Alien Biosphere Evolution #6: Size and the Modularity of Life

When it comes to the evolution of life on Earth or other planets the general rule is that: Probabilities decrease with increasing specificity. The more specific a life form, the less likely it is that it will evolve naturally. A humanoid being, for instance, though often the staple of science fiction, may actually be relatively unlikely, because of the long chain of contingent events needed to arrive at it. That doesn’t mean anything more specific is implausible, but just that we can expect it to be less common in the universe. No matter what, we can be certain about one thing: Life will start out tiny. From mere molecules to minute microbes, life on any exoplanet far, far away, will probably be stuck at microscopic scales at first and remain so for aeons. That is because, starting from such humble beginnings, evolving creatures need to achieve key innovations in order to break through into the macroscopic world. So what are some of the strategies employed by living systems during evolution to attain ever greater sizes and is there a single universal trend? Let's find out!
0:00 Introduction
1:07 Life's microscopic Origins
4:00 Complex Cells
7:12 Multicellularity
9:35 Tissue specialization
11:53 Closing thoughts
12:34 Next video: Deep Body Patterning
SOCIAL MEDIA:
Website: www.phrenotopia.com/
Twitter: / phrenotopian
REFERENCES (Under Construction!)
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- Mángano MG & Buatois LA (2014) "Decoupling of body-plan diversification and ecological structuring during the Ediacaran-Cambrian transition: evolutionary and geobiological feedbacks" Proc. R. Soc. B 281 | doi.org/10.1098/rspb.2014.0038
- ...
CREDITS (Under Construction!)
Images:
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- A plethora of images of extinct animals were created by paleo-artist Nobu Tamura and available here: spinops.blogspot.com/ & www.deviantart.com/ntamura
- "Kepler-186f" by NASA Ames/JPL-Caltech/T. Pyle | www.nasa.gov/ames/kepler/kepl...
- "Earth-like Exoplanet" by Scott Richard
- www.pexels.com/
- pixabay.com
Footage:
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- "Lipid Bilayer (Cell Membrane)" by @Ragdoll Studio LLC | • Lipid Bilayer (Cell Me...
- "Gold Farm" courtesy of @Sylle7 bit.ly/Sylle7YT
- pixabay.com/videos/
Music:
- "Backyard Safari" by TechSmith
- "What Does Anybody Know About Anything" by Chris Zabriskie | chriszabriskie.com/ | CC BY 4.0
- "Digital Memories" by @Unicorn Heads
- "Sprite Star" by @Saibysed | / saidbysed
- "Progressive Chords Lead" by Frankum | / frankumjay
- "Kick and Progressive Leads" by Frankum

[@thejellyfishmon9261]

Im glad speculative evolution is becoming popular and i especially enjoy this series its extremely helpful and i love how in-depth it go’s, keep up the great work!

[@fralegend0152]

mmh, I've seen you somewhere else...

[@leiram8833]

I agree! I randomly found this channel this morning and am so excited! Speculative evolution is my favorite!

[@joaquimpereira4995]

I´ve always found the fact that endosymbiosis actually happened remarkably lucky. I mean, what are the odds that a smaller cell with aerobic capability would enter a larger cet, not get digested and somehow establish a perfect symbiotic link with the other cell, even dividing at the same time? It is true how evolution depends on a lot of, how Bob Ross would put it, "happy accidents" in order to progress.

[@Phrenotopia]

It actually happened multiple times, so I don't it's unlike at all. In fact, it also happens on higher levels such as in corals and lichens. I think the transition is very gradual like with regular kinds of symbiosis.

[@Dragrath1]

