Hey guys! I thought I should mention that yes, I kinda sorta stole this video idea from pbs eons haha, but this video is not meant to repeat what they've said or discredit their video in any way. I actually made this video because I felt like there was more to discuss on this topic and I hope that my video complements their video by providing additional background and information about the potential second purple earth event! So I hope you enjoy, and if you are interested in checking our pbs eons' video on purple earth I highly recommend it! -> ua-cam.com/video/IIA-k_bBcL0/v-deo.html
I don't watch PBS eons because of their overproduced videos that I find insufferable, so go on with pilfering ideas! You on the other hand, sound exactly like a university professor doing his/her slideshow. That's my way.
While PBS Eons covers a really broad range of material, for areas in your expertise (which happen to coincide with many of my interests) you add a lot more information and really thorough and clear explanations I do not see anywhere else. Thank you!
Hey Rachel, have there been any developments in research into abiogenesis in the last few years? Are we any closer to fleshing out a plausible mechanism? Would you give us a video on this if there is anything new to reveal please? 😊
So if I'm not mistaken then plants could be engineered to carry the bacteria rhodopsin too and made to look blackish instead to shades of other colours depending on the concentrations of these two light pigments in this dual system. If so then interesting.
Rachel, I'm a postdoc in geosciences (more specifically, in seismology) at Northwestern University, and found your channel less than a week ago. I'm absolutely amazed by the extremely high-quality content you have. I'll probably watch all of your videos! 😁 Your channel is, by far, the best I've ever seen on geosciences! Congratulations on the amazing work you have been doing by teaching so well! If you intend to become a professor (well, actually, you already are 😊), you will be an amazing one! Fortunately, now we have UA-cam to spread the kind of high-quality content such as yours to the four corners of the world! 😃
Wow this comment truely made my day! I do in fact plan on becoming a professor (for in person students haha). I actually have a postdoc position lined up at university of south carolina starting in the spring, and they are going to let me teach a course during my postdoc! :D Anyway, thank you so much for the kind words and encouragement! It means so much coming from a seismology doctor! ;) Best of luck with your postdoc and future endeavors!
Thanks! That's awesome! I'm sure you'll do great in your future postdoc 😄 Whenever my advisor is traveling, she asks me to teach in her place for a few days, which I always love :) But I didn't get the chance of teaching a whole course yet (although I may, early next year). Right now, I'm focusing on applying for a faculty position in geodynamics in Brazil (my home country). I found your channel precisely because I'm studying a lot. You explain really, really well 🙂 I wish you can keep the amazing job you're doing 😄 Good luck too!
Hey Caio! I was reading through my comments to find some good ones for a presentation, and just saw this! I am so glad we got to meet, but sad I couldn't get to see your poster presentation. You'll have to let me know what conference you are headed to next and maybe we can try again! ;D
born too early to live on a purple planet, too late to live on a purple planet, but just in time to be given a very informative video on when it was around. very cool of you, thank you!
Our body uses energy from the sun in the process of creating Vitamin D, I guess that would be phototrophy as well! Actually the history of the production of Vitamin D goes all the way back to early photosynthesizers, with the possibility that they made it as a sort of natural sunscreen to protect sensitive molecules inside. It's a bit of a rabbit hole itself haha
@@bramvanduijn8086 I was going to argue that it is, since we're diurnal, but I'm not sure if it would count lol. Or does it? Vitamin D is also essential for our immune systems, bone health, mental health, our intestines, etc. It still might not count, but my brain went there lol.
Apparently we used to make more than vitamin D too. When we started having a fruit based diet we were poisoning ourselves with too much vitamin B. So we lost the ability to make our own!
It is good you end up with astrobiology application. Reminding people geoscience goes beyond Earth and it is not a bad thing (geoscience) as many people thought.
Thank you for mentioning that we have retinal pigments in our eyeballs at around 11:48. I was getting confused why this purple pigment was called “retinal” until then. I had to look that up: It’s the light-sensitive compound that detect light in our eyes - hence “retina” - and our body produces it by breaking down Vitamin A. I was wondering what the connection to microbes was! I learned some biology today!
This stuff blows my mind. I wish more people knew about the early Earth. They didn't teach my kid this in school at all. I try to teach her this myself...
That is so amazing that you teach your daughter this stuff! I wish I was taught more of this stuff growing up. I myself am not an expert in teaching audiences younger than college age but I do think we should make an effort to provide at least some of this information in classes before college! Hopefully that will be the case in the future :)
"Where Did The Moon Come From? - Do We Really Need the Moon? - Preview - BBC Two" is a great video for students too. Theia was a planet of the size of Mars that was trapped in the same orbit of Earth. Gravity anomalies ended up making them to get close and collide. The early moon was way closer and looked, tides must have been tall, and Earth days lasted only 5 hours. Imagine the early Earth, a surface of molten radioactive lava, with a huge moon in a short day.
I like PBS eons but your videos are much more detailed then theirs and I actually feel like I understand the topic after watching your videos so thank you for making this.
Did a cursory search, and different methods of photosynthesis have arisen independently in bacteria quite a few times. Would enjoy seeing a video comparing their methods
Finally the UA-cam algorithm suggested this video. I am subscribing and looking forward to check your videos. This is really quality content and deserves more views. I love how passionate, yet composed, you are in the video. Best wishes to you, your loved ones and this channel, Erik.
Your channel plays a pivotal role in transforming people's understanding of nature and the world around us. It serves as a catalyst for the EVOLUTION of mental comprehension, contributing to a deeper and more enriched understanding of our surroundings. Thank you for fostering knowledge and enlightenment! On behalf of ALL of humanity, Thank You!!! ;o)
Point to note from a once-upon-a-time biophysics student: thermodynamics dictate that energy absorption by phototrophic organisms must ultimately be balanced by ability to radiate heat i.e. it has to run hotter to colder else there's no work to be done. Chlorophyllic life, by absorbing photon at the red and blue end of the spectrum, are optimally emitting waste heat using wavelengths at which our (oxygen enhanced) atmosphere is very transparent. The rhototans, in absorbing the mid-enrgy but most prevalent photons could only dump heat as reddish or blueish photons, neither of which traverse our (oxygen-enriched) atmosphere.
Such a great series of explanations Rachel. This is one of my favorite of your amazing series of videos. My Father in law is an early adopter of Photovoltaic energy capture. Next time I see him I'm going to mention that he is an ancient Phototroph 😆
Excellent video. You finally answered the question I’ve been having for years which is why plants reflect green when the solar spectrum peaks in green. Thank you!
Gold Star Geo Girl ; you've obviously been studying the ruminations of English philosopher and physicist John Locke. Well done on another great presentation Geo Girl !❤🎉
Very interesting about the reciprocity of absorption between the purple and green photosynthesises. Another insight into why photosynthetic pigment is green is in the paper “quieting a noisy antenna” by Trevor ARP, SCIENCE 26 Jun 2020 Vol 368, Issue 6498 pp. 1490-1495
i love how nerdy you are. Fun video! I always wondered why plants reflected green light instead of absorb it when we have a green star. now i know why!
Comment about info at 5:50-- I'm not Geogirl so it may be wrong! Phototaxis is when a whole organism moves toward the light. Phototropism (just one h) is when something turns toward the light, like Helianthus, the sunflower, and phototrophy (2 h's) is something getting energy from light. I love your channel!!
I feel like a teenager again, with a crush on Geo Girl. 🤣🤦♂😂💚🌍 Keep up the amazing work. Your quality shines through in the quality of these presentations. It's very inspiring.
If retinal-based phototrophs evolved first (based on wavelength spectrum absorption) and photosynthetic organisms later, then where did retinal-based phototrophs get their organic carbon from? Thank you
Great question! Before oxygenic photosynthesis evolved, there was already plenty of life, much of which was chemotrophic (got energy from chemicals rather than light), so the first phototrophs, whether they were these retinal based guys or something else, would've had plenty of org. carbon around :)
Thank you for your response! To clarify, are you suggesting that the sequence of events unfolded as follows: 4.1 billion years ago, the emergence of first chemotrophs (somewhere at oceanic floor next to hydrothermal vents); 3.7 billion years ago, the appearance of retinal-based phototrophs; and 3.5 billion years ago, the development of photosynthetic cyanobacteria, contributing to the formation of stromatolites?@@GEOGIRL
Wow, thank you for covering this topic. The metabolic diversity of prokaryotes is fascinating to me. I watched the eons video on this topic, but it left me feeling that I wanted more details, so this is exactly what I was hoping for. Also I feel like one time the channel it's okay to be smart did a video about purple sulfur bacteria but I can't for the life of me find it. So this was exactly what I needed.
