It is such an interesting idea- deep evolution is only practically possible on small anatomical scales (likely enhanced by the capacity for adult organisms to produce vast numbers of tiny larvae to refine such changes). Has internal fertilisation of the more advanced vertebrates shut down this process? Early vertebrate embryos seem to now be under no more novel selective pressures that could drive the emergence of new variations on body plan. That suggests that fish would be the likely source of new innovations on this level, leaving the current terrestrial taxa as an evolutionary dead end given enough time.
I wouldn't go that far. The seeming "stagnation" of a lineage can be an illusion, as selective pressure encourages them not to change due to their high fitness. But evolution can also happen very quickly. Look at the extreme proliferation of homometabolous insects. Wings appeared pretty early in insect evolution, but metamorphosis was a later innovation.
@@LimeyLassen That is a great counter-example (though I believe many questions remain about the evolution of metamorphosis in insects). Amphibian metamorphosis is in the same category I suppose. But ultimately these examples seem to feature a delay in the appearance of the adult body plan so that the anatomically simple larvae can specialise in feeding. It doesnt represent the emergence of new body plans, just the delay in the development of old ones. The real test of my hypothesis would be in looking for any fish embryos that have altered body plans, but even there most of that process happens inside the protection of eggs, unlike more basal taxa where embryogenesis happens in the open water.
@@haldanebdoyle My impression is that revolutions happen after extinction events. Bats and whales both evolved at impressive speed after the K/T extinction. A blue whale only has the same "body plan" as its ancestors in a very loose sense.
@@LimeyLassen I acknowledge your point but think the basic embryological body plan of all vertebrates is highly uniform and under no direct selective pressure (especially when post embryonic variations from bats to whales are possible). The only functional adaptation I can think of is circular breathing in birds which allowed a much higher metabolic rate for flight, which is comparable to the shift from a single gut opening to two that allowed unidirectional flow of gut contents. The last deep change was the genome duplication that gave rise to the bony fishes, and I'm not sure that caused any fundamental embryological changes. Evolution of limbs was just a case of duplicating and specialising a few pre-existing morphology driving gene sets. I still suspect vertebrates are broadly incapable of the kind of changes that turned sponges into jellyfish into flatworms.
Cannot wait for the next video! I love this series so much! It coalesces hundred of hours of reading about the origins of complex life into a simple, intuitive animation you can watch at your convenience! My favorite thing to do when speculating about alien life is to focus on all the niches and forcing that these early organisms _could've_ faced and thus permanently and wildly changed even the most basic features of bilatarians as we know them!
always figured the deuterostome switch was during a sea squirt like stage. free swimming form lays on its back to gather falling detritus. if the gills are at the anus like in mollusks then switching the direction of flow eliminates fouling. when you switch back to a free swimming form the old bottom is the top due to having spent a few million years upside down. i wonder if the flounder will give rise to a whole multitude of sideways fish. Or neotenous tadpoles evolve into an eel analogue.
Wow, I spent months on a video on this subject. Now after watching this video it looks like garbage. 😂 I love this video, I can’t wait to see the vertebrate body plan evolution video! I am always amazed how much information you convey in such a simple way. Your videos have shaped my understanding of evolutionary biology, and I wanted to thank you for that.
Noooooo! Don't give up! You do you! Tbh I also often feel my videos end up as garbage but I keep on pushing through and so should you. 😄 The inner critic is one's greatest obstacle. And thanks for the kind words!
@@Phrenotopia Thank you! I wasn’t planning to give up just yet. I just realized how simple you could teach information such as this; in contrast to mine which kinda over complicates it. Your video on the evolution of the Arthropod body plan, inspired me to make my video. I loved seeing a detailed explanation on how arthropods evolved. Which is why I am *very* excited to see your vertebrate body plan video!
Love your step-by-step illustrations of hypothetical forms (along with showing animals today that STILL use those forms successfully). So clear and concise! Looking forward to the next one! Subscribed!
Super fascinating!!! I would definitely love to see a video explaining the transition from something like a worm to a Vertebrate/Fish. Always been interested in that, and that transition for me is specifically hard to conceive.
I'm currently reading "Across the Bridge" by Henry Gee. This video beautifully puts together many of the pieces that I have learned about in the book. I'll certainly watch your other videos. While Life is fascinating, it's more wonderful to learn how it became so.
