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- เผยแพร่เมื่อ 30 มิ.ย. 2024
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Plants first made their way onto land at least 470 million years ago but for their first 80 million years, leaves as we know them today didn’t exist. What held them back?
Thanks to Franz Anthony (franzanth.com) for the excellent reconstruction of early Devonian megaphyll leaves!
Produced by Complexly for PBS Digital Studios
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References: docs.google.com/document/d/18... - บันเทิง
Hi all! Around 5:30 we said "Average temperatures for the entire planet hovered around 30 degrees C in the early Devonian, which is twice as high as the current average," when we should've said, "Average temperatures for the entire planet hovered around 30 degrees C in the early Devonian, while today, they're around 15 C." Thanks to those who have pointed this out!
So... Why was the former a mistake?
You can put in the degree symbol using Alt+0176 as in 30° C.
@UCWWV3b8YSDXQweAeI5DMzbQ people were comparing it to absolute 0, so 30C isn't twice 15C when you compare to that. However it is twice as far from the freezing temperature of water at 1 Atmosphere, so they were still correct considering what they used as a measurement (C versus K).
@@AryadiSubagio Yes, isn't 30° C is twice as high as 15° C?
Understood
Yes, make a series about plant evolution!!!
Yeah
Yeah
Plsss
Botany!
And mashrum evolution
What really gets me is that there was a short period where forests existed but trees with megaphylls didn't yet. So you would just have giant, leafless plants. The middle Devonian is super weird and super underrated.
well the trees would have had microphyll leaves: so think of a modern conifer forest.
@@sophiejones3554 No, the Cladoxylopsids genuinely had no leaves. And then eventually evolved megaphylls to become the Progymnosperms and then eventually Gymnosperms. The Lycopsids however were trees with microphylls.
I would love to be able to visit a Devonian forest.
“The middle Devonian is super weird and super underrated.” Is just 👌 yes.
Lycopsid diversity had a huge headstart over that of the euphyllophytes. With the topic here being the rise of the megaphyll, it really can't emphasize the point that for tens of millions of years, lycopsids dominated the forest skylines from the upper Famennian stage to the mid Carboniferous. It could have very well been in excess of 40 million years. Around the time the first forests appear in the fossil record, lycopsids had a beyond significant majority of the vascular biodiversity over the combined monilophytes and progymnosperms.
It is hard for most people to conceive, because we have an aborescent view that is modern angiosperm and modern gymnosperm centric. To many people, those forests might as well be artists' conceptions of exoplanet life.
So, plants with big leaves are better at cooling off in hot environments. Is that part of the reason why conifers, which tend to grow in colder places, tend towards small needles instead?
More than likely
I think a study on why conifers tend to grow in colder regions would be interesting to read, or watch.
Conifers in tropical climates even have bigger leaves. The agathis genus has round angiosperm looking leaves....
Plants evolved leaves so that heat could leave.
It partly is to reduce surface area to prevent frezeing of water in the plant
Props to the paleobotanists for working this all out. And to eons for sharing it. And! Michelle for their awesome presentation (:
wait, Michelle uses they/them pronouns or you just don't want to assume?
It's a pleasure to listen to
@@selenaichtis6762 better safe than sorry
@@selenaichtis6762 Their isn't they or them. It's a possessive pronoun and is neutral in gender and isn't referring to Michelle, but to both Michelle and Eons.
@@selenaichtis6762 the first option.
I know it's slightly out of topic for this video, but fungi deserve a huge shout-out here! When it was mentioned that early plants didn't have roots that's because fungi were already on land providing that role. It was fungal networks of mycelium that broke down rocks, releasing those minerals for plants and producing the first soils together.
It was only when encountering areas where fungi weren't supplying the usual sustainence that it became evolutionarily advantageous for plants to develop their own root systems, mirroring those that the fungi provided. Even today it's more accurate to say that mycelium networks in forest floors are the farmers of the plants and trees above than it is to think of the plants as using the networks for transit. Both are true, but if the network decides to limit a particular tree's uptake there's not too many options it has to get around it. The network benefits from as many healthy partners as it can farm though, so will often do so only for the overall health of the forest, and only until there is once again enough to go around.
