Welcome Guest [Log In] [Register]
Speculative biology is simultaneously a science and form of art in which one speculates on the possibilities of life and evolution. What could the world look like if dinosaurs had never gone extinct? What could alien lifeforms look like? What kinds of plants and animals might exist in the far future? These questions and more are tackled by speculative biologists, and the Speculative Evolution welcomes all relevant ideas, inquiries, and world-building projects alike. With a member base comprising users from across the world, our community is the largest and longest-running place of gathering for speculative biologists on the web.

While unregistered users are able to browse the forum on a basic level, registering an account provides additional forum access not visible to guests as well as the ability to join in discussions and contribute yourself! Registration is free and instantaneous.

Join our community today!

Username:   Password:
Add Reply
Questions that don't need their own topics vol.2; New and fresh
Topic Started: Jan 4 2018, 11:18 AM (26,892 Views)
Rodlox
Superhuman
 *  *  *  *  *  *  *  *  *
Ragnar
Jan 14 2018, 06:38 AM
How could radial symmetry evolve to become the dominant body plan on an alien planet (presumably low gravity to super-earth) as opposed to the bilaterally symmetrical dominance we have here on Earth? After all, only echinoderms and cnidarians have followed radial symmetry and they're nothing more than the simplest of invertebrates.


P.S. Bonus - What would be the challenges they would face in terrestrial and flying niches?
Answers would be much appreciated!
dominant plan, or the dominant on land? if the latter, just have a radial group be one of the few who succeeds in moving past the tidepools.

the challenges would be the same as everyone else faces: avoiding drying out, finding places for their young, and moving from one place to another without tripping.
.---------------------------------------------.
Parts of the Cluster Worlds:
"Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP)
Offline Profile Quote Post Goto Top
 
Setaceous Cetacean
Member Avatar
Insert Funny Creative Title Here
 *  *  *  *  *
Rodlox
Jan 14 2018, 06:07 PM
Ragnar
Jan 14 2018, 06:38 AM
How could radial symmetry evolve to become the dominant body plan on an alien planet (presumably low gravity to super-earth) as opposed to the bilaterally symmetrical dominance we have here on Earth? After all, only echinoderms and cnidarians have followed radial symmetry and they're nothing more than the simplest of invertebrates.


P.S. Bonus - What would be the challenges they would face in terrestrial and flying niches?
Answers would be much appreciated!
dominant plan, or the dominant on land? if the latter, just have a radial group be one of the few who succeeds in moving past the tidepools.

the challenges would be the same as everyone else faces: avoiding drying out, finding places for their young, and moving from one place to another without tripping.
I also don't think there are any specific environmental factors favoring radial life-forms, but keep in mind that other factors could come into play. For instance, these radial creatures could have a more efficient circulatory system than their bilateral counterparts, or bilateral life might simply not evolve on this world.

Regarding flight, I can see it happening. Maybe small, hovering insectoids? I think flight above all would favor bilateral symmetry though, at least if they fly like birds. Radial ballonts might be a possibility for these creatures.
If you like balloons, the color red, or mixotrophic plants derived from photosynthetic vertebrate-analogues, then check out my xenobiology project Solais

Posted Image
Offline Profile Quote Post Goto Top
 
Sigmund Nastrazzurro
Member Avatar
Curator, Institute of Furahan Biology
 *  *  *  *
"How could radial symmetry evolve to become the dominant body plan on an alien planet?" If the orgamism AS A WHOLE is early as well as efficient, i.e. including circulation, nervous system, biomechanics, I see no problem.

"I think flight above all would favor bilateral symmetry though, at least if they fly like birds". But doesn't 'flying like a bird' of necessity include bilateral symmetry? I wouyld say that if you want a radial organism to fly is to make it fly NOT like a bird. Instead, they will have to evolve a system that is part and parcel of their radial symmetry. I think I found a potential solution once: just search my blog for 'tetropter' or have a look at these specific posts:

http://planetfuraha.blogspot.nl/2011/01/nereus-or-how-you-can-have-radial.html

http://planetfuraha.blogspot.nl/2009/07/originally-i-had-wanted-to-include.html (the fun part of that post was that someone actually made a flying radial robot using the same principle, so the concept has been independently validated).
"Never again, we vowed, would we let Natural History become a mere part of Human History" (Souren Nyoroge)
Visit the planet Furaha website and the corresponding blog
Offline Profile Quote Post Goto Top
 