Yeah Eukaryotic life does seem to be quite exceptional in that there isn't really other lineages of similar complexity known but we should note there is evidence it didn't all happen at once. In particular as we get a better sampling of anaerobic life the Archaea seem to capture a fair amount of intermediate steps The Asgard phylum of Archaea in particular contain a lot of genes previously known only from Eukaryotes. Just last year Japanese researchers published their findings on studying and culturing one of the Lokiarchaeota the first of the phylum to be identified based off metagenomic sampling which they named Prometheoarchaeum Syntrophicum and they found it had "tentacles" which it used to grasp onto other microbes which metabolize its own waste products and produce things it needs that it can't make on its own and vice versa. It is effectively a symbiotic relationship but one where the Prometheoarchaeum has disproportionate control both physically and metabolically. Now among the Asgard phylum this is one of the more distantly related branches compared to where Eukaryotes appear to map within the clade so it isn't conclusive but it strongly supports an inside out approach to endosymbiosis where a more complex archaean microbe over time acquires more and more of the genome of its exosymbiotes genes via horizontal gene transfer allowing it to exert more and more control over its symbiotic partners. It seems to be surprisingly like domestication at the unicellular level. Prometheoarchaeum is notably completely anaerobic with a very low metabolic rate and reproduces quite slowly with the time to double in population taking over twenty days but it is hypothesized that perhaps a relative could have captured an aerobic bacterium in response to the rise in oxygen levels allowing it to eventually "domesticate" the bacterium and later endosymbiotically encapsulate its microbial livestock. It would still be a monumental leap as it would need to capture or offer something in exchange that a aerobic microbe was unable to do as the electron recipient used in respiration seems to be hard to swap with few organisms capable of more than one type as such respitory reactants are mutually incompatible being mutually toxic to each other and a host organism with oxygen being one of the most dangerous electronegative recipients. In fact the only thing with stronger electronegativity or oxidation numbers are halogens like Florine which thus far life has failed to make use of for respiration. Sulfur based respiration was almost certainly a prerequisite or corequisite in this development given the strong similarities between sulfur based photosynthesis and respiration, i.e. swap hydrogen sulfide for water and S_2 for O_2 respectively for each reaction, but the energetic differences between these two reactions between sulfur and oxygen are large enough for this to be a significant barrier that was almost insurmountable for life taking over 2 billion years to happen. And moreover unlike other forms of respiration oxygen based respiration appears to have only evolved once since most microbes in anerobic environments appear to respire metals primarily Iron but you even have a number of microbes able to respire Uranium. As I learn more about the staggering diversity of anaerobic life compared to aerobic life I increasingly suspect it will eventually be found that metal respiration is the original form of respiration probably occurring originally in geothermal vents on the sea floor. Iron in particular is extremely effective for respiration among those reactions life has developed giving the second best energy per individual reaction after only oxygen. Iron also is cosmically highly abundant relative to other astrophysical metals and by far the most common atomic/chemical metal under typical conditions due to its extremely high Curie temperature allowing quantum mechanical properties to appear hundreds of kelvin above that of most other elements. It might even be found one day that life didn't arise in the ocean at all but rather below the ocean within seafloor rocks which incidentally seems to be the main reason why the abiotic requirement for a crystalline compound to be a mineral was dropped was the discovery that pretty much no rock in Earth's crust hasn't at some point been biologically processed, with many ore concentrations even being a consequence of ancient microbial metabolic activity. (Those banded Iron formations are literally a mass extinction locked in rocks) And we now know that the majority of Earth's water is below the Earth's crust in the mantle and core and have found life as deep down as we can drill so we can't even rule out deep abiogenesis which while it still seems to be implausible it is becoming less so. The Arxiv preprint for Prometheoarchaeum Syntrophicum www.biorxiv.org/content/10.1101/726976v2

[@ryan5769]

the eukaryote might even be much more composite than just one or two endosymbiotic events. mitochondria and plastids are obvious since they still have their own chromosomes, but most of their original DNA has migrated to the nucleus, keeping only what is beneficial to keep close for quick, finetuned behaviours in their metabolic processes. other organelles will have lost their chromosomes to the nucleus if they had no good reason to keep them close. eukaryotic flagella and other organelles may be endosymbiotic. then there's the hypothesis that the eukaryote's nucleus/chromosome layout is inherited from an endosymbiotic virus, as our chromosomes don't really resemble the circular ones of prokaryotes. this is called the viral eukaryogenesis hypothesis, really fascinating. I'd love to see a more speculative video about the possibilities here!

[@elijahmikhail4566]

ryan5769 We do know that it happened at least 4 times that we can confirm. The mitochondria and the chloroplasts obviously being the first occurrences. Then the secondary and tertiary endosymbiosis that drove the evolution of chromalveolates and dinoflagellates. So yeah, it might not be all that rare of an occurrence.

[@Phrenotopia]

@@Dragrath1 - I did hear of those Lokiarchaeotes but never dug into the topic until now. Truly fascinating to see these weird tentacular processes wrap around other microbes. They really look like alien microbes and are food for any later video I want to make on that topic!

[@thepip3599]

Woah, I was on the edge of my seat the whole time. It’s kinda funny how fascinated I was with stuff simpler than slime mold.

[@ObeyBunny]

This was the video that made me subscribe to your channel. You summarize early evolution perfectly, somehow striking just the sweetest spot between making your material easy enough for beginners to understand and detailed enough for viewers with higher proficiency to stay interested! Excellent work, Phrenotopia!

[@Phrenotopia]

Thank you so much, because that is exactly what I'm trying to achieve! For me this was born out of my frustration with both "discovery channel" level content going too slow, dwelling on "personal stories", while not giving profound enough understanding *and* academic level content that is too dense and presented in a boring "classroom" way.

[@tobyharrison4702]

This is one of the most interesting series I have found and considering I am probably going into paleontology this is very fascinating and fun to watch.

[@ajodea1191]

Hives and nests of eusocial animals are another layer of modularity - so...is a hive an organism?

[@Phrenotopia]

Yes, indeed it is!!! I wanted to mention that too, but left it out on the end, because I had already added so much. Something for a later video!