I'm very interested in this topic and been eyeing this book for a while. I can't buy the physical version because of import taxes tho, and only could find the pdf version which is hard to read on my phone or kindle. Do you know if there's an ebook version of this? I'm not sure if the Amazon version is ebook or pdf as well
Excellent video! I'm looking forward to the next one. (I sent you an email a few days back, but I'm not sure if you got it. I have a couple of questions that would be out-of-place to ask here.)
The problem with this explanation is that it does not explain why the nervous system of chordates is structured differently, as well as the absence of transitional forms from the nervous system of worms to the nervous system of modern vertebrates.
I will talk about that in my next video. In fact, the nervous system of both vertebrates and arthropods are structured by analogue Hox genes so the main distinction is the location really...
Any thoughts on where ctenophora fits into this progression of grades? I understand it was assumed some time ago that they were closer to bilatarians due to their through-gut, but that they're now understood to represent a more basal branch than the cnidarians. There's even some molecular studies that suggest they're an even more basal branch of animals than sponges, having developed muscles and nerves independently of the parahoxazoa lineage. Awesome series. Can't wait for the video on vertebrates.
Yeah it's a bit of a hot mess right now. Molecular phylogenies can be a bit all over the place. I'm still betting they're nested near Cnidaria. The most astounding thing about Ctenophores is that they use different neurotransmitter molecules than other animals.
Excellent presentation, but the green-screen artifacts are a big distraction. Not sure how you are processing these, but this should be fixed with upcoming videos.
Not everyone is an expert in green screening, nor should they have to be in order to create informative content. Just enjoy the excellent presentation of material and try not to focus on the extraneous details.
Thank you for the compliment. Unfortunately, I don't have the luxury of setting up a studio in my tiny rental. I'm using Camtasia's background removal which is suboptimal, and I've tried and failed setting up a green screen. This is the best I can do for the time being, apart from moving furniture around...
YOU KNOW MORE THAN ME - your opinions on these other channel's research [The Logic of Biology - NanoRoom channel] & [talks by "Talk: How the Krebs cycle powers life and death - with Nick Lane" vid on Royal institute channel] showing how increased energy flow complexity in chemistry in a constrained volume region to not lose energy by thermal entropy leads to a self reflecting maintenance fractal entity=CELLS-life imho.
Phrenotopia I have a question on your video about Alternative Earths, near the end you mention habitable moons and that they would have enhanced protection from cosmic radiation but not the radiation from the host planet itself. So where does it come from, I'm guessing the star then it's reflected off the planet but I don't know.
Nope, it comes from the planet itself, and the moons in some extent. To have an Earth size or bigger moon, you need a big planet! A gas giant. Just look up the magnetospheres and radiation belts of our own giants in the solsys. Think about 2010: The Year We Make Contact. (IMO painfully underappreciated in the shadow of the original, which is one of the best movies if not the best that is ever made.) In our system the biggest one is Jupiter's, by far. The Van Allen belt looks like a joke in comparison "It is Jupiter’s combination of a strong magnetic field, Io’s prodigious source, and the magnetic coupling of charged particles to the planet’s rapid (10-hour) spin that drives the intense radiation. Jupiter’s magnetosphere is the largest structure in the solar system. Its size varies with fluctuations in the solar wind, but on average this magnetic bubble is around 12 million miles (20 million kilometers) wide. That’s about 150 times wider than the planet itself, and almost 15 times wider than the Sun. The Sun’s own wind of charged particles streams past Jupiter, stretching the planet’s magnetosphere into a tadpole shape. Its long tail reaches all the way to Saturn’s orbit - roughly twice as far from the Sun as Jupiter." You can also look up physics textbooks if you want a deeper understanding. And feel free to be nerdy and calculate everything as researchers do. (Of course you don't have to. _And I'm pretty sure neither Phrenotopia, nor any channel regular does._ 😉) I hope I could be of some help.
Of course, it all depends on details of the fictional system and it's position within its local cluster and its galaxy... That's when better understanding comes in handy if you want to go deeper. But not required in any way!