Wow, this is super fascinating! I really appreciate these in-depth lecture-type videos on (astro)biology and geology, and I'm probably gonna spend the next few hours binging your videos! By the way, I'm the author of the purple planet image you used in your video and thumbnail. No worries though, because I actually feel pretty honored that a random 4-year-old SpaceEngine screenshot of mine made it into a UA-cam video of all things! Anyways, keep up the good work! :D
Not sure if it could be considered phototropy, but us humans do produce neurochemicals and vitamins from sunlight. So we are not that dissimilar to plants/phytoplankton. And yes, our eyes process sunlight better than our skin does. To be honest, I personally believe there is a correlation between the usage of UV blocking sunglasses and the rise in depression/anxiety disorders.
first of, first time watching and very interesting stuff (most of which i knew other than the fact the earth was once purple o_o)... secondly, I LOVE POWERPOINTS. also, no shame in taking ideas from PBS Eons - you have your own take and approach (and it seems lovely) - but they also have some of the best content. 😂
@@GEOGIRL I love it, it's great. I have a 40 yr interest in these topics. You're videos are addictive. I'll probably end up watching all of them within the next few weeks 🙂
Your aura, it's purple! You gotta find it fascinating that for all we have learned we still have so much more to learn. Stay curious. Thanks Rachel.. 👍👍👍
Great video, thanks! I appreciate the level of detail you go into. I'm a sucker for charts and figures. So purple earth occurred before the GOE, yes? If that's the case, then would earth's dull rocky landmasses be surrounded by a ring of purple shallows, with the oceans full of green iron sulfate? That would be a cool looking planet.
Haha yes, technically the land would've still been pretty bland, and earth would hardly have been fully purple. Rather it would've had the occasional purple 'bloom' or productivity lighting up the ocean's surface, but it still would've been so cool! ;D I imagine the Fe minerals would've been deeper rather than floating like planktonic blooms of phototrophs, so I would guess the purple was masking the green, but I could be wrong, especially since the ocean was probably not completely covered in these blooms. But idk, I am not sure how shallow the fe deposits would've come or if the more shallow regions would've been covered with carbonates like today (only abiotic instead of biotic ones). What an intriguing question! I will have to do more research ;)
@@GEOGIRL It seems to me this really emphasizes how complex it is to recognize life (or proto-life) on faraway planets. And even with we find it, there may be a lot of distance to anything that could lead to intelligent life. And if there is intelligent sulfur-based life, just how alien would it be to us?
Excellent. PBS Eons had a 10-min video on the same subject, Both are beautifully presented but this one goes into much more detail. "Complementary" (used later in the video) is a much better word than "opposite" to describe the different spectra,
It seems like animal life evolved from retinal based phototrophes because we still have retinals in our eyes, which may be a lagacy holdover from early evolution. If this is true, proto-animals switched over to resperation to take advantage of the oxygenation event. Perhaps study into mycology could shed light on this point, since fungi seem to resemble the hypothetical precursers to animal life.
An interesting excursion into a subject I know next to nothing about - thank you for enlightening me. One thing I’m slightly puzzled by at the moment (well, sort of two things): 1. Where did early retinal-based phototrophs get their organic carbon? (Which other organisms?) 2. Where did the first oxygenic photosynthesisers get their carbon dioxide?
Well the second is easiest, co2 was very abundant on early earth in both the atmosphere and oceans. The first question is less simple. The most simple answer is they got their org carbon from other early microbes, but what about the very first microbes? If we assume heterotrophs evolved first then where’d the first life get its organic carbon? Well there is actually organic carbon that is abiogenic (produced without needing life). These are not complex molecules, just simple amino acids, but none the less they are organic carbon that would’ve like fed the first heterotrophs on earth :) Also, like I mentioned in the video these early retinal guys might’ve been methanogens and thus could’ve gotten their carbon from methane :)
One of the few videos that I havent skipped ahead on because of some pointless chatter. Great job and I look forward to binging on the contents of your channel.
0:16: 🌍 The Earth may have been purple at some point in its history due to early photosynthetic organisms. 3:10: 🌱 Chlorophyll absorbs light in a region that is not the strongest output of the sun, while bacteria rhodopsin absorbs the opposite wavelengths. 6:29: 🌱 The absorption of light by different pigments in phototrophs and photosynthetic organisms results in different absorption properties. 9:57: 🌍 The evolution of phototrophs based on retinol and chlorophyll pigments suggests a co-evolutionary history in response to available wavelengths of light. 12:46: 🔬 Halo archaea may have evolved in anaerobic conditions and later developed the ability to use oxygen for metabolism. 15:58: 🌊 Low oxygen levels in some parts of the ocean and abundance of sulfide supported by sulfate-reducing bacteria and violet sulfur bacteria. 19:13: 🌱 The evolution of aquatic plants led to the development of non-vascular plants on land, which eventually allowed for the evolution of terrestrial animals. Recap by Tammy AI
I learned about this myself a decade ago, as a layman farmer. I noticed the nm gap for the solar peak and that was super counter intuitive to me. it didn't take much googling from that start point to stumble on this.
Chlorophyl maybe green but some plants change the spectrums they reflect vs absorb through other pigments such as anthocyanins, which can allow certain species of plants to become red, purple, or blue tinted.
I've seen research on plants' color and the rate of energy absorption across the spectrum suggesting that green is an evolutionary choice to forgo the intense, volatile middle of the spectrum and instead opt for the stability of red and blue wavelengths to generate more reliable output. It follows (or precedes) quite neatly that the first adopters would use a less efficient, higher risk/reward but more accessible chemical pathway and that the organisms we see are descendants and optimisers of that lottery's winners.
One question that I had while watching this video is why organism that use chlorophyll haven't since evolved different-pigmented chlorophyll that absorbs green light (after they out-competed retinal phototropes, leaving that absorption niche in the light spectrum open). If it's possible for red-and-blue-absorbing chlorophyll to evolve into green-absorbing chlorophyll (and the small yellow-wavelength absorption peaks of bacterial chlorophyll shown at 15:30 suggest it might be) , and that would be advantageous for the organisms that use it, it seems like 2.5 billion years must be enough time for that mutation to occur and spread. So maybe that means it's not actually advantageous then? Maybe red-and-green-absorbing chlorophyll is actually more optimal. Maybe the first photosynthetic organisms would have evolved to use that pigment of chlorophyll anyway, regards of whether green-absorbing retinal phototropes were dominant in the initial environment or not. I looked up that question on Quora (why chlorophyll doesn't absorb green), I noticed two points/claims answers people gave that might support that hypothesis: 1. In warmer climates, being able to reflect green light and therefore stay cooler may be an advantage to some photosynthetic organisms. 2. In practice, the amount of photosynthesis that organisms can perform is capped by things other than the amount of light they can absorb (the example of water availability was given), so theoretical organisms that used green-absorbing chlorophyll wouldn't be able to make use of the additional light they absorbed; they might just instead be able to absorb the same amount of light with fewer chlorophyll molecules. If anyone knows the answer, I'd love to hear it. Thanks!
@@GEOGIRL I always learn something new!!! I found this vid particularly interesting.. I believe this would also pertain to astro biology when posing the question of life on other planets pertaining to another Stars emission spectrum and what that could mean for possible life..Maybe we should be looking for Purple planets??? lol
Great video glad i found your channel 😍. Maybe the co2 levels had abit to do with the changes but the other thing certain light spectrums trigger growth characteristics in plants. In general, blue light spectrums encourage vegetative and structural growth and red light promotes flowering, fruit, leaf growth, and stem elongation.🤔
Wonderful presentation -- I hate to say it, but you and your Earth Pillow are adorable -- and you are brilliantly creative. Please keep up the good work. Your current and future students are fortunate to learn from you. Thanks.
10:30 this is interesting, because I heard different theory for this "inefficient" absorption of chlorophyll, and was on more popular channel, and was about overheating or something like this.