[@The_CGA]

Certainly there are some colonial species of byrozoans and stuff like Portuguese men-o-war that specialize at the unit of the **zooid**. There’s a recent discovery of epiphytic Ferns that appear to have a eusocial specialization in New Zealand that’s worth checking out

[@mysterylads3119]

This needs to have its own genre

[@alin2611]

Would it be possible for a large walking organism to be just a bunch of smaller animals working together as individual cells? Like a bunch of ants forming an amoeba like shape to be one giant organism (some acting as skin,some as a brain,sime as eyes,some digesting food,some acting like red blood cells delivering nutrients)

[@Phrenotopia]

In theory: Yes! And I'm already contemplating videos based on those premises.

[@Phrenotopia]

Siphonophores like the Portuguese-man-of-war are essentially colonies of animals of a single stock fused into a single entity. Modularity FTW!

[@alin2611]

@@Phrenotopia nice

[@animationspace8550]

@@Phrenotopia blue bottles are interesting.

[@Phrenotopia]

@@animationspace8550 What are blue bottles?

[@keithinadhd6693]

This was incredible. Thank you for making this. It laid out answers to questions I’ve had in a very through and entertaining way.

[@Phrenotopia]

Thank you! This may sound strange, but working with this topic and making it very concrete for myself alone with the visualizations that I created, also gave me a more profound understanding than I ever had before.

[@keithinadhd6693]

@Phrenotopia I can appreciate that. I especially liked your approach to explaining the details. Getting into the minutia like you did just made it all the better. They always say the best way to learn is teach.

[@Phrenotopia]

@@keithinadhd6693 - Yeah, people present things like cells often just as blobs, but there's so much more to them! They're like tiny robots with enormously complex processing going on inside in reality!

[@cerinlynx6119]

Man, I wish Spore was more like this

[@kamm6001]

Ah, a great video posted on my birthday! Thanks for all the help you're giving out to everyone.

[@novaraptorus6250]

Great video as always!

[@nzsantiago]

Love your videos! Love your style! Keep these coming please :) they're great!

[@mikelmikel988]

Hey how about you make and show us your speculative aliens

[@The_CGA]

I eagerly await your thoughts on how eukaryotic size challenges could be solved in a different manner and what evolutionary pressures might push prokaryote-analogues in this different directions. Check out Nick Lane’s arguments on how endosymbionts confer a specific advantage by localizing (and stabilizing, through competitive freezing of function) genetic information key to energy, thus freeing up the central “nucleus” director genome to focus on other stuff and grow larger (since it doesn’t have to spend all its time printing RNAs just to breathe)

[@Phrenotopia]

Thanks! I'll check it out!

[@NethanielShade]

I love the series man. Please keep it going!

[@petruraciula9056]

Aaaaand subscribed

[@worldbuildingjuice]

love your series! I wonder how sex for multicellular organisms evolved though. I'm not sure if you plan to talk about this later in the series or not, but if you do I guess i'll watch it soon. if not, maybe think about making a video like that. cheers! love the content!

[@taxivulpesia]

if we go off the 'inside-out' hypothesis for eukaryotic evolution, it makes sense for modular organisms to increase and grow!

[@michaeldeistung5907]

I hope you get more viewers! Great video

[@gorillabum4182]

The best channel on youtube so far

[@TripleA332]

Molecular plankton isn't real, he cant hurt you. Molecular plankton: 2:23

[@kurumachikuroe442]

Cells together strong

[@Iknowhowbadthisnameis8828]

Yes

[@kiyouestrada6222]

Thank you

[@elvd1296]

Did the magnetic field help designing of animals

[@animationspace8550]

It is used for some species to navigate like pigeons and turtles as far as I know. Though besides protecting us from dangerous uv rays and stripping the atmosphere, I don't know if it did much else.

[@kafrur]

Excellent!

[@kaigossen1339]

Most underrated shit ever

[@HECA758]

Hello,i am doing my own alien Planet biosphere,based in some videos and my own inagination.I want to know that how big is the chance that some new complex cell organism could exist in a alien planet based in a diet of Hidrogen Sulfide? ( Nice work btw) :3

[@rvoight92]

Check out the channel Biblaridion. He is also doing a speculative evolution series where a small percentage of the atmosphere is made up of hydrogen sulfide.

[@Shadowfolk369]

5:29 a system of cells interlinked within cells

[@danthiel8623]

Hello there

[@b0ark1ng21]

I love my cell

[@blaircolquhoun7780]

Life is complicated.

[@ohno6528]

Thrive

[@PedanticNo1]

Obligatory engagement comment. All hail the Algorithm.

[@b0ark1ng21]

Minecraft

[@neodintchly]

Me: I want Biblaridion's Alien Biosphere Mom: We have Alien Biosphere at home Alien Biosphere at home:

[@wormthirtyfour]

rude

[@neodintchly]

@@wormthirtyfour :')

[@animationspace8550]

@@neodintchly yeah man, that meme is more for things that are worse. This video is a bit more informative, while bib's are more creative and simple to perceive.

[@neodintchly]

@@animationspace8550 can't wait for Biblaridion's Alien Biosphere Anime

[@regularguy2807]

Second

[@cortoons7889]

First