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!
@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).
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.
@@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.
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.
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.
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.
@@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
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?
@@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.
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.
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
@@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.
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
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
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.
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.
@@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'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.
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
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.
@@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.
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.
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
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!
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.
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 RU-vid.
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
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.
@@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)
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.
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).
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
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.
" 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.
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 ❤
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.
Can I just say that I LOVE YOUR SEPTUM PIERCING! Thank you, PBS, for letting your staff express their individuality in ways most workplaces are arbitrarily against, it makes the content they appear in feel more authentic and shows how awesome of a place PBS probably is, to work at/for.
The incredible complexity of the topic matter wowed me. So cacbon dioxide is coupled to global temperature, and number of stomata is both coupled to CO2 concentration and temperature. But stomata amount is also related to water loss, which in turn must be controlled with respect to water gain, and THAT is then related to the evolution of powerful vascular systems. So in the Devonian there was barely any megaphylls, and if there were they were tiny. It was almost all Lycolytes with their microphylls. Decrease in the CO2 concentration came with corresponding drops in temperature, causing the Devonian-Cacboniferous ice ages, and so allowed megaphylls to not overheat, ALONG WITH vascular innovation allowing more stomata to be opened without the plant drying up. So, the Carboniferous is the age of megaphylls, with the spotlight shining on ferns. And, oh the CO2 decrease is caused by the land plants themselves, BUT not in the way you'd think. Instead it was a convoluted cause-and-effect chain involving roots breaking down barren mineral rocks starting from the Ordovician, and oceanic algea eating them, AND THEN it was the algea which actually absorbed the CO2. Props to Eons for somehow being able to express all this in about 10 minutes. Wow.
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
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.
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 !
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.
@@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.
@@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.
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.
@@RandomVidsforthoughtKinda ironic comment you’re making lol. It’s an endearing neurotic vibe this crew has but that’s exactly what makes this woman stands out with stronger presence for me. Don’t read too much hate into it
Tfw as a plant you not only provided the oceans with nutrients but also accidentally caused algal blooms and reduced oxygen levels that could've pressured some groups of lobe finned fish to adapt to their low-oxygen environments by starting to adapt to partially relying on atmospheric oxygen intake at the surface (Via gulping air).
@@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
Crazy to me that anyone rather believe traditional religions when people have discovered the information this channel explores… Not bagging on religion but the theory of evolution is so much greater.
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.
I find it ironic when people complain about human excesses toward the environment but give the plants a total pass. First they poisoned the air and water with corrosive oxygen, then later on, went crazy and locked away all the carbon from the atmosphere into giant deposits of coal and oil. Greedy plants don't care about the environment!
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.
A couple more years of global warming and we won't even have to watch RU-vid videos about these awesome plants, we'll just be able to walk outside and see 'em
"around 30 degrees Celsius in the early Devonian, which is twice as high as the current average." -- No, that's not how temperatures work. The scale doesn't start at zero (unless you're working in Kelvin).