3:27 according to the data provided here Chlorophylle b actually seems spot on the wavelength of maximum solar output. Is there a reason you used this graph? Like, was the solar spectrum more like a K2V star before?
Thank you! I am so glad you appreciate that! Sometimes I wonder if I am sharing too much, like if there are certain unnecessary or boring details, but I just really like to make sure I share the whole story, so I am very glad you like that about my videos ;D
@@GEOGIRL Not at all. I find that there are tons of videos that do a high-level skim of the ideas, such as Eons. And those are fantastic videos, to be sure. But short of dry university lectures that happened to be caught on video, there is nearly no one giving additional detail. For a brief stint in grad school, when I was deconstructing my faith, I briefly embraced young-earth creationism precisely because the kinds of details you share were hard to access, leaving the door open to pseudo-scientists waving their hands and showing some niche examples that didn't fit the highest-level explanations. The details you share are extremely interesting to me. I LOVE it when you show graphs of it too. Too many STEM videos avoid the data or math to keep it accessible, but in doing so, they keep it appropriate for k-10. But I'm not going to take geology or biology courses at this point in my career, and I still want to learn this stuff, so your videos hit a very underserved segment in STEM science communication. Thanks!
Do you know how they got the hydrogen gradient on the original purple ones. If I remember right modern photosynthesis goes chlorophyll lenses create electric current then proteins use the electric current to do electrolysis to create a hydrogen gradient then the hydrogen gradients used by proteins to recharge ATP then sugar is bombarded by ATP and CO2 to make more sugar. I got the impression the second purple ones used hydrogen sulfide electrolysis instead of water electrolysis for a hydrogen gradient. So I'm curious what the first purple ones used as a hydrogen source for the hydrogen gradient for ATP?
That's a great question! I had to do some searching because I kept finding things that just said "the bacteriorhodospin undergoes structural change when it absorbs light which causes it to pump protons in/out of the cell" and I just kept being like "But where is it getting the protons?!" haha I finally found that bacteriorhodopsin-based phototrophs, like haloarchaea, take up protons directly from the surrounding environment, typically very saline & acidic water. This doesn't take any energy because when in a very saline/acidic environment, the hydrogen ions will already naturally want to go where they are less concentrated (into the cell). However, the cell then needs to pump them out of the cell to create the gradient of more out than in which drives the ATP synthase protein and thus, ATP production. This pumping the protons out of the cell requires energy because it goes against the natural concentration gradient of protons, so they use the energy from the light that their pigment's absorb to do this. I hope that helps! ;D And thanks for asking that, that is such an important question!
@@GEOGIRL So they get it from natural hydronium that enters through osmosis then fight the hydronium with light? Do you know where the acid comes from? I'm guessing it could come from carbonic acid but since the water is pretty salty salt would probably come with minerals which would turn into carbonate. Were there low levels of carbonate back then?
Great video with clear explanations. Does the evolution of different photosynthetic strategies have any relationship to the brightening of solar radiation over time? Solar luminosity was about 30% less intense when the Earth formed and has increased over time. Did early photosynthetic mechanisms need to capture more of the spectrum due to this lower intensity? Was the rise of chlorophyll-based mechanisms possible because more energy was later available at the upper and lower portions of the visible spectrum?
That's a great question! Based on how early in Earth's history both bactiorhodopsin and chlorophyll pigments evolved, I don't think the intensity had changed much by that time and thus, it likely did not play a large role in the evolution/properties of these pigments. Moreover, the solar spectrum has not changed over time, only the solar intensity, so I am not sure that would've affected the spectral properties of such pigments even if they had evolved much later. Like you said, they might've evolved to absorb more of the solar spectrum when it was less intense, and that seems to be the case with bacteriorhodopsin seemingly absorbing the more intense regions, but I am not sure if that is causation or correlation ;) Interesting thought though! :)
@@GEOGIRL thank you for your thoughtful reply. It is an interesting subject. I was around the Geology Department of the University of Tasmania (Australia) ca. 2005-2012 and there was some interesting research on the changing chemistry of the oceans during the Boring Billion, which turns out to be not boring at all.
Water absorbs lower frequencies of light faster than higher frequencies. (At 9 meters there is so little red light that blood appears to be blackish green because green and blue light are still available.) So chlorophyll's ability to absorb blue light would enable those organisms with it to undergo phototrophy at a deeper depth than the Retinol based organisms. And since the Retinol based organisms would view the Chlorophyll based organisms as "a source of organic carbon" that would come in very handy. Being able to absorb red light was just a convenient side effect because red just happens to be twice the wavelength of blue.
I am no expert in heliophysics, but from the little I know, we have reconstructed the sun's solar radiation history and it's intensity has been increasing over time but its emission spectrum has not changed. If there are any astronomers or alike out there who know more about this, please comment on this thread! This is such an interesting question, thanks for the comment! :)
@@GEOGIRL We all know life is dependent on the Sun on this Planet but since there has been a reconstructed solar radiation history created...I do believe the origin of life on this planets Giant purple elephant in the Room would be the Solar emissions spectrum and type of radiation and how that solar radiation was interacting with the first organic molecules on this planet.
Well yet another explanation why complex life evolved so late on Earth! Makes us wander if perhaps on other planets it could have met better conditions early on and evolved way earlier. So fascinating to imagine a Phanerozoic eon that is 2 billion years old or more instead of one just 540 million years old like it was the case on Earth!
Just came across this for the first time and this was fascinating. I'm an exoplanet atmosphere modeler but my office mate thinks about the Archean and I love trying to picture how incredibly bizarre Archean Earth must've looked. I've also heard it suggested that the skies would have been orange due to methane hazes, the land, such as there was, would've mostly been black due to the lack of oxidization or land based life, and the oceans might have been green due to all the dissolved unoxidized iron Is it right to imagine that the purple phototrophs would've mostly been in stromatolite colonies in shallow seas? So now basically I'm picturing a ocean world filled with green seas, dotted with black volcanic islands surrounded by purple lagoons, lit by orange smoggy skies?
I would say it is scientific consensus that it is one possible hypotheses regarding the early photosynthesizers, but it is certainly not the only one and it is also incredibly difficulty to say anything too certain about organisms that long ago, especially ones that were tiny and soft bodied, and thus do not have the best fossil record. So, yes, it is a real hypothesis backed by real evidence, but take it with a grain of salt considering there are other possibilities. :)
Hi Rachel! I've become a fan of your vids. You give lots of info. For example, I have always tried to find how dense were the Carboniferous forests. And you explain this in your video about this period. Please, make a vid about THE AZOLLA EVENT. Was it true or is it pure speculation? Can a single plant produce an extinction event in an era where there were lots of hervibores that could specialize to control it's expansion?
We love your knowledge. And it seams you have made a few trolls who publicly correct you for there own ideological needs. I say call them up and have a global lollipop. My 13 yo daughter is now buying her first electron microscope….an I say thank you.
Rachel, This video is the 💣! Tons of cell bio. Lipid bilayer. Membrane bound proteins. Retinal/rhodopsin vs. chlorophyll/PS1&2 💥. Red + blue = purple ✅.
Thanks so much! I am so glad you enjoyed it ;D It is one of my all time favs for sure! I just love talking about microbes, especially ancient microbes ;)
Rachel: What if Earth wasn't the only planet that experienced this purple phase? What if this hypothesis might give us insight into potential life on exoplanets…and if the purple earth hypothesis is correct and there was a dominance of purple organisms in the early Earth, then might we be able to find another planet that's at an earlier stage of evolution of the planet, where the purple pigments might have dominated?
Earth is not a planet. There are no planets, just round lights in the sky. We are down here... the sky is up there... the only thing purple is your brain. Get a new one.
Very good presentation. It is fascinating to hear about the molecules that has enabled our cells to manipulate energy (the source of life). In eukaryote cells mitochondria are the next evolutionary step on this path and pathology i mitochondria have been identified as the basis of many causes disease. Your hypothesis on the boring billion is interesting. I think the Black Sea has this kind of chemistry. The Black Sea being a fresh water lake before 7000 BC, became connected til the Mediterranean by earth quakes and salt water flowed into the lake. But fresh water kept coming from the great rivers keeping the Black Sea as a fresh water lake on the surface (200 m) and saltwater below the halocline. The chemistry of FeS makes the Black Sea black. It is also interesting that in the straits of Bosporus fresh water flows out at the surface, but saltwater flows in a a depth of 30-50 m, keeping the Black Sea salty.