IIGSY
Member Avatar
A huntsman spider that wastes time on the internet because it has nothing better to do
 *  *  *  *  *  *  *  *  *
Would it be possible for a large snail to evolved a radula specialized for eating calcareous algae? I was picturing a calcium enforced radula to slowly grind away at them, but that would wear down their radulas too. How could I get around this.
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
Offline Profile Quote Post Goto Top
 
CaledonianWarrior96
Member Avatar
An Awesome Reptile
 *  *  *  *  *  *  *  *
IGGSY
Jan 15 2018, 12:15 PM
Would it be possible for a large snail to evolved a radula specialized for eating calcareous algae? I was picturing a calcium enforced radula to slowly grind away at them, but that would wear down their radulas too. How could I get around this.
I don't know how fast radula can regrow back, if they actually can, but some older animals (especially carnivorans) tend to die quicker because of their teeth wearing down and not able to feed as well as when they're younger. So I guess for your snails this would just be a consequence of their lifestyle and their ultimately doomed to live a shorter life
Come check out and subscribe to my projects on the following subforums;

Future Planet (V.2): the Future Evolution of Life on Earth (Evolutionary Continuum)
The Meuse Legacy: An Alternative Outcome of the Mosasaur (Alternative Evolution)
Terra Cascus: The Last Refuge of the Dinosaurs (Alternative Evolution)
- Official Project
- Foundation
The Beryoni Galaxy: The Biologically Rich and Politically Complex State of our Galaxy (Habitational Zone)

- Beryoni Critique Thread (formerly: Aliens of Beryoni)
The Ecology of Skull Island: An Open Project for the Home of King Kong (Alternative Universe)
The Ecology of Wakanda: An Open Project for the Home of Marvel's Black Panther (Alternative Universe)

(Click bold titles to go to page. To subscribe click on a project, scroll to the bottom of the page and click "track topic" on the bottom right corner)


And now, for something completely different
Offline Profile Quote Post Goto Top
 
IIGSY
Member Avatar
A huntsman spider that wastes time on the internet because it has nothing better to do
 *  *  *  *  *  *  *  *  *
CaledonianWarrior96
Jan 15 2018, 12:54 PM
IGGSY
Jan 15 2018, 12:15 PM
Would it be possible for a large snail to evolved a radula specialized for eating calcareous algae? I was picturing a calcium enforced radula to slowly grind away at them, but that would wear down their radulas too. How could I get around this.
I don't know how fast radula can regrow back, if they actually can, but some older animals (especially carnivorans) tend to die quicker because of their teeth wearing down and not able to feed as well as when they're younger. So I guess for your snails this would just be a consequence of their lifestyle and their ultimately doomed to live a shorter life
I heard this is also the reason older tuataras eat softer prey like worms instead of arthropods
Projects
Punga: A terraformed world with no vertebrates
Last one crawling: The last arthropod

ARTH-6810: A world without vertebrates (It's ded, but you can still read I guess)

Potential ideas-
Swamp world: A world covered in lakes, with the largest being caspian sized.
Nematozoic: After a mass extinction of ultimate proportions, a single species of nematode is the only surviving animal.
Tri-devonian: A devonian like ecosystem with holocene species on three different continents.

Quotes


Phylogeny of the arthropods and some related groups


In honor of the greatest clade of all time


More pictures


Other cool things


All African countries can fit into Brazil
Offline Profile Quote Post Goto Top
 
Archeoraptor
Member Avatar
"A living paradox"
 *  *  *  *  *  *  *
Ragnar
Jan 14 2018, 06:38 AM
only echinoderms and cnidarians have followed radial symmetry and they're nothing more than the simplest of invertebrates.


I wouldn't consider echinoderms simple, they are not too far from chordates
though some have redeveloped bilateral symmetry to a point
Astarte an alt eocene world,now on long hiatus but you never know
Fanauraa; The rebirth of Aotearoa future evo set in new zealand after a mass extinction
coming soon......a world that was seeded with earth´s weridest
and who knows what is coming next...........