How the heck did we figure out that they do this?! Wow.
@@slwrabbits Science!
It's also worth noting that RuBisCo, a core enzyme of photosynthesis, has one of the worst enzymatic reaction rates of any enzyme known, and somewhere around 30°c starts running in reverse (binds O2 and cause a reaction chain that releases CO2). Standard 'C3' photosynthesising plants rely solely on it, whilst many desert and tropical plants use 'C4' photosynthesis or CAM photosynthesis to avoid RuBisCo's crapiness.
yes, very interesting point :)
It's also worth noting that while C4 and CAM have evolved multiple times, all known examples are recent evolution. Not hundreds of millions of years back.
@@petersmythe6462 I was wondering about that; my biochemistry course covered their existence but not their history.
@@IainG10 From my understanding they evolved alongside/as an arms race, with large grazers, so same period as they were evolving, but I"m not sure if that was really the connection, or if the drier environment of that time was what was spurring on both herbivores & grasses/c4's to evolve
If anybody has any book recommendations on this I would be really thankful
Let’s learn about grass next! I’ve always been interested in the fact that there was no grass on the ground until much later in time. And now it’s overtaking everywhere
Huh, I’ve never even thought about that, but it’s an excellent point and now I wanna hear about it as well. Was the ground just sand and mud?
@@griff4d7 there were ground cover plants. Part of what makes grass weird is that it is high silica (i believe) which makes it 'gritty' which makes it harder to digest and so has an advantage.
@@sarahgargani5836 Yes, it is difficult for herbivores to eat and digest it, so when early grasses began, they had an advantage in NOT being eaten as much. Then as they "gained ground" (Ah ha ha ha!) the herbivores had to evolve to EAT or go extinct. But by that time, grasses had a large head start. Now the herbivores that DO eat grasses can not sustain themselves on the NON grasses as well.
Poe’s law
@@isidoreaerys8745 don’t know what that is but cool
Please make another plant episode centered around ginkgo biloba trees and their unique "retro" leaf design!
it’s kinda wild to me that it’s the only species left of its entire order
Yeah I just planted 2 of them, hope I will see them big before I die, they were there before the dinosaurs and after my death. It somehow makes me happy
@@shadycactus6146 k
It's so interesting how every single thing is what it is for an specific reason, not because we wonder why things are different like leaves being different colors or why something grows somewhere only, it's amazing
So interesting. I’d love to see more content on prehistoric plants!
It always gets me how long live took to move onto land. Life on Earth = 4 Billion years. Life on Land = 470 Million years. That gap is just so enormous.
I'd love to see more vivid representations of how these eras changed things. Early plants making rocks into soil, how the first forests must have looked, to how plants and fruits may have looked way in the past.
When showing massive drops/increases in CO2 it would be wise to state exactly how long that took. I'm a teacher and if I put two graphs with wildly different scales on them a fairly high percentage of students will still make direct comparisons between them even if they are magnitudes of order off. Showing CO2 levels rapidly changing over millions of years without stating it is an invitation for less informed to think that it's comparable to the changes that we are currently making.
+
In the past change of 0.01 ppm CO2 per year was "fast". It accumulated over 10 of millions of years to create a huge drop or rise. Nowadays the change is 2-2.5 ppm per year
Less informed person reporting: Could you explain to me why said changes are not comparable?
I'd like to educate myself on the subject.
I'm also wondering about the causality between rising global average temperatures and increasing CO2 levels.
As a laymen i can't seem to find well documented research on the subject.
You're right, it's not comparable. The rate of CO2 change today is multiple orders of magnitude faster.
@@marcmorel7246 CO2 levels change 10 - 1,000 times slower in geologic time than they are currently changing, this is why it's not comparable and there would be no way to mistake an artificial process for a natural one.