This was really interesting. It seems like it could be an exciting field to work with if there are any examples of the older species left or able to be reproduced.
Couldn't it also be that green light photosynthesis developed in the green light in order for organisms not competing with *their own* retinal based phototrophy?
I am sorry, could you re-word the question? I am not sure I understand, I thought I tried to convey this point in the video so I want to make sure I understand what you are asking, thanks! :)
In my opinion there are two problems with the hypothesis: 1. Chemical analysis of the oldest rocks shows that the atmosphere of the early Earth was very inert and there wouldn't have been an abundant source of organic carbon on the 3.7 Ga which makes it more likely that the first phototrophs were producing vs consuming organic carbon. 2. Although the retinol based pigments absorb more light on the surface you have to remember that the first organisms lived in water and one of the chlorophyll absorbance peaks is in the blue light range (the wavelengths that can penetrate the furthest in water). This is going to be even more important on the early Earth when the top mixing layer of the oceans would have been inundated with intense UV light.
IIRC from my college biochem courses, oxygenic photosynthesis requires some free oxygen to get started. That's at least part of the reason anoxygenic photosynthesis started first.
Did oxygen photosynthesis need free oxygen to get started? Oxygenic photosynthesis is the photosynthetic production of free oxygen. Thus, oxygen is the product of this pathway, not the reactant. So, I am not sure it needed free oxygen to get started, but I could be wrong, there could certainly be very specific biochemical details I am unaware of :)
@@GEOGIRL I'm sorry, it's been a couple decades but like I said. If I recall correctly it takes a little bit of free oxygen to get it started. My information may be out of date because college was twenty years ago. But I'm pretty sure that at least one of the enzymes in the Calvin cycle needs free oxygen to form properly. Again this is from a lecture from twenty years ago so I may be out of date.
The sun has a peak in the number of photons that it emits at about 500 nm (599.6 Thz). The chlorophyll B absorbs light at about 475 nm (631 Thz). This "blue" light is more energetic than the "green" light. I am wondering if this difference might make sense based on quantum mechanics. The light is used to "kick" electrons up into a higher energy level. This can only happen if the energy of the light and the energy needed to kick the electrons up are identical. The difference in energy of the photons at the 500 nm and 475 nm is roughly 5%. The peak of sun light happening in the "green" part of the spectrum would suggest that plants would have evolved to be purple. The counter to this is that maybe the slightly higher energy "blue" photons can penetrate water better and have an energy that is closer to the specific energy needed to excite the electrons of the chlorophyll. This sounds like the makings of a good science experiment.
Is it possible to compete for particular spectra of light? Like, plants clearly compete for light, but it's a bit of an all-or-nothing game, isn't it? The green spectrum light wasn't passing directly through the retinol-based lifeforms, was it? Or is the implication here that they reflected enough light to enable the chlorophylls?
Where did the organic carbon reservoir come from, that was eaten by the heterotrophic retinal-based phototrops? Was there another type of autotrophic organic producing organism not yet based on chlorophyll around?
Fascinating. Always wondered why plants reflect reflect away the green part of the spectrum. So you say they choose a different part of the spectrum from the purple bacteria to be able to compete - by finding a different ecological niche, so to speak. But that is not so clear. It's not like purple bacteria use up all the purple in the world. Only makes sense if both kinds of bacteria are all bunched up together, literally living on top of each other and filtering the light that reaches those below. That is the implication of your theory. I would think each would stick to their own neighbourhood, where they are born, raised up, and die. In that case there is enough spectrum for all - at least until the plants killed off the purple bacteria by poisoning the atmosphere with oxygen.
Actually, it is for the exact reason you mention that this hypothesis is possible, it is that they did (and still do) live 'bunched up' or layered as you mention, in microbial mats! :) The green oxygenic phototrophs on top and the purple anoxygenic ones using the filtered light below. At least this is the case for oxygenic and anoxygenic photosynthesizers; I am not sure if it is also the case for the bacteriorhodspin-using phototrophs, but it is likely as the fossil record suggests that microbial mats were the major living 'behavior' of phototrophic microbes on this early earth :) But I wouldn't use the word 'choose' when explaining why green phototrophs evolved, but rather that this became the most beneficial and evolutionary advantageous trait (or pigment in this case) to have as a newly evolving phototroph in a world where you share space with the more primitive guys ;) Hope that makes more sense!
@@GEOGIRL Thanks for the clarification. An interesting analogy here are layered photocells for producing electricity from light. Each layer extracts energy from a different part of the spectrum, and allows the unused portion of the spectrum pass through to the layer beneath. In this manner they can max out the amount of energy that can be extracted from each square unit of surface.
Interesting about the eye absorbing light in retinal photosynthesis. The particular blue hue of the sky has a psychological effect on us giving us a feeling of well being. The lack of it for an extended time like winter periods gives some people today seasonal affective disorder (SAD) as an evolutionary adaptation. In the depths of winter in the ice age feeling like "seizing the day" and "making it all happen" by going outside in the freezing blizzard winds with no food, big game migrated away for the winter would likely mean a dead ice age man. Feeling like doing nothing is exactly the best strategy at such a time.
Hey guys! I thought I should mention that yes, I kinda sorta stole this video idea from pbs eons haha, but this video is not meant to repeat what they've said or discredit their video in any way. I actually made this video because I felt like there was more to discuss on this topic and I hope that my video complements their video by providing additional background and information about the potential second purple earth event! So I hope you enjoy, and if you are interested in checking our pbs eons' video on purple earth I highly recommend it! -> ua-cam.com/video/IIA-k_bBcL0/v-deo.html
I don't watch PBS eons because of their overproduced videos that I find insufferable, so go on with pilfering ideas! You on the other hand, sound exactly like a university professor doing his/her slideshow. That's my way.
While PBS Eons covers a really broad range of material, for areas in your expertise (which happen to coincide with many of my interests) you add a lot more information and really thorough and clear explanations I do not see anywhere else. Thank you!
Hey Rachel, have there been any developments in research into abiogenesis in the last few years? Are we any closer to fleshing out a plausible mechanism? Would you give us a video on this if there is anything new to reveal please? 😊
So if I'm not mistaken then plants could be engineered to carry the bacteria rhodopsin too and made to look blackish instead to shades of other colours depending on the concentrations of these two light pigments in this dual system. If so then interesting.
Beg pardon, but humans DO photosynthesize! (~6:00) We make Vitamin D using sunlight.
Rachel, I'm a postdoc in geosciences (more specifically, in seismology) at Northwestern University, and found your channel less than a week ago. I'm absolutely amazed by the extremely high-quality content you have. I'll probably watch all of your videos! 😁 Your channel is, by far, the best I've ever seen on geosciences! Congratulations on the amazing work you have been doing by teaching so well! If you intend to become a professor (well, actually, you already are 😊), you will be an amazing one! Fortunately, now we have UA-cam to spread the kind of high-quality content such as yours to the four corners of the world! 😃
Wow this comment truely made my day! I do in fact plan on becoming a professor (for in person students haha). I actually have a postdoc position lined up at university of south carolina starting in the spring, and they are going to let me teach a course during my postdoc! :D Anyway, thank you so much for the kind words and encouragement! It means so much coming from a seismology doctor! ;) Best of luck with your postdoc and future endeavors!
Thanks!
That's awesome! I'm sure you'll do great in your future postdoc 😄
Whenever my advisor is traveling, she asks me to teach in her place for a few days, which I always love :) But I didn't get the chance of teaching a whole course yet (although I may, early next year). Right now, I'm focusing on applying for a faculty position in geodynamics in Brazil (my home country). I found your channel precisely because I'm studying a lot. You explain really, really well 🙂 I wish you can keep the amazing job you're doing 😄 Good luck too!
Hey Caio! I was reading through my comments to find some good ones for a presentation, and just saw this! I am so glad we got to meet, but sad I couldn't get to see your poster presentation. You'll have to let me know what conference you are headed to next and maybe we can try again! ;D
born too early to live on a purple planet, too late to live on a purple planet, but just in time to be given a very informative video on when it was around. very cool of you, thank you!