Great presentation. Most evolution occurred at the subcellular level as biochemistry and genetics. A new book published by Austin Macauley Publishers titled From Chemistry to Life on Earth outlines abiogenesis in great detail with a solution to the evolution of the genetic code and the ribosome as well as the cell in general using 290 references, 50 illustrations and several information tables with a proposed molecular natural selection formula with a worked example for ATP. The origin and evolution of the first protozoa is explained in detail in the chapter " On Past the Eukaryotes ".
Were multiple adult stages lost? Or evolved convergently over & over? Some genetic evidence suggests comb jellies may be older than sponges or cniderians.
Like I describe, multiple adult stages were lost to enable these subsequent phases. The ctenophores are an interesting case indeed and I need to give them more attention eventually.
If the mouth split into a mouth and an anus in protostomes by the sides of the blastopore folding together, then why isn’t this seen in protostome embryos today?
Excellent question! 👌🏼 The short answer is that ontogeny does not always necessarily reflect phylogeny (Haeckel's law is somewhat obsolete). The theory describes the formation of the through gut in adult forms, but once that occurred, different mechanisms for anus formation could have taken over. One of the few groups that still reflect this theory for through-gut formation in their development are polychaete annelids.
It is such an interesting idea- deep evolution is only practically possible on small anatomical scales (likely enhanced by the capacity for adult organisms to produce vast numbers of tiny larvae to refine such changes). Has internal fertilisation of the more advanced vertebrates shut down this process? Early vertebrate embryos seem to now be under no more novel selective pressures that could drive the emergence of new variations on body plan. That suggests that fish would be the likely source of new innovations on this level, leaving the current terrestrial taxa as an evolutionary dead end given enough time.
I wouldn't go that far. The seeming "stagnation" of a lineage can be an illusion, as selective pressure encourages them not to change due to their high fitness. But evolution can also happen very quickly. Look at the extreme proliferation of homometabolous insects. Wings appeared pretty early in insect evolution, but metamorphosis was a later innovation.
@@LimeyLassen That is a great counter-example (though I believe many questions remain about the evolution of metamorphosis in insects). Amphibian metamorphosis is in the same category I suppose. But ultimately these examples seem to feature a delay in the appearance of the adult body plan so that the anatomically simple larvae can specialise in feeding. It doesnt represent the emergence of new body plans, just the delay in the development of old ones. The real test of my hypothesis would be in looking for any fish embryos that have altered body plans, but even there most of that process happens inside the protection of eggs, unlike more basal taxa where embryogenesis happens in the open water.
@@haldanebdoyle My impression is that revolutions happen after extinction events. Bats and whales both evolved at impressive speed after the K/T extinction. A blue whale only has the same "body plan" as its ancestors in a very loose sense.
@@LimeyLassen I acknowledge your point but think the basic embryological body plan of all vertebrates is highly uniform and under no direct selective pressure (especially when post embryonic variations from bats to whales are possible). The only functional adaptation I can think of is circular breathing in birds which allowed a much higher metabolic rate for flight, which is comparable to the shift from a single gut opening to two that allowed unidirectional flow of gut contents. The last deep change was the genome duplication that gave rise to the bony fishes, and I'm not sure that caused any fundamental embryological changes. Evolution of limbs was just a case of duplicating and specialising a few pre-existing morphology driving gene sets. I still suspect vertebrates are broadly incapable of the kind of changes that turned sponges into jellyfish into flatworms.
Cannot wait for the next video!
I love this series so much! It coalesces hundred of hours of reading about the origins of complex life into a simple, intuitive animation you can watch at your convenience!
My favorite thing to do when speculating about alien life is to focus on all the niches and forcing that these early organisms _could've_ faced and thus permanently and wildly changed even the most basic features of bilatarians as we know them!
Oh man, so excited for the vertebrate recipe! This video was great and SUPER interesting, thank you so much for it!
Loved the clear description! Helped me fully grasp the concept!
Glad you liked it!
always figured the deuterostome switch was during a sea squirt like stage. free swimming form lays on its back to gather falling detritus. if the gills are at the anus like in mollusks then switching the direction of flow eliminates fouling. when you switch back to a free swimming form the old bottom is the top due to having spent a few million years upside down.
i wonder if the flounder will give rise to a whole multitude of sideways fish. Or neotenous tadpoles evolve into an eel analogue.
If you hadn't mentioned the flounder, I would have!
Interesting hypothesis! I know of one theory that posits that laying on the side appears to have led to the echinoderm body plan.