CO2 can absorb outgoing long wave infrared radiation, thus effectively "trapping" its energy in the atmosphere instead of allowing it to escape to space. Since most CO2 is near the surface, increasing CO2 levels heat up the troposphere near the surface but cool the stratosphere (because there's less outgoing infrared to heat it).
Some might tell you that the absorption bands of CO2 (where its vibrations match infrared wave length) are saturated and thus increasing it wouldn't heat the atmosphere, but absorption bands become broader when there's more of a given molecule.
So each doubling of CO2 is less effective as the previous doubling but it still leads to more heat until the point whre Rayleigh scattering overwhelms the effect of any remaining band broadening and more CO2 would cool instead of warm the surface.
(That also means Venus's atmosphere is actually overdense and the planet would be hotter if it were thinner, interestingly enough).
I'm sorry for the following nitpick
2:30 light isn't converted into sugar; the energy captured from light is quintessential in stimulating the chemical process through which sugar is formed. It's just words of course, but there might be people that just don't know better and assume much more silly conclusions without an appropriate context (and I'm not even completely aware of the chemical elements involved in at least a few plants to be this much of an ass about this; right now I'm assuming there might be more than one variation of possible molecule recipes involved in the formation of, essentially, plant food).
Before avocado trees grow bark they have photosynthetic stems. Theyll also drop all their leaves if they get even a little stressed. I wonder if avocado revert to being more like an early plant when stressed
Uhh, what? o.O
I know that I do that when I'm stressed XD
No, they drop their leaves because they go into a "save resources" phase, maintaining the leaves could take too much energy. If they have a well established root system they can store energy for a fast recovery when the situation improves. Don't quote me though, I'm just applying common sense and have not done research on Avocado plants specifically.
One question I've had about plant evolution for a long time is how often different forms of photosynthesis convergently evolved in different plant taxa. There are three different methods of photosynthesis known today: C3, C4, and CAM, and all evolved in many unrelated groups of angiosperms at different points in history. So if multiple forms of photosynthesis have appeared so often in just the 66 million years of the Cenozoic, then did these forms also convergently evolve in gymnosperms during the Mesozoic? After all, gymnosperms filled many of the niches that angiosperms fill nowadays in environments where C4 or CAM photosynthesis are prevalent so it's hard to believe that they simply struggled with C3 in unfavorable environments for it at all times. The idea of C4 and CAM gymnosperms before angiosperms seems evolutionarly plausible and has always fascinated me, though I'm not certain how that can be proven through the fossil record.
Isoetes of today has CAM.
@@stefanostokatlidis4861 I think you are misinterpreting something by linking two seemingly similar facts together. C4 and CAM photosynthesis are adaptations for arid environments to prevent massive water loss and photorespiration. Neither of these photosynthesis methods occur in habitats with a reliable water supply, where the negative side effects of C3 photosynthesis are negated by the speed and low ATP cost to convert as much CO2 to glucose as fast and cheap as possible. Isoetes as a whole classification are restricted to watery habitats and are so primitive that they lack basic leaf anatomy that is fundamental to either C4 or CAM, so your claim is biologically impossible. I think you are mixing up the fact that isoetes have no stomata with the fact that CAM plants actively open and close their stomata based on the time of day and are concluding that the lack of air holes in a quillwort leaf must therefore make it a CAM photosynthesizer, which is simply not the case.
This is such an interesting question 😅 ADHD brain wants to desperately search for answers (it’s 1am heLp mEe!)
Super interesting topic. It's possible it might be one of em' ole unkowables though. Things we just... cannot know, idk tho
Or parasitic plants that lose photosynthesis altogether
PBS Eons is the best part of today's PBS neatly packed in a wonderful little channel. thank you!
Absolutely astounding, i love this series so much
We need more plant episodes!
leave them alone they're just trying to catch their breath
*Leaf
I would like it if you somehow chronologicalise all the ages & how they ended & their special features in a series. But that would be a huge undertaking i feel
Definitely something people study in school 😅 but would be v helpful
Pretty sure they did it. Or scieshow, one of those
@@emg508 link?