" I have to know what the world will be looking throw a future beyond us
I have to know what could have been if fate acted in another way
I have to know what lies on the unknown universe
I have to know that the laws of thee universe can be broken
throw The Spec I gain strength to the inner peace
the is not good of evil only nature and change,the evolution of all livings beings"
"
Spoiler: click to toggle
Offline Profile Quote Post Goto Top
 
Lowry
Member Avatar
ARH-WOOOOOOOOOOOOOOOOOOOO
 *  *  *  *  *
IGGSY
Jan 15 2018, 01:00 PM
CaledonianWarrior96
Jan 15 2018, 12:54 PM
IGGSY
Jan 15 2018, 12:15 PM
Would it be possible for a large snail to evolved a radula specialized for eating calcareous algae? I was picturing a calcium enforced radula to slowly grind away at them, but that would wear down their radulas too. How could I get around this.
I don't know how fast radula can regrow back, if they actually can, but some older animals (especially carnivorans) tend to die quicker because of their teeth wearing down and not able to feed as well as when they're younger. So I guess for your snails this would just be a consequence of their lifestyle and their ultimately doomed to live a shorter life
I heard this is also the reason older tuataras eat softer prey like worms instead of arthropods
Just putting this out there but chiton magnetite teeth are super awesome.
Projects Currently Being Worked Upon:

Karkinos: Where faith meets myth on a world of the strangely familiar.
Under New Suns: The forums own colonisation race! Steep yourself in my lore....

Projects in suspension (for when inspiration hits):

- Galapagaia
- Rich Man's Ark (nice little bit of community spec :P)
- Ichor

Projects for a latter day:




Offline Profile Quote Post Goto Top
 
Rodlox
Superhuman
 *  *  *  *  *  *  *  *  *
IGGSY
Jan 15 2018, 12:15 PM
Would it be possible for a large snail to evolved a radula specialized for eating calcareous algae? I was picturing a calcium enforced radula to slowly grind away at them, but that would wear down their radulas too. How could I get around this.
giant sloths inherited weak and fairly unarmored teeth...but they cobbled together extra layers of what they had, and made sure it was continuously growing - like the rodent-ish teeth of the aye-aye.

or look at human civilizations - sometimes the tools were little tougher than the rocks they were carving...it happens. (maybe have a series of teeth, using one or two at a time, and when they wear down, they're discarded in favor of the ones that're next in line)
Edited by Rodlox, Jan 15 2018, 03:46 PM.
.---------------------------------------------.
Parts of the Cluster Worlds:
"Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP)
Offline Profile Quote Post Goto Top
 
Hybrid
Member Avatar
May Specula Grant you Bountiful Spec!

Quote:
 
How could radial symmetry evolve to become the dominant body plan on an alien planet (presumably low gravity to super-earth) as opposed to the bilaterally symmetrical dominance we have here on Earth? After all, only echinoderms and cnidarians have followed radial symmetry and they're nothing more than the simplest of invertebrates.


I'm under the assumption that bilateral symmetry on some level is likely appear if active radial creatures attempted to become 'dominant'. The issue is that specializing in one direction of movement is a lot more efficient than just moving in all of them. While yes, radial creatures can move in many directions with little problem, picking just one allows things like streamlining, cephalization, and overall a creature that's more adapted at locomotion than their radial contemporaries. With that, it's just as simple as outcompeting them over time. Perhaps you might say "why not have a radial creature move mouth first? That would retain radial symmetry, specialize in one direction, and even have cephalization.". Don't forget that gravity exists. That's still going to create a dorsal-ventral differentiation, so when you add that to the front-back differentiation, you get bilateral symmetry.

The best evidence for this is the case of sea cucumbers, while slow, have very slight bilateral symmetry compared to other echinoderms. Compare a typical starfish with a particularly derived sea cucumber that even walks on legs, the sea pig. It's even hypothesized that originally, radial symmetry in echinoderms was the result of it being advantages for a sessile lifestyle of suspension feeding. Take that for what you will.

Maybe for your aliens, many have a similar condition of bilateral symmetry imposed over radial symmetry. Unless there's something I'm missing, a bilateral condition of some form seems likely for an active lineage.