@@Phrenotopia are you suggesting that we may one day get a real….ahem….. star fish
@@Liethen Don't give me spec evo video ideas! 😉😉
Jellyfish get a bad rap.......I'm here for our Cnidarian cousins even if 650 million years separate us.
Wow, I spent months on a video on this subject. Now after watching this video it looks like garbage. 😂
I love this video, I can’t wait to see the vertebrate body plan evolution video! I am always amazed how much information you convey in such a simple way. Your videos have shaped my understanding of evolutionary biology, and I wanted to thank you for that.
Noooooo! Don't give up! You do you! Tbh I also often feel my videos end up as garbage but I keep on pushing through and so should you. 😄 The inner critic is one's greatest obstacle. And thanks for the kind words!
@@Phrenotopia Thank you! I wasn’t planning to give up just yet. I just realized how simple you could teach information such as this; in contrast to mine which kinda over complicates it.
Your video on the evolution of the Arthropod body plan, inspired me to make my video. I loved seeing a detailed explanation on how arthropods evolved. Which is why I am *very* excited to see your vertebrate body plan video!
Love your step-by-step illustrations of hypothetical forms (along with showing animals today that STILL use those forms successfully).
So clear and concise! Looking forward to the next one! Subscribed!
Thank you for the kind words!
Super fascinating!!! I would definitely love to see a video explaining the transition from something like a worm to a Vertebrate/Fish. Always been interested in that, and that transition for me is specifically hard to conceive.
Thank you! I'm working on that question right now 🙂
I'm currently reading "Across the Bridge" by Henry Gee. This video beautifully puts together many of the pieces that I have learned about in the book. I'll certainly watch your other videos. While Life is fascinating, it's more wonderful to learn how it became so.
I'm very interested in this topic and been eyeing this book for a while. I can't buy the physical version because of import taxes tho, and only could find the pdf version which is hard to read on my phone or kindle. Do you know if there's an ebook version of this? I'm not sure if the Amazon version is ebook or pdf as well
@@lumaaita8288 I got an epub on Kobo.
I love your videos and your (dutch?) accent.
You might want a plainer background when doing the greenscreen-style overlay though 🙂
Thanks and believe me I tried... I unfortunately don't have the luxury of a studio in my tiny rental 😞
Excellent video! I'm looking forward to the next one.
(I sent you an email a few days back, but I'm not sure if you got it. I have a couple of questions that would be out-of-place to ask here.)
But why does it take a Dutchman to explain so concisely in English the difference between protostomes & deuterostomes! Excellent vid; subscribed.
Kweenie! 😅
Right on. Thanks for sharing.
Your videos give fascinating insights in an understandable way for a non-biologist like me. Been watching for years. Thank you!
You're very welcome and thanks for watching!
Awesome
Very insightful. Love the content.
The problem with this explanation is that it does not explain why the nervous system of chordates is structured differently, as well as the absence of transitional forms from the nervous system of worms to the nervous system of modern vertebrates.
I will talk about that in my next video. In fact, the nervous system of both vertebrates and arthropods are structured by analogue Hox genes so the main distinction is the location really...
What an elegant theory, I must say!
Any thoughts on where ctenophora fits into this progression of grades? I understand it was assumed some time ago that they were closer to bilatarians due to their through-gut, but that they're now understood to represent a more basal branch than the cnidarians. There's even some molecular studies that suggest they're an even more basal branch of animals than sponges, having developed muscles and nerves independently of the parahoxazoa lineage.
Awesome series. Can't wait for the video on vertebrates.
Yeah it's a bit of a hot mess right now. Molecular phylogenies can be a bit all over the place. I'm still betting they're nested near Cnidaria. The most astounding thing about Ctenophores is that they use different neurotransmitter molecules than other animals.
Very concise video.
You have a talent for it.
Thank you for the kind words
Excellent presentation, but the green-screen artifacts are a big distraction. Not sure how you are processing these, but this should be fixed with upcoming videos.
At first, I thought there was a fan blowing his hair.
Not everyone is an expert in green screening, nor should they have to be in order to create informative content. Just enjoy the excellent presentation of material and try not to focus on the extraneous details.
Thank you for the compliment. Unfortunately, I don't have the luxury of setting up a studio in my tiny rental. I'm using Camtasia's background removal which is suboptimal, and I've tried and failed setting up a green screen. This is the best I can do for the time being, apart from moving furniture around...
merci
Cool
I have often wondered if tissue differentiation and cancer aren't, in origin, homologous.