There are overview episodes on this in the back catalogue.
An episode on plant evolution and how they "trained" animals to work for them would be awesome!
I love that you make episodes about stuff I never would have thought about. I knew plants had stomata but how and why they came about and how they affected the Earth was a question I never thought to ask. I had paid so much attention to the changes they created by emitting oxygen as a by-product that other ways they modified the Earth kind of slipped by my consciousness. Thanks for this new window of exploration for me, I'm going to be busy finding more vids about this.
Hey, really excellent. I had a plant phys professor in the 70s tell us he thought that the carboniferous was an era of high carbon dioxide. I couldn’t agree with him because I (the entomology major) knew about the giant insects of this period and how they worked. This video finally puts it all together for me, thanks.
There really needs to be an episode discussing the late emergence of primary endosymbiosis that had led to eukaryotes. I'm personally a supporter of the oxtox model and would love to hear their thoughts.
Oh great! Now whenever someone says "Leaf me alone!" I'm gonna have to ask them, "What's stomata with you?"
I'd love to see a whole series just about ancient plants. Also I really enjoy your presentation style. Very laid back and pleasant. Still the best channel on TH-cam.
The Carboniferous Period really made big impact on everything. All that carbon being stored in those trees has had such a drastic effect on the whole world.
This was really cool, and well-explained, too! Thanks for what you do, Eons!
This presenter is absolutely phenomenal! I feel like she is telling me a story that I really want to pay attention to because of the enthusiasm she brings to the script. Just perfect! Thanks for your excellence!
Thank you for this excellent episode!
I would love to see a series on paleo botany. I'm very interested in what plants grew in each period, but there is not a lot of information available.
Microphylls are not limited in length by any means, but width. Many modern pine needles are effectively microphylls and lycophyte tree microphylls were very long
Thank you very much for providing this great explanatory presentation - I always wondered about these early plant forms!
Ok but the real question is what happened to Steve?
He fell
He got a job besides reading scripts on TH-cam
this is so interesting thank you guys so much for making these videos!!
Imagine if plants evolved to become mobile and sentient
They did. Their time scale is just so slow compared to our time scale that you do not notice their mobility or intelligence. 😁😁😁
now that is something cool
@@John77Doe not mobile but surprisingly Intelligent
just wait...
Thats us bro
Survey done! Keep up all your great work. We love it
I love this video. It scratches my brain so well. Thank you for this.
Gladly take the survey. Makes me feel considered and respected as a consumer
I was hoping this video would include how some plants, like cacti, lost or reduced eaves due to hot environments.
Her contributions to research are fascinating. I also love her as a host, and her personal style! Great addition to the team.
Bro I love his show so much, watch every single episode lol
could yall do a series on moss please :) i think that would be an interesting topic and people on youtube never really get into the deeper information on it
In his agony, the Colonel Kurtz whispered: "The humor... The humor..."
Wonderful infographics, video presentation and the style of presentation. Thank you!
In desert climates there's a Palo Verde tree. It has a green trunk and tiny leaves. I showed it to someone in Toronto where tree leaves are big. They asked if it was a dead tree. Mesquite has the same type of leaves.
I'd watch a series on plant evolution. Vote here if you want to as well.
And fungi!
stomatas be looking sus
What that stomata do?
yess please do more episodes on ancient plants and fungi every time you do it's amazing
After watching this videos, it leaves me more questions than answers. But surely it sheds a lot more light about natural history of plants. I hope this channel will grow even more informative in the future.
science does tend to do that.
the more you learn about something, the more you realize what you dont know
last time i was this early, land was covered in giant fungi
😂😂😂
The picture used to described the cocoloba tree is actually an image of the sea grape tree
Seagrape is a species of Coccoloba, not sure if they showed the right species with the 8ft leaves though.
Very nicely done! Thank you!