Our body uses energy from the sun in the process of creating Vitamin D, I guess that would be phototrophy as well! Actually the history of the production of Vitamin D goes all the way back to early photosynthesizers, with the possibility that they made it as a sort of natural sunscreen to protect sensitive molecules inside. It's a bit of a rabbit hole itself haha
I don't know if it is phototrophic, since it doesn't give us a net increase in energy, but it is photosynthetic since it gives us vitamin D.
@@bramvanduijn8086 I was going to argue that it is, since we're diurnal, but I'm not sure if it would count lol. Or does it? Vitamin D is also essential for our immune systems, bone health, mental health, our intestines, etc. It still might not count, but my brain went there lol.
Apparently we used to make more than vitamin D too. When we started having a fruit based diet we were poisoning ourselves with too much vitamin B. So we lost the ability to make our own!
Also our retina converts light into chemical energy and then into action potentials, which is also phototrophic!
@@lolaby2 C.
It is good you end up with astrobiology application. Reminding people geoscience goes beyond Earth and it is not a bad thing (geoscience) as many people thought.
Earth 🌍 is not in a vacuum. . . Oh wait 😅
Dominion (2018)
@@Bostonceltics1369 My brain won't shut up lol.
Thank you for mentioning that we have retinal pigments in our eyeballs at around 11:48. I was getting confused why this purple pigment was called “retinal” until then. I had to look that up: It’s the light-sensitive compound that detect light in our eyes - hence “retina” - and our body produces it by breaking down Vitamin A. I was wondering what the connection to microbes was! I learned some biology today!
'Retinol' is the molecule
Dominion (2018)
Bilberry,puts the purple back in your eyes,OHH THE COLORS💜🤗💜😘👍
This stuff blows my mind. I wish more people knew about the early Earth. They didn't teach my kid this in school at all. I try to teach her this myself...
That is so amazing that you teach your daughter this stuff! I wish I was taught more of this stuff growing up. I myself am not an expert in teaching audiences younger than college age but I do think we should make an effort to provide at least some of this information in classes before college! Hopefully that will be the case in the future :)
"Where Did The Moon Come From? - Do We Really Need the Moon? - Preview - BBC Two" is a great video for students too. Theia was a planet of the size of Mars that was trapped in the same orbit of Earth. Gravity anomalies ended up making them to get close and collide. The early moon was way closer and looked, tides must have been tall, and Earth days lasted only 5 hours. Imagine the early Earth, a surface of molten radioactive lava, with a huge moon in a short day.
Same experience. Some of the information on hydrogen sulfide bacteria was in a bio textbook we used but we barely mentioned it in class.
I like PBS eons but your videos are much more detailed then theirs and I actually feel like I understand the topic after watching your videos so thank you for making this.
Did a cursory search, and different methods of photosynthesis have arisen independently in bacteria quite a few times. Would enjoy seeing a video comparing their methods
Me too
What an amazing communicator you are, you make everything so interesting!
Thank you so much! ;D
this channel deserves way more subscribers!!
Finally the UA-cam algorithm suggested this video. I am subscribing and looking forward to check your videos. This is really quality content and deserves more views. I love how passionate, yet composed, you are in the video. Best wishes to you, your loved ones and this channel, Erik.
Thank you so much for the kind words! 😊
Fascinating as always, keep the good work up if you can!
Your channel plays a pivotal role in transforming people's understanding of nature and the world around us. It serves as a catalyst for the EVOLUTION of mental comprehension, contributing to a deeper and more enriched understanding of our surroundings. Thank you for fostering knowledge and enlightenment! On behalf of ALL of humanity, Thank You!!! ;o)
Point to note from a once-upon-a-time biophysics student: thermodynamics dictate that energy absorption by phototrophic organisms must ultimately be balanced by ability to radiate heat i.e. it has to run hotter to colder else there's no work to be done. Chlorophyllic life, by absorbing photon at the red and blue end of the spectrum, are optimally emitting waste heat using wavelengths at which our (oxygen enhanced) atmosphere is very transparent. The rhototans, in absorbing the mid-enrgy but most prevalent photons could only dump heat as reddish or blueish photons, neither of which traverse our (oxygen-enriched) atmosphere.
Such a great series of explanations Rachel. This is one of my favorite of your amazing series of videos. My Father in law is an early adopter of Photovoltaic energy capture. Next time I see him I'm going to mention that he is an ancient Phototroph 😆
Thank you so much! I am so glad you enjoyed it, it is one of my favorites now as well :)
Excellent video. You finally answered the question I’ve been having for years which is why plants reflect green when the solar spectrum peaks in green. Thank you!
Gold Star Geo Girl ; you've obviously been studying the ruminations of English philosopher and physicist John Locke. Well done on another great presentation Geo Girl !❤🎉
🙏🙏🙏🙏 incredibly interested in early life… and the immense volume of earth time…. Blows my tiny mind…🙏
🙏
Very interesting about the reciprocity of absorption between the purple and green photosynthesises. Another insight into why photosynthetic pigment is green is in the paper “quieting a noisy antenna” by Trevor ARP, SCIENCE
26 Jun 2020 Vol 368, Issue 6498 pp. 1490-1495
Thank you for making this. Your channel is supes underrated. ^^
Thank you so much!
@@GEOGIRL You're most welcome :)
i love how nerdy you are. Fun video! I always wondered why plants reflected green light instead of absorb it when we have a green star. now i know why!
Brilliant video, new fan and checking out your others
Comment about info at 5:50-- I'm not Geogirl so it may be wrong! Phototaxis is when a whole organism moves toward the light. Phototropism (just one h) is when something turns toward the light, like Helianthus, the sunflower, and phototrophy (2 h's) is something getting energy from light. I love your channel!!
I feel like a teenager again, with a crush on Geo Girl. 🤣🤦♂😂💚🌍
Keep up the amazing work.
Your quality shines through in the quality of these presentations. It's very inspiring.
Thank you so much! So glad you enjoy the videos :)
If retinal-based phototrophs evolved first (based on wavelength spectrum absorption) and photosynthetic organisms later, then where did retinal-based phototrophs get their organic carbon from?
Thank you
Great question! Before oxygenic photosynthesis evolved, there was already plenty of life, much of which was chemotrophic (got energy from chemicals rather than light), so the first phototrophs, whether they were these retinal based guys or something else, would've had plenty of org. carbon around :)
Thank you for your response! To clarify, are you suggesting that the sequence of events unfolded as follows: 4.1 billion years ago, the emergence of first chemotrophs (somewhere at oceanic floor next to hydrothermal vents); 3.7 billion years ago, the appearance of retinal-based phototrophs; and 3.5 billion years ago, the development of photosynthetic cyanobacteria, contributing to the formation of stromatolites?@@GEOGIRL
Beautiful! Good Sunday!
Thank you! ;D
Wow, thank you for covering this topic. The metabolic diversity of prokaryotes is fascinating to me. I watched the eons video on this topic, but it left me feeling that I wanted more details, so this is exactly what I was hoping for. Also I feel like one time the channel it's okay to be smart did a video about purple sulfur bacteria but I can't for the life of me find it. So this was exactly what I needed.
Just discovered this page & I immediately hit the subscribe button. Looking forward to watching all the videos, past & future. 🤗
Thanks so much! So glad you like my videos ;D
so cool🦠💜🌎 great videos! thank you for all your time and efforts🍎
Wow, this is super fascinating! I really appreciate these in-depth lecture-type videos on (astro)biology and geology, and I'm probably gonna spend the next few hours binging your videos!
By the way, I'm the author of the purple planet image you used in your video and thumbnail. No worries though, because I actually feel pretty honored that a random 4-year-old SpaceEngine screenshot of mine made it into a UA-cam video of all things! Anyways, keep up the good work! :D
Wow thank you so much! And thanks for letting me use your image it is so beautiful!!🤩
I am so glad you liked the video 😊
I never had any special affinity towards geology, but I like this channel. Subbed!
wow, this was so fun to watch. this video has unlocked so many new things for me to learn about that i didn't know of at all. really cool!
Not sure if it could be considered phototropy, but us humans do produce neurochemicals and vitamins from sunlight. So we are not that dissimilar to plants/phytoplankton. And yes, our eyes process sunlight better than our skin does. To be honest, I personally believe there is a correlation between the usage of UV blocking sunglasses and the rise in depression/anxiety disorders.