(Also echinoderms are a lot more complicated than cnidarians, and are generally more complex than to some other animals. Generally speaking some of the most simplest animals don't really have much of a symmetry at all, such as placozoans.)
If I sound rude while critiquing, I apologize in hindsight!
"To those like the misguided; look at the story of Man, and come to your senses! It is not the destination, but the trip that matters. What you do today influences tomorrow, not the other way around. Love Today, and seize All Tomorrows!" - Nemo Ramjet
ノ( ͡° ͜ʖ ͡°)ヽ

Posted Image
Offline Profile Quote Post Goto Top
 
Rodlox
Superhuman
 *  *  *  *  *  *  *  *  *
Hybrid
Jan 15 2018, 06:44 PM
Quote:
 
How could radial symmetry evolve to become the dominant body plan on an alien planet (presumably low gravity to super-earth) as opposed to the bilaterally symmetrical dominance we have here on Earth? After all, only echinoderms and cnidarians have followed radial symmetry and they're nothing more than the simplest of invertebrates.


I'm under the assumption that bilateral symmetry on some level is likely appear if active radial creatures attempted to become 'dominant'. The issue is that specializing in one direction of movement is a lot more efficient than just moving in all of them. While yes, radial creatures can move in many directions with little problem, picking just one allows things like streamlining, cephalization, and overall a creature that's more adapted at locomotion than their radial contemporaries. With that, it's just as simple as outcompeting them over time. Perhaps you might say "why not have a radial creature move mouth first? That would retain radial symmetry, specialize in one direction, and even have cephalization.". Don't forget that gravity exists. That's still going to create a dorsal-ventral differentiation, so when you add that to the front-back differentiation, you get bilateral symmetry.
I think you may be conflating radial symmetry with spherical symmetry. radial already possess up-down differentiation.

as to cephalization, why? in which direction would you suggest a sea urchin or sand dollar cephalize? (starfish might cephalize one arm, as we see parallels of on Nereus, so I cede that point; but what of organisms which don't differ in distance from the center of the body?)
.---------------------------------------------.
Parts of the Cluster Worlds:
"Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP)
Offline Profile Quote Post Goto Top
 
Hybrid
Member Avatar
May Specula Grant you Bountiful Spec!

Quote:
 
I think you may be conflating radial symmetry with spherical symmetry. radial already possess up-down differentiation.

Oh no, that wasn't the intention. Radials certainly do have dorsal-ventral differentiation, that part was only relevant to the idea of what a radial creature that moves mouth first (Changing where up and down is on the body, think of a sea cucumber), but I was saying that gravity would like cause the new top and bottom of such creature to become different.

Quote:
 
as to cephalization, why? in which direction would you suggest a sea urchin or sand dollar cephalize? (starfish might cephalize one arm, as we see parallels of on Nereus, so I cede that point; but what of organisms which don't differ in distance from the center of the body?)

That's an interesting question. For something like sea urchins they would only need to change the way their body is positioned to have a mouth facing forwards, by walking on its side. After all, sea cucumbers likely descend from a similar arrangement, their closest relatives being sea urchins themselves.
If I sound rude while critiquing, I apologize in hindsight!
"To those like the misguided; look at the story of Man, and come to your senses! It is not the destination, but the trip that matters. What you do today influences tomorrow, not the other way around. Love Today, and seize All Tomorrows!" - Nemo Ramjet
ノ( ͡° ͜ʖ ͡°)ヽ

Posted Image
Offline Profile Quote Post Goto Top
 
Rodlox
Superhuman
 *  *  *  *  *  *  *  *  *
Hybrid
Jan 15 2018, 07:31 PM
Quote:
 
I think you may be conflating radial symmetry with spherical symmetry. radial already possess up-down differentiation.

Oh no, that wasn't the intention. Radials certainly do have dorsal-ventral differentiation, that part was only relevant to the idea of what a radial creature that moves mouth first (Changing where up and down is on the body, think of a sea cucumber), but I was saying that gravity would like cause the new top and bottom of such creature to become different.

Quote:
 
as to cephalization, why? in which direction would you suggest a sea urchin or sand dollar cephalize? (starfish might cephalize one arm, as we see parallels of on Nereus, so I cede that point; but what of organisms which don't differ in distance from the center of the body?)