Awesome as always
Babe wake up a new pbs eons video just dropped
This was neat to learn. I'd like to know more about horticulture and botany from an evolutionary perspective.
This channel takes me back million years back every time I see their video. I always wanted to feel how the world would have been back then. Thank you so much for these videos and i get know more about evolution too ❤
thank god i have been waiting for a pbs eons upload
" So it was basically impossible for plants to produce large leafs until CO2 levels fell. "
If I understood correctly, they COULD have IF the temperature had been lower. Of course lower CO2 helps cooler temps (but earth could also have been cooler for other reasons). E.g. from my undertsanding, it's more the temperature, ultimately, that held back the larger leafs, even though those would have been useful for breathing.
Stating that a temperature was 'twice as high' only makes sense if you're working in Kelvins, twice the value in any other scale doesn't mean twice as much energy
Works in Rankine too
This is true from an absolute zero perspective, but 0C and 0F are also a measure of something. Twice as far from 0C would mean twice as much energy from freezing which is still a useful measure. Same with 0F although that is more abstract.
@@martinhogan9745 gotta ask.. what is twice as high as 0 C? Been pondering this for awhile
@@wadeinn463 If you are measuring from 0C the answer is 0C. If you are measuring from 0K, then it would be 273C. I was just saying that comparing percentages of temperature in measures other than a base in absolute 0 still mean something, they just have a relationship with something else (in C it is the freezing temperature of water at 1 Atmosphere)
I can't help but imagine traveling back in time to see our planet with very few plants and/or very different plants compared to today.
Thank you!
You guys should have Joey Santore from Crime Pays But Botany Doesn't do a guest appearance on plant evolution videos!
Wow this narrator has improved so much since the first time they were on
I almost feel bad for noticing that too :| I feel like they are a bit more comfortable or confident or something
@@ZedaZ80 lol, you're allowed to dislike someone's presentation skills
@@ZedaZ80 always remember if your criticizing someone to help their performance then your doing them a favor. that way they can work on improving
The narrator is nameless?
Her nose bling distracted from the verbiage.
Fantastic hosting. Great job!
I learned about this in my plant biology class! ☺️ so nice to see it in an eons video
Hold up a second. I thought that fungi made the first soils?
@@at1the1beginning wrong, at least according to this channel, they have a video about how fungi were the first to colonise the land, growing huge, tree like structures & breaking down rocks, well before plants had evolved the ability to leave the water
I would like a video on the evolution of plastids. I know that most organisms, including all plants and algae, ultimately acquired their plastids from the same endosymbiotic event. But evolution has made these diverge considerably over time, including the chlorophyll pigments used (and thus the color). More interestingly, the genus _Paulinella
_ and the species _ Pseudoblepharisma tenue_ both had unrelated endosymbiotic events in their histories, acquiring an unrelated cyanobacterium and a purple bacterium, respectively. Finally, the diatom family _Rhopalodiaceae_ has acquired non-photosynthetic cyanobacteria, though it's not clear what advantage they provide.
Amazing to imagine all this happening.
This video is a great example of how intricate and connected things are on our planet.. and other planets
It's always depressing seeing you make a perfect well organised essay on a topic every week when I can't write anything in more than 10 pages even if you give me 6 months.
Interesting topic as always !
Of course, it’s a whole team of people!
Unbe-LEAF-able. Then you told that dive bar joke. Please guys. Only one corny joke per enlightening and informative EONS episode. I just ate.
Beautiful presenter, great topic. Thanks!
The world of the late Silurian and early Devonian was crazy hot. Imagine how it would feel to experience that.
Also during the carboniferous age there weren't any organisms that could decompose or eat wood. Keeping the carbon in the soil.
Nowadays we have lots of fungi and animals that can eat it.
fungi evolved & took over land before wood did! This channel has another video on that
@@mehere8038 true before plants ruled the world there were fungi. The giant Prototaxus was one of them, I think.
