be very different than our life. Even from the start, it wouldn't even use cells like ours. Because of this, the way the organisms get food, move, everything about them would be so different that those two things probably wouldn't even apply. It would all be so different that we just can't compare it to earth.
This is mostly true, but the cells would have some similarities such as flagella would probably be produced and there would be the same basic organelles.
Those things are still just things that we are so used to with life on earth. Whatever the equivalent would be on another planet would probably be very different. Cells are what have come from many different elements on earth put together over many years to make them what they are now. The process done over again (especially on a completely different planet) would produce something much different if anything was made at all.
I say that cell organelles are basically the same on other planets. at a small level like that there's going to be more similarity than the end result. It's like saying that abstract artists use completely different paints than more real ones.
I think there could be similarities, but not as many similarities as you think. Our cells are just one way to do it. I don't know how to really explain it other than saying the probability of something that similar showing up on a different planet is very low. Nature just found a different way over there. Also, with the 'It's like saying that abstract artists use completely different paints than more real ones.' comparison. When I read that I think of the paints being on the molecular scale in real life. Cells as something like the patterns or brush strokes which all add up to the picture.
Cells are cells, and must do one thing: reproduce. Symmetry is the natural result of cell reproduction. The only way to achieve three planes of symmetry, or an odd number of appendages, would be for cells to split into 3 when they reproduce. To jump from not reproduce to splitting into three is too much of a leap, therefore reproduction would create 2 cells, and an even number of appendages.
Care to explain 3 and 5 fold symmetry in plants? Or starfish?
Incorrect. If this was true we wouldn't have an odd number of digits. limbs can also bond. Like I said birds have all of their fingers bonded in the formation of wings. It's possible to have limbs bond in the same way.
... Where did that come from? I don't see anything about that in my post...
I'm not saying the cells are the same but they would be made (by nature not god) to achieve the same result, if a little different.
Ah, I see. I just didn't understand that part. I of course do agree with that.
<a rel="nofollow" href="http://en.wikipedia.org/wiki/Burgess_shale">Burgess shale</a>, anyone?<br/>
4 legs are an adaption from the way fish swim-the body moves side-to-side, a motion that is continued with reptiles like crocodiles. The proto-mammals developed an up-and-down running style, which created the motion of whales and seals. On land, a seal moves with 3 limbs.
A seal does have 4 limbs, the legs are stunted, and they are considered marine mammals. Besides, Bears tear the crap out of them on land, just reinforcing my statement
As you've stated they're marine mammals. Fish don't move that fast on land either.
Seals move on land with a 3 legged gait and Phorusrhacos tore the crap out of it's 4 legged prey. What's your point?
They technically use four limbs, but the back two are used as one.
Snakes? Kiwi? T-rex?
<p>Nice fantastic pictures!</p>
Cool Instructable I guess. The pictures are pretty wack-o crazy, but awesome anyways.
The really good drawings are from expedition, the other two are from the Sagan 4.
where are these pics from?
Expedition by Wayne Barlowe and also Sagan 4
but if there is less gravity there would be less air density, thus making it harder for creatures to maintain the low air-pressure above the wings/gliders and the necessary higher pressure below the wing/glider to keep it in the air
well, also remember that this is an ALIEN planet. the laws of physics (or something like that) might not be the same there as it is here
It is meant to be an alien planet in this universe so there is the same laws of physics, there's just some leeway in the gravity:atmospheric density ratio.

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