I had never heard of this before. It is interesting!
first of, first time watching and very interesting stuff (most of which i knew other than the fact the earth was once purple o_o)... secondly, I LOVE POWERPOINTS. also, no shame in taking ideas from PBS Eons - you have your own take and approach (and it seems lovely) - but they also have some of the best content. 😂
this is an amazing channel. the website linked is great too ! V glad the algorithm recommended this channel for me
Thanks so much! So glad you like my channel ;D
@@GEOGIRL I love it, it's great. I have a 40 yr interest in these topics. You're videos are addictive. I'll probably end up watching all of them within the next few weeks 🙂
Your aura, it's purple! You gotta find it fascinating that for all we have learned we still have so much more to learn. Stay curious. Thanks Rachel.. 👍👍👍
Thank you so much! And yes, I am always amazed at how much we still have to learned, but it also makes me so excited to do so ;D
My fantasy world has mostly purple/violet vegetation for other reasons, but this is very...convenient. Thank you.
Great video, thanks! I appreciate the level of detail you go into. I'm a sucker for charts and figures.
So purple earth occurred before the GOE, yes? If that's the case, then would earth's dull rocky landmasses be surrounded by a ring of purple shallows, with the oceans full of green iron sulfate? That would be a cool looking planet.
Haha yes, technically the land would've still been pretty bland, and earth would hardly have been fully purple. Rather it would've had the occasional purple 'bloom' or productivity lighting up the ocean's surface, but it still would've been so cool! ;D I imagine the Fe minerals would've been deeper rather than floating like planktonic blooms of phototrophs, so I would guess the purple was masking the green, but I could be wrong, especially since the ocean was probably not completely covered in these blooms. But idk, I am not sure how shallow the fe deposits would've come or if the more shallow regions would've been covered with carbonates like today (only abiotic instead of biotic ones). What an intriguing question! I will have to do more research ;)
@@GEOGIRL It seems to me this really emphasizes how complex it is to recognize life (or proto-life) on faraway planets. And even with we find it, there may be a lot of distance to anything that could lead to intelligent life. And if there is intelligent sulfur-based life, just how alien would it be to us?
New discovery about past earth history thank you geo girl excellent
Excellent. PBS Eons had a 10-min video on the same subject, Both are beautifully presented but this one goes into much more detail. "Complementary" (used later in the video) is a much better word than "opposite" to describe the different spectra,
It seems like animal life evolved from retinal based phototrophes because we still have retinals in our eyes, which may be a lagacy holdover from early evolution. If this is true, proto-animals switched over to resperation to take advantage of the oxygenation event. Perhaps study into mycology could shed light on this point, since fungi seem to resemble the hypothetical precursers to animal life.
New to you, delighted, subscribed
As always thank you for your vids in which you are going deeper into subjects I've only been hearing about superficially but that interest me greatly~
Thanks so much! So glad you liked the deep dive ;)
An interesting excursion into a subject I know next to nothing about - thank you for enlightening me. One thing I’m slightly puzzled by at the moment (well, sort of two things): 1. Where did early retinal-based phototrophs get their organic carbon? (Which other organisms?) 2. Where did the first oxygenic photosynthesisers get their carbon dioxide?
Well the second is easiest, co2 was very abundant on early earth in both the atmosphere and oceans. The first question is less simple. The most simple answer is they got their org carbon from other early microbes, but what about the very first microbes? If we assume heterotrophs evolved first then where’d the first life get its organic carbon? Well there is actually organic carbon that is abiogenic (produced without needing life). These are not complex molecules, just simple amino acids, but none the less they are organic carbon that would’ve like fed the first heterotrophs on earth :) Also, like I mentioned in the video these early retinal guys might’ve been methanogens and thus could’ve gotten their carbon from methane :)
Thank you,@@GEOGIRL, for your quick answer to my questions!
I just discovered your channel, and I really appreciate that you provide all your references. Many thanks to you!
Thank you! So glad you enjoy my content ;D
One of the few videos that I havent skipped ahead on because of some pointless chatter. Great job and I look forward to binging on the contents of your channel.
0:16: 🌍 The Earth may have been purple at some point in its history due to early photosynthetic organisms.
3:10: 🌱 Chlorophyll absorbs light in a region that is not the strongest output of the sun, while bacteria rhodopsin absorbs the opposite wavelengths.
6:29: 🌱 The absorption of light by different pigments in phototrophs and photosynthetic organisms results in different absorption properties.
9:57: 🌍 The evolution of phototrophs based on retinol and chlorophyll pigments suggests a co-evolutionary history in response to available wavelengths of light.
12:46: 🔬 Halo archaea may have evolved in anaerobic conditions and later developed the ability to use oxygen for metabolism.
15:58: 🌊 Low oxygen levels in some parts of the ocean and abundance of sulfide supported by sulfate-reducing bacteria and violet sulfur bacteria.
19:13: 🌱 The evolution of aquatic plants led to the development of non-vascular plants on land, which eventually allowed for the evolution of terrestrial animals.
Recap by Tammy AI
I learned about this myself a decade ago, as a layman farmer. I noticed the nm gap for the solar peak and that was super counter intuitive to me. it didn't take much googling from that start point to stumble on this.
As a live-long lover of purple things, this is exciting to learn about. Great video; thanks!
Oops, *life-long.
Also: bunch of great content here. Subbed!
Chlorophyl maybe green but some plants change the spectrums they reflect vs absorb through other pigments such as anthocyanins, which can allow certain species of plants to become red, purple, or blue tinted.
Really fascinating stuff! Thank you so much.⚗⚛🔬🌌☄
I've seen research on plants' color and the rate of energy absorption across the spectrum suggesting that green is an evolutionary choice to forgo the intense, volatile middle of the spectrum and instead opt for the stability of red and blue wavelengths to generate more reliable output. It follows (or precedes) quite neatly that the first adopters would use a less efficient, higher risk/reward but more accessible chemical pathway and that the organisms we see are descendants and optimisers of that lottery's winners.
This is what I have seen too. It’s a compromise - avoiding getting “sunburnt” as it were - from absorbing too much radiation.
One question that I had while watching this video is why organism that use chlorophyll haven't since evolved different-pigmented chlorophyll that absorbs green light (after they out-competed retinal phototropes, leaving that absorption niche in the light spectrum open). If it's possible for red-and-blue-absorbing chlorophyll to evolve into green-absorbing chlorophyll (and the small yellow-wavelength absorption peaks of bacterial chlorophyll shown at 15:30 suggest it might be) , and that would be advantageous for the organisms that use it, it seems like 2.5 billion years must be enough time for that mutation to occur and spread.
So maybe that means it's not actually advantageous then? Maybe red-and-green-absorbing chlorophyll is actually more optimal. Maybe the first photosynthetic organisms would have evolved to use that pigment of chlorophyll anyway, regards of whether green-absorbing retinal phototropes were dominant in the initial environment or not.
I looked up that question on Quora (why chlorophyll doesn't absorb green), I noticed two points/claims answers people gave that might support that hypothesis:
1. In warmer climates, being able to reflect green light and therefore stay cooler may be an advantage to some photosynthetic organisms.
2. In practice, the amount of photosynthesis that organisms can perform is capped by things other than the amount of light they can absorb (the example of water availability was given), so theoretical organisms that used green-absorbing chlorophyll wouldn't be able to make use of the additional light they absorbed; they might just instead be able to absorb the same amount of light with fewer chlorophyll molecules.
If anyone knows the answer, I'd love to hear it. Thanks!
I love it when Jackson's chameleons change color, and now I can say the same about the Earth. 😊 ❤
Always Enlightening Information!!! I would have never thought the Earth was once possibly Purple!!!
Thank you! So glad you enjoyed it and learned something new ;D
@@GEOGIRL I always learn something new!!! I found this vid particularly interesting.. I believe this would also pertain to astro biology when posing the question of life on other planets pertaining to another Stars emission spectrum and what that could mean for possible life..Maybe we should be looking for Purple planets??? lol
Great video glad i found your channel 😍. Maybe the co2 levels had abit to do with the changes but the other thing certain light spectrums trigger growth characteristics in plants. In general, blue light spectrums encourage vegetative and structural growth and red light promotes flowering, fruit, leaf growth, and stem elongation.🤔
Wonderful presentation -- I hate to say it, but you and your Earth Pillow are adorable -- and you are brilliantly creative. Please keep up the good work. Your current and future students are fortunate to learn from you. Thanks.