@@mehere8038 I know.Fungi just didn't know how to digest wood. That's what I meant. Else the carboniferous age would not exist.
Their outfit is so cool!
love this channel everytime when i watch a video i learn something
I never knew that all these "nerdy" subjects as referred by some, are actually so interesting. Wow!
took the earth hundreds of millions of years to find a balance. took humans hundreds of years to off balance it all.
I miss steve
He'll be back when it's cooled off and he can unfurl his leaves again.
Great content again. Love this channel
8:00 I think is supposed to read: "until the temperature decreased" not: "CO2 levels fell". As large leaves are still very possible and likely, in high C02 environments
m Are plants sentient? We know they sense their environments to a significant degree; like animals, they can “see” light, as a New Scientist feature explains. They “live in a very tactile world,” have a sense of smell, respond to sound, and use taste to “sense danger and drought and even to recognize relatives
so probably yes, but we're too dumb to be able to confirm it
I am so puzzled by folks that deny evolution. There is so much evidence.
I think it takes a lot of practice to turn your brain off to that extent. They usually let slip very quickly that they don't know what evolution is; which probably helps.
I would like to see more about desertification, de-desertification and water management.
That was a super interesting talk.
Me looking at the leaves of the coccoloba tree pictured: idk they don't look that big
Conversion the corner: 2 meters is about 8 and a half feet long
Me: OH. OK. THEYRE BIGGER THAN PEOPLE. COOL. COOL COOL COOL COOL COOL
Michele is a great host. I want more episodes with them!
As someone who loves plants, this suits me the best
Great stuff!
Imagine a world with no green
Look up any paleo art of Archean Eon
Welcome to my world! I'm colour deficient, and what I'm told is green looks either brown, or in some cases blue, yellow or even red.
Wow
One thing I noticed here was a reference to *two* ice ages Unless the Early Ordovician ice age is counted as one of the two alongside the Late Paleozoic Ice age what was the second? Has there been work to demonstrated that all the ice melted at some point within the Late Paleozoic ice age?
Given the location of Gondwana as a vast but largely isolated polar continent I find that particularly unlikely as feedback effects from circulating currents blocking the intrusion of warmer air should have remained quite strong up through the Early stages of Pangaea when the more northern landmasses finally joined with Gondwana at the south pole.
All the work I have been able to find identifies only these two ice ages though they contained numerous interglacial episodes much like the Cenozoic Ice age even when the ice retreated poleward the planet should still have been in an ice age if any lasting ice cover was present at either pole. This is important since the conditions to initialize an ice age are fairly rare thus Occam's razor suggests there was likely a single ice age split into glacial maxima and minima as opposed to a brief punctuated episode of hot house conditions.
I absolutely LOVE LOVE LOVE this early period of earth's biology I can NOT get enough amazing video
Please don’t say the temperatures “were twice as high as the current average”! That only works for the Celsius scale. In Kelvin, a real doubling would be 300C!
Love the videos… they’re so well pitched.
It's biology and ecology, why would you use the Kelvin scale? Unless you're advocating in defense of Fahrenheit, which would be funny.
@@antoniousai1989 OP is right though? 30°C isn't "twice as high as" 15°C. You can only make a statement like this if on the scale you use zero actually means zero, which is the case for Kelvin but nor for °C and °F.
@@noradrenalin8062 in common life scenarios you use Celsius, not Kelvin.
@@antoniousai1989 Sure, but that is completly besides the point. "Half as hot" as 30°C is not 15°C, it's -111°C. The average temperature on earth today is not -111°C.
Omg they are backkkk 😍
This is becoming my favorite TH-cam channel
I would hugely appreciate videos or series of videos on what we know about the evolution of both land plants and animals. There are a lot of overlapping and even contradictory claims floating around there. And as sort of complete timescale would be nice to have for reference.
86C is not twice as high as 43C. It's more like 14% higher because 86 and 43C are actually 359 and 316K. Stop using proportions to describe temperature relationships unless you take into account the full temperature scale down to zero K.