That's an interesting question. For something like sea urchins they would only need to change the way their body is positioned to have a mouth facing forwards, by walking on its side. After all, sea cucumbers likely descend from a similar arrangement, their closest relatives being sea urchins themselves.
I nearly replied several times to your post - but each time, my reply grew into a new hypothetical organism...so I sketched them out. thank you for the conversation thus far and, hopefully, to come; its been quite helpful in crystalizing thoughts which'd been vague in my mind before now. (i hope to have been as useful to you as well)

the original in the upper left, is basically a sea urchin, or something along those lines. little feet around a mouth in the belly, with a digestive system that ejects food out the top of the body.

the lower left is something along the lines of a swimming sea cucumber or a squid - its abandoned any body armor it may've had, in favor of two pairs of triangular fins that stretch the length of the body. I would argue that this is not bilateral - but still radial, or biradial at most...because the axis still goes through its body in the same way. like a sea cucumber, it may be perpetually laying on its side, but the internal axis hasn't changed.

second from the left, however, is something that has changed its internal axis. it still poops out the top of its body, but the mouth has moved up to what used to be one of its sides. I picture this group of species as sessile reefbuilders, or the foundations where reefbuilders set up shop.

third from the left is something that outwardsly looks like its adopted bilateral symmetry...but what we see are the statocysts prompting spikes to grow upwards, no matter what angle the digestive system is at when the planktonic body settles on the sea floor to grow. the digestive tract could be upright | or diagonal \ or diagonal / or horizontal -- ...but the spikes always grow upwards.

the right one is the classic radial critter with legs all around it. i felt it couldn't be omitted, just for completeness sake. :)

however, one that I left out, is like the Sea Pigs, which aren't bilateral simply because of their body being long and mouth-led...but are bilateral because of their legs pointing in one direction.

Posted Image
Edited by Rodlox, Jan 16 2018, 12:50 AM.
.---------------------------------------------.
Parts of the Cluster Worlds:
"Marsupialless Australia" (what-if) & "Out on a Branch" (future evolution) & "The Earth under a still sun" (WIP)
Offline Profile Quote Post Goto Top
 
CaledonianWarrior96
Member Avatar
An Awesome Reptile
 *  *  *  *  *  *  *  *
So I asked a similar question to what I'm going to ask on the last thread but it never got answered so here goes this one.

Would it be possible for australian bat species to be able to travel across the Tasman sea over to New Zealand, whether for migratory purposes or to establish a resident population? I'm assuming current New Zealand species travelled over when the Tasman sea was smaller in the past
Come check out and subscribe to my projects on the following subforums;

Future Planet (V.2): the Future Evolution of Life on Earth (Evolutionary Continuum)
The Meuse Legacy: An Alternative Outcome of the Mosasaur (Alternative Evolution)
Terra Cascus: The Last Refuge of the Dinosaurs (Alternative Evolution)
- Official Project
- Foundation
The Beryoni Galaxy: The Biologically Rich and Politically Complex State of our Galaxy (Habitational Zone)

- Beryoni Critique Thread (formerly: Aliens of Beryoni)
The Ecology of Skull Island: An Open Project for the Home of King Kong (Alternative Universe)
The Ecology of Wakanda: An Open Project for the Home of Marvel's Black Panther (Alternative Universe)

(Click bold titles to go to page. To subscribe click on a project, scroll to the bottom of the page and click "track topic" on the bottom right corner)


And now, for something completely different
Offline Profile Quote Post Goto Top
 
Empyreon
Member Avatar
Are you plausible?

Bats are a relatively high energy animal, and as such need a pretty constant food source. Travel over water, for whatever reason, would be a tall order IMO. I could be wrong of course, but I think I would agree with your assumption that bats of New Zealand would have crossed the Tasman Sea when it was much narrower, and are now effectively stranded.
Take a look at my exobiology subforum of the planet Nereus!

COM Contributions


food for thought
Offline Profile Quote Post Goto Top
 
2 users reading this topic (1 Guest and 0 Anonymous)
Members: Icthyander
Go to Next Page
« Previous Topic · General Spec · Next Topic »
Add Reply