She's a brilliant liar and fool... maybe she should get out of "science" and back to the kitchen ... recipes can be very creative.
Both very interesting and explanatory!
Well done , ( This really needs to be included in school bio classes , big time)
People also absorb solar energy, to make certain vitamine, enzymen etc. This helps us to energizer our system to make atp too
10:30 this is interesting, because I heard different theory for this "inefficient" absorption of chlorophyll, and was on more popular channel, and was about overheating or something like this.
3:27 according to the data provided here Chlorophylle b actually seems spot on the wavelength of maximum solar output. Is there a reason you used this graph? Like, was the solar spectrum more like a K2V star before?
12:25 dose solar spectrum change with time? Because Sun is not same as it was, but I don't know about light spectrum.
I always appreciate that you add the "how do we know" parts in more detail than other videos.
Thank you! I am so glad you appreciate that! Sometimes I wonder if I am sharing too much, like if there are certain unnecessary or boring details, but I just really like to make sure I share the whole story, so I am very glad you like that about my videos ;D
@@GEOGIRL Not at all. I find that there are tons of videos that do a high-level skim of the ideas, such as Eons. And those are fantastic videos, to be sure. But short of dry university lectures that happened to be caught on video, there is nearly no one giving additional detail.
For a brief stint in grad school, when I was deconstructing my faith, I briefly embraced young-earth creationism precisely because the kinds of details you share were hard to access, leaving the door open to pseudo-scientists waving their hands and showing some niche examples that didn't fit the highest-level explanations.
The details you share are extremely interesting to me. I LOVE it when you show graphs of it too. Too many STEM videos avoid the data or math to keep it accessible, but in doing so, they keep it appropriate for k-10. But I'm not going to take geology or biology courses at this point in my career, and I still want to learn this stuff, so your videos hit a very underserved segment in STEM science communication.
Thanks!
Do you know how they got the hydrogen gradient on the original purple ones. If I remember right modern photosynthesis goes chlorophyll lenses create electric current then proteins use the electric current to do electrolysis to create a hydrogen gradient then the hydrogen gradients used by proteins to recharge ATP then sugar is bombarded by ATP and CO2 to make more sugar. I got the impression the second purple ones used hydrogen sulfide electrolysis instead of water electrolysis for a hydrogen gradient. So I'm curious what the first purple ones used as a hydrogen source for the hydrogen gradient for ATP?
That's a great question! I had to do some searching because I kept finding things that just said "the bacteriorhodospin undergoes structural change when it absorbs light which causes it to pump protons in/out of the cell" and I just kept being like "But where is it getting the protons?!" haha I finally found that bacteriorhodopsin-based phototrophs, like haloarchaea, take up protons directly from the surrounding environment, typically very saline & acidic water. This doesn't take any energy because when in a very saline/acidic environment, the hydrogen ions will already naturally want to go where they are less concentrated (into the cell). However, the cell then needs to pump them out of the cell to create the gradient of more out than in which drives the ATP synthase protein and thus, ATP production. This pumping the protons out of the cell requires energy because it goes against the natural concentration gradient of protons, so they use the energy from the light that their pigment's absorb to do this. I hope that helps! ;D And thanks for asking that, that is such an important question!
@@GEOGIRL So they get it from natural hydronium that enters through osmosis then fight the hydronium with light? Do you know where the acid comes from? I'm guessing it could come from carbonic acid but since the water is pretty salty salt would probably come with minerals which would turn into carbonate. Were there low levels of carbonate back then?
Great video with clear explanations. Does the evolution of different photosynthetic strategies have any relationship to the brightening of solar radiation over time? Solar luminosity was about 30% less intense when the Earth formed and has increased over time. Did early photosynthetic mechanisms need to capture more of the spectrum due to this lower intensity? Was the rise of chlorophyll-based mechanisms possible because more energy was later available at the upper and lower portions of the visible spectrum?
That's a great question! Based on how early in Earth's history both bactiorhodopsin and chlorophyll pigments evolved, I don't think the intensity had changed much by that time and thus, it likely did not play a large role in the evolution/properties of these pigments. Moreover, the solar spectrum has not changed over time, only the solar intensity, so I am not sure that would've affected the spectral properties of such pigments even if they had evolved much later. Like you said, they might've evolved to absorb more of the solar spectrum when it was less intense, and that seems to be the case with bacteriorhodopsin seemingly absorbing the more intense regions, but I am not sure if that is causation or correlation ;) Interesting thought though! :)
@@GEOGIRL thank you for your thoughtful reply. It is an interesting subject. I was around the Geology Department of the University of Tasmania (Australia) ca. 2005-2012 and there was some interesting research on the changing chemistry of the oceans during the Boring Billion, which turns out to be not boring at all.
@@robertmoye7565 Agreed! The boring billion had some of the most interesting ocean chemistry ever! That is actually right up my research ally ;)
I would love to know what programs you use to make these presentations?
Haha, I am pretty 'low tech' ;) I just use powerpoint for my lecture slides and zoom for recording :)
@GEOGIRL Thank you for replying, much appreciated. I'll look into Zoom
💧☀️🌍💚
Water absorbs lower frequencies of light faster than higher frequencies.
(At 9 meters there is so little red light that blood appears to be blackish green because green and blue light are still available.)
So chlorophyll's ability to absorb blue light would enable those organisms with it to undergo phototrophy at a deeper depth than the Retinol based organisms.
And since the Retinol based organisms would view the Chlorophyll based organisms as "a source of organic carbon" that would come in very handy.
Being able to absorb red light was just a convenient side effect because red just happens to be twice the wavelength of blue.
I have learned a lot. Thanks!
@10:24 Is it possible when this was all occurring the Sun was actually producing more of the different wave lengths of light?
I am no expert in heliophysics, but from the little I know, we have reconstructed the sun's solar radiation history and it's intensity has been increasing over time but its emission spectrum has not changed. If there are any astronomers or alike out there who know more about this, please comment on this thread! This is such an interesting question, thanks for the comment! :)
@@GEOGIRL Sorry for my layman's terms but you understood emission spectrum and what I meant? lol
@@GEOGIRL We all know life is dependent on the Sun on this Planet but since there has been a reconstructed solar radiation history created...I do believe the origin of life on this planets Giant purple elephant in the Room would be the Solar emissions spectrum and type of radiation and how that solar radiation was interacting with the first organic molecules on this planet.
At 1:00, you say that you'll link to one of your carbon isotope videos in the upper-right, but it appears that you did not do so.
Oh my gosh! I can't believe I didn't catch that, thank you so much for pointing that out, I just fixed it, it should show up now :)
@@GEOGIRL For sure, I'm happy to help! Thanks for adding that link, and thanks for the great video!
Well yet another explanation why complex life evolved so late on Earth! Makes us wander if perhaps on other planets it could have met better conditions early on and evolved way earlier. So fascinating to imagine a Phanerozoic eon that is 2 billion years old or more instead of one just 540 million years old like it was the case on Earth!
Just came across this for the first time and this was fascinating. I'm an exoplanet atmosphere modeler but my office mate thinks about the Archean and I love trying to picture how incredibly bizarre Archean Earth must've looked. I've also heard it suggested that the skies would have been orange due to methane hazes, the land, such as there was, would've mostly been black due to the lack of oxidization or land based life, and the oceans might have been green due to all the dissolved unoxidized iron
Is it right to imagine that the purple phototrophs would've mostly been in stromatolite colonies in shallow seas?
So now basically I'm picturing a ocean world filled with green seas, dotted with black volcanic islands surrounded by purple lagoons, lit by orange smoggy skies?