YOU KNOW MORE THAN ME - your opinions on these other channel's research [The Logic of Biology - NanoRoom channel] & [talks by "Talk: How the Krebs cycle powers life and death - with Nick Lane" vid on Royal institute channel] showing how increased energy flow complexity in chemistry in a constrained volume region to not lose energy by thermal entropy leads to a self reflecting maintenance fractal entity=CELLS-life imho.
- th-cam.com/video/vBiIDwBOqQA/w-d-xo.html
Phrenotopia I have a question on your video about Alternative Earths, near the end you mention habitable moons and that they would have enhanced protection from cosmic radiation but not the radiation from the host planet itself. So where does it come from, I'm guessing the star then it's reflected off the planet but I don't know.
Nope, it comes from the planet itself, and the moons in some extent. To have an Earth size or bigger moon, you need a big planet! A gas giant. Just look up the magnetospheres and radiation belts of our own giants in the solsys.
Think about 2010: The Year We Make Contact. (IMO painfully underappreciated in the shadow of the original, which is one of the best movies if not the best that is ever made.)
In our system the biggest one is Jupiter's, by far. The Van Allen belt looks like a joke in comparison
"It is Jupiter’s combination of a strong magnetic field, Io’s prodigious source, and the magnetic coupling of charged particles to the planet’s rapid (10-hour) spin that drives the intense radiation.
Jupiter’s magnetosphere is the largest structure in the solar system. Its size varies with fluctuations in the solar wind, but on average this magnetic bubble is around 12 million miles (20 million kilometers) wide. That’s about 150 times wider than the planet itself, and almost 15 times wider than the Sun. The Sun’s own wind of charged particles streams past Jupiter, stretching the planet’s magnetosphere into a tadpole shape. Its long tail reaches all the way to Saturn’s orbit - roughly twice as far from the Sun as Jupiter."
You can also look up physics textbooks if you want a deeper understanding. And feel free to be nerdy and calculate everything as researchers do. (Of course you don't have to. _And I'm pretty sure neither Phrenotopia, nor any channel regular does._ 😉)
I hope I could be of some help.
Of course, it all depends on details of the fictional system and it's position within its local cluster and its galaxy...
That's when better understanding comes in handy if you want to go deeper.
But not required in any way!
@@4124V4TA-SNPCA-x thanks a lot for answering 👍
At first, I thought there was a fan blowing his hair.
Great presentation. Most evolution occurred at the subcellular level as biochemistry and genetics. A new book published by Austin Macauley Publishers titled From Chemistry to Life on Earth outlines abiogenesis in great detail with a solution to the evolution of the genetic code and the ribosome as well as the cell in general using 290 references, 50 illustrations and several information tables with a proposed molecular natural selection formula with a worked example for ATP. The origin and evolution of the first protozoa is explained in detail in the chapter " On Past the Eukaryotes ".
Fascinating! Thanks for the tip!
Were multiple adult stages lost? Or evolved convergently over & over? Some genetic evidence suggests comb jellies may be older than sponges or cniderians.
Like I describe, multiple adult stages were lost to enable these subsequent phases. The ctenophores are an interesting case indeed and I need to give them more attention eventually.
Your use of backside for dorsal jarred for a moment because in England "backside" is a word used for the buttocks! Great video though!
Whoops 🤭
I always wondered how a sponge became a fish
it wasn't necessarily a sponge but sponges and all other animals share an ancestor (a clump of cells like an advanced choanoflagellate colony).
If the mouth split into a mouth and an anus in protostomes by the sides of the blastopore folding together, then why isn’t this seen in protostome embryos today?
Excellent question! 👌🏼 The short answer is that ontogeny does not always necessarily reflect phylogeny (Haeckel's law is somewhat obsolete). The theory describes the formation of the through gut in adult forms, but once that occurred, different mechanisms for anus formation could have taken over. One of the few groups that still reflect this theory for through-gut formation in their development are polychaete annelids.
So did the first animals evolve out of plants or fungi? Or did they magically appear? You described how they changed!
Like I said they evolved from colonial choanoflagellates.
I believe plants, animals and fungi all branched out from a common ancestor.