How a single-celled organism almost wiped out life on Earth – Anusuya Willis
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How a single-celled organism almost wiped out life on Earth – Anusuya Willis


There’s an organism
that changed the world. It caused both the first mass extinction
in Earth’s history and also paved the way for complex life. How? By sending the first free oxygen
molecules into our atmosphere, and they did all this
as single-celled life forms. They’re cyanobacteria, and the story of these simple organisms that don’t even have nuclei
or any other organelles is a pivotal chapter
in the story of life on Earth. Earth’s atmosphere wasn’t always
the oxygen-rich mixture we breathe today. 3.5 billion years ago, the atmosphere
was mostly nitrogen, carbon dioxide, and methane. Almost all oxygen was locked up
in molecules like water, not floating around in the air. The oceans were populated by
anaerobic microbes. Those are simple, unicellular life forms
that thrive without oxygen and get energy by scavenging
what molecules they find. But somewhere between
2.5 and 3.5 billion years ago, one of these microbial species, probably floating
on the surface of the ocean, evolved a new ability: photosynthesis. Structures in their cell membrane
could harness the energy from sunlight to turn carbon dioxide and water
into oxygen gas and sugars, which they could use for energy. Those organisms were the ancestors
of what we now call cyanobacteria. Their bluish color comes from
the blue-green pigments that capture the sunlight they need. Photosynthesis gave those ancient bacteria
a huge advantage over other species. They could now produce their own energy from an almost endless supply
of raw ingredients, so their populations exploded and they started polluting the atmosphere
with a new waste product: oxygen. At first, the trickle of extra oxygen was
soaked up by chemical reactions with iron or decomposing cells, but after a few hundred million years, the cyanobacteria were producing oxygen
faster than it could be absorbed, and the gas started building up
in the atmosphere. That was a big problem for the rest
of Earth’s inhabitants. Oxygen-rich air
was actually toxic to them. The result? About 2.5 billion years ago was a mass
extinction of virtually all life on Earth, which barely spared the cyanobacteria. Geologists call this
the Great Oxygenation Event, or even the Oxygen Catastrophe. That wasn’t the only problem. Methane had been acting as a potent
greenhouse gas that kept the Earth warm, but now, the extra oxygen reacted with
methane to form carbon dioxide and water, which don’t trap as much heat. The thinner atmospheric blanket caused Earth’s first,
and possibly longest, ice age, the Huronian Glaciation. The planet was basically
one giant snowball for several hundred million years. Eventually, life adjusted. Aerobic organisms,
which can use oxygen for energy, started sopping up some of the excess
gas in the atmosphere. The oxygen concentration rose and fell until eventually it reached
the approximate 21% we have today. And being able to use
the chemical energy in oxygen gave organisms the boost they needed
to diversify and evolve more complex forms. Cyanobacteria had a part
to play in that story, too. Hundreds of millions of years ago, some other prehistoric microbe
swallowed a cyanobacterium whole in a process called endosymbiosis. In doing so, that microbe acquired
its own internal photosynthesis factory. This was the ancestor of plant cells. And cyanobacteria became chloroplasts, the organelles that carry out
photosynthesis today. Cyanobacteria are still around
in almost every environment on Earth: oceans, fresh water, soil, antarctic rocks, sloth fur. They still pump oxygen
into the atmosphere, and they also pull nitrogen out to
fertilize the plants they helped create. We wouldn’t recognize life on Earth
without them. But also thanks to them, we almost didn’t have
life on Earth at all.

100 thoughts on “How a single-celled organism almost wiped out life on Earth – Anusuya Willis

  1. How did the cyanobacteria who were producing oxygen suddenly grew the brains to start absorbing it? These how life began theories rarely make complete sense.

  2. So basically, what people will get from this is that they can keep harming the environment because they'll think it'll wipe out, but also diversify species lol.

  3. 1:10 They did 2.5 billion years ago what humans cant do synthetically(producing sugars with h2o and sunlight) even today.

  4. Sooo.. maybe it's just "part of the natural process", maybe even expected and necessary, not at all a bad thing, at least in the sense of evolution of life on earth in general, that we, humans, will cause the next big extinction, including our own, to (maybe? hopefully?) give way to new, better, and more evolved, species?

  5. "ay yo what if we just stopped using chemicals for energy and used whatevers up there lmao" -cyanobacteria probably

  6. 2.5 billion years ago
    Somewhere in the ocean
    Some-tiny-bacteria: "We are cyanobacteria. We are the most evolved organisms. We will now pollute the earth with oxygen! Muhahaha!"
    first mass extinction

    Now
    Everywhere in earth
    Some-ape-with-brainz: "We are humans. The most evolved organisms! And we are gonna pollute the earth with
    everything Muhahahaha!"
    sixth mass extinction

    Earth: "I hate evolution."

  7. Ignore this comment for right now. I'm not 100% confident it's true. But if you don't care about potentially incorrect facts and you're curious of what i have to say then read on i guess.
    And now i heard there's concern about a new bacteria that doing the same but instead of releasing oxygen, it releases chlorine gas. I feel like i saw a story about it. I tried ducking it but couldn't find anything about any articles. Maybe i dreamed it but it feels like a real memory.

  8. I don't know how these scientist suddenly come up with new theories about ancient earth. They're all philosophies , some of them cantt be true

  9. Am I the only one who thinks this narrator needs to choose another profession? Her clipped and awkward pronunciation, in addition to her obvious difficulty in pronouncing the letter ‘s’ is extremely distracting.
    Great vid though!

  10. AOC must watch this. Anyway, I'm not having my smoking gas guzzling excuse for a car fixed. To much oxygen is bad for you.

  11. Earth fought to reduce oxygen over-production to save all life forms back then.

    Now She's fighting to keep every oxygen she can get to save all life forms today.

    poor Earth.

  12. I read a book that unequivocally proves this video false. According to this book a holy entity made Earth just by thinking about it.

  13. More pseudoscience bullish!t! “Billions of years ago, some unknown bacteria ‘developed’ the ability of photosynthesis”, with no explanation of how this is possible! If the first life form was Cyanobacteria, a single celled organism WITHOUT a nuclei, where did the single celled organisms WITH NUCLEI come from? Pseudoscience also ignores the problem with no oxygen in the atmosphere, there is no ozone (O3) layer to block the deadly UV radiation from the Sun ☀️!

  14. environment activists: we need to plant more trees to save the earth and increase the oxygen supply.

    me: no. we need more sloth 3:43

  15. So according to the video, cyanobacteria are responsible for the evolution of David Bowie (3:08).

    We have an anaerobic bacterium to thank for Ziggy Stardust!

  16. Fancy hypothesis presented as facts. No wonder why some people choose to believe the bible over science when its done like this.

  17. x: only another massive asteroid can make the next mass extinction happen!
    human : hold my atomic bomb and on the count of 3 say goodbye to earth.

  18. What if this is like a trend of nature…

    Cyanobacteria lead to the existence of complex beings, by causing extinction of previous less complex beings…

    We humans are like cyanobacteria who are changing the earth, so more complex beings arise…

    Just a thought, and I will be glad to hear your all suggestions!!😄

  19. To all the species that were extinct that time, don't worry, humans will Avenge you… humans are emiting carbon dioxide like there's no tomorrow

  20. So you're saying that the Cyanobacteria accidentally saved life on Earth by accidentally killing almost all life on Ea- Wait a second… Lark was right… HOLD UP!

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