Quick question is the purple earth hypothesis for 3.5-2.4 Bya the current scientific consensus is just a speculative idea
I would say it is scientific consensus that it is one possible hypotheses regarding the early photosynthesizers, but it is certainly not the only one and it is also incredibly difficulty to say anything too certain about organisms that long ago, especially ones that were tiny and soft bodied, and thus do not have the best fossil record. So, yes, it is a real hypothesis backed by real evidence, but take it with a grain of salt considering there are other possibilities. :)
@@GEOGIRL among all the possibilities of early photosynthesis which one is currently the most popular and favored in the scientific community
On the topic of human phototrophy, does vitamin D synthesis count? Maybe this is covered later, I haven’t finished watching
Absolutely it does! ;D
Hi Rachel! I've become a fan of your vids. You give lots of info. For example, I have always tried to find how dense were the Carboniferous forests. And you explain this in your video about this period.
Please, make a vid about
THE AZOLLA EVENT.
Was it true or is it pure speculation?
Can a single plant produce an extinction event in an era where there were lots of hervibores that could specialize to control it's expansion?
We love your knowledge. And it seams you have made a few trolls who publicly correct you for there own ideological needs. I say call them up and have a global lollipop. My 13 yo daughter is now buying her first electron microscope….an I say thank you.
OMG An electron microscope at 13! That's so amazing, she is going to have so much fun and learn so much, congrats :D
Rachel, This video is the 💣! Tons of cell bio. Lipid bilayer. Membrane bound proteins. Retinal/rhodopsin vs. chlorophyll/PS1&2 💥. Red + blue = purple ✅.
Thanks so much! I am so glad you enjoyed it ;D It is one of my all time favs for sure! I just love talking about microbes, especially ancient microbes ;)
Rachel: What if Earth wasn't the only planet that experienced this purple phase? What if this hypothesis might give us insight into potential life on exoplanets…and if the purple earth hypothesis is correct and there was a dominance of purple organisms in the early Earth, then might we be able to find another planet that's at an earlier stage of evolution of the planet, where the purple pigments might have dominated?
Earth is not a planet. There are no planets, just round lights in the sky. We are down here... the sky is up there... the only thing purple is your brain. Get a new one.
That was fascinating. Thank you
Love your videos!
Thank you! So glad you enjoy my videos ;D
Very good presentation. It is fascinating to hear about the molecules that has enabled our cells to manipulate energy (the source of life). In eukaryote cells mitochondria are the next evolutionary step on this path and pathology i mitochondria have been identified as the basis of many causes disease. Your hypothesis on the boring billion is interesting. I think the Black Sea has this kind of chemistry. The Black Sea being a fresh water lake before 7000 BC, became connected til the Mediterranean by earth quakes and salt water flowed into the lake. But fresh water kept coming from the great rivers keeping the Black Sea as a fresh water lake on the surface (200 m) and saltwater below the halocline. The chemistry of FeS makes the Black Sea black. It is also interesting that in the straits of Bosporus fresh water flows out at the surface, but saltwater flows in a a depth of 30-50 m, keeping the Black Sea salty.
You rock!❤❤❤
This was really interesting. It seems like it could be an exciting field to work with if there are any examples of the older species left or able to be reproduced.
Amazing video, i was wondering why photosintethic organism was Green.
Thanks! I am so glad you enjoyed it :)
Couldn't it also be that green light photosynthesis developed in the green light in order for organisms not competing with *their own* retinal based phototrophy?
I am sorry, could you re-word the question? I am not sure I understand, I thought I tried to convey this point in the video so I want to make sure I understand what you are asking, thanks! :)
In my opinion there are two problems with the hypothesis:
1. Chemical analysis of the oldest rocks shows that the atmosphere of the early Earth was very inert and there wouldn't have been an abundant source of organic carbon on the 3.7 Ga which makes it more likely that the first phototrophs were producing vs consuming organic carbon.
2. Although the retinol based pigments absorb more light on the surface you have to remember that the first organisms lived in water and one of the chlorophyll absorbance peaks is in the blue light range (the wavelengths that can penetrate the furthest in water). This is going to be even more important on the early Earth when the top mixing layer of the oceans would have been inundated with intense UV light.
IIRC from my college biochem courses, oxygenic photosynthesis requires some free oxygen to get started. That's at least part of the reason anoxygenic photosynthesis started first.
Did oxygen photosynthesis need free oxygen to get started? Oxygenic photosynthesis is the photosynthetic production of free oxygen. Thus, oxygen is the product of this pathway, not the reactant. So, I am not sure it needed free oxygen to get started, but I could be wrong, there could certainly be very specific biochemical details I am unaware of :)
@@GEOGIRL I'm sorry, it's been a couple decades but like I said. If I recall correctly it takes a little bit of free oxygen to get it started. My information may be out of date because college was twenty years ago. But I'm pretty sure that at least one of the enzymes in the Calvin cycle needs free oxygen to form properly. Again this is from a lecture from twenty years ago so I may be out of date.
A purple earth would be beautiful to see
That was back when Barney roamed the earth.
Adenosine Tri Phosphate.
Thank You Mr. Morris for realizing that I could be paying attention despite having ZERO finished Labs and negligible notes.
The sun has a peak in the number of photons that it emits at about 500 nm (599.6 Thz). The chlorophyll B absorbs light at about 475 nm (631 Thz). This "blue" light is more energetic than the "green" light.
I am wondering if this difference might make sense based on quantum mechanics. The light is used to "kick" electrons up into a higher energy level. This can only happen if the energy of the light and the energy needed to kick the electrons up are identical. The difference in energy of the photons at the 500 nm and 475 nm is roughly 5%.
The peak of sun light happening in the "green" part of the spectrum would suggest that plants would have evolved to be purple. The counter to this is that maybe the slightly higher energy "blue" photons can penetrate water better and have an energy that is closer to the specific energy needed to excite the electrons of the chlorophyll. This sounds like the makings of a good science experiment.
Is it possible to compete for particular spectra of light? Like, plants clearly compete for light, but it's a bit of an all-or-nothing game, isn't it? The green spectrum light wasn't passing directly through the retinol-based lifeforms, was it? Or is the implication here that they reflected enough light to enable the chlorophylls?
we would have leafy purples in our salads and purplery in our gardens
Where did the organic carbon reservoir come from, that was eaten by the heterotrophic retinal-based phototrops? Was there another type of autotrophic organic producing organism not yet based on chlorophyll around?
Fascinating. Always wondered why plants reflect reflect away the green part of the spectrum. So you say they choose a different part of the spectrum from the purple bacteria to be able to compete - by finding a different ecological niche, so to speak. But that is not so clear. It's not like purple bacteria use up all the purple in the world. Only makes sense if both kinds of bacteria are all bunched up together, literally living on top of each other and filtering the light that reaches those below. That is the implication of your theory. I would think each would stick to their own neighbourhood, where they are born, raised up, and die. In that case there is enough spectrum for all - at least until the plants killed off the purple bacteria by poisoning the atmosphere with oxygen.
Actually, it is for the exact reason you mention that this hypothesis is possible, it is that they did (and still do) live 'bunched up' or layered as you mention, in microbial mats! :) The green oxygenic phototrophs on top and the purple anoxygenic ones using the filtered light below. At least this is the case for oxygenic and anoxygenic photosynthesizers; I am not sure if it is also the case for the bacteriorhodspin-using phototrophs, but it is likely as the fossil record suggests that microbial mats were the major living 'behavior' of phototrophic microbes on this early earth :)
But I wouldn't use the word 'choose' when explaining why green phototrophs evolved, but rather that this became the most beneficial and evolutionary advantageous trait (or pigment in this case) to have as a newly evolving phototroph in a world where you share space with the more primitive guys ;) Hope that makes more sense!
@@GEOGIRL Thanks for the clarification. An interesting analogy here are layered photocells for producing electricity from light. Each layer extracts energy from a different part of the spectrum, and allows the unused portion of the spectrum pass through to the layer beneath. In this manner they can max out the amount of energy that can be extracted from each square unit of surface.
nice google slides presentation. no seriously, I feel like this is a video I'd see at school and get nostalgic over years later
Interesting about the eye absorbing light in retinal photosynthesis. The particular blue hue of the sky has a psychological effect on us giving us a feeling of well being. The lack of it for an extended time like winter periods gives some people today seasonal affective disorder (SAD) as an evolutionary adaptation. In the depths of winter in the ice age feeling like "seizing the day" and "making it all happen" by going outside in the freezing blizzard winds with no food, big game migrated away for the winter would likely mean a dead ice age man. Feeling like doing nothing is exactly the best strategy at such a time.
Fascinating...