Name: ベトベトした生き物が私たちを長生きさせるかもしれない理由 (Why Gooey Creatures Might Outlast Us All)
Uploaded: 2021-01-14T10:53:33.000Z
Duration: 5 min 43 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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[ intro ] In a way, humans are part of the one percent.

The one percent of species that hasn't gone extinct... yet, that is.

There have been five major extinction events on our planet

which, combined, have wiped out at least 99 percent

Lucky for us, humans weren't around during any of them.

But, obviously, some animals did make it through.

like jellyfish and comb jellies, have weathered all five.

And that may be thanks to the weird thing they have in common:

The main difference between gelatinous animals and the rest of us is water content.

But animals that are considered “gelatinous”

And there's no doubt that being that gooey has its perks.

After all, gelatinous bodies have independently evolved

in almost every major phylum of animals—

And gooeyness might explain why species like jellies survived mass extinctions

For example, during the late Devonian around 360 million years ago,

roughly three-quarters of Earth's species disappeared.

were a big part of that, especially in oceans.

Which makes sense, because oxygen is kind of important —

we've been pretty dependent on the stuff.

But gelatinous animals can tolerate lower oxygen levels

In part, that's because they literally don't breathe.

They just soak up oxygen from their surroundings.

Because they're overwhelmingly made of water, O2

can diffuse directly from the water around them into the water inside them.

So there's no need for dedicated respiratory structures like gills, lungs, or noses.

They don't even need blood to shuttle oxygen around.

And that means they need less oxygen overall,

because those complex tissues require a bunch of it to function well.

Jellies are also able to store oxygen inside their structural goo,

So basically, they have a reserve tank that can help them make it through temporary oxygen

Of course, hypoxic events aren't the only thing animals have to survive during an extinction.

Sudden rises in seawater acidity have also been to blame for a lot of mass death.

These tend to be tied to pulses of volcanic activity,

And dissolved CO2 reacts with seawater to make it more acidic.

Acidification can also happen without volcanoes.

Like, that big asteroid that wiped out non-avian dinosaurs about 66 million years ago?

Researchers think it vaporized a bunch of sulfur-rich rocks.

That led to acidic rains, which caused the ocean's pH to plummet.

acidification is a huge problem for lots of marine animals.

See, the chemical reactions that drive acidification

also reduce the number of carbonate ions in seawater —

ions that many species need to build their shells or skeletons.

So in acidic waters, carbonate shells and skeletons dissolve or cost more to construct.

And that makes creatures like corals and clams extremely sensitive

Even animals that don't build carbonate body parts

because the extra acid messes with their blood chemistry.

But acidification isn't such a big deal if you don't have blood or carbonate parts.

Some jellies, for instance, can grow and reproduce in extremely acidic conditions.

Finally, just in case acidification and hypoxia weren't hard enough to survive,

extinction events also tend to mean less food is available.

That's kind of the definition of a mass extinction.

And that means anything still living has less to eat.

It turns out even that is not as big a problem if you're gooey.

One of the main reasons animals eat is to obtain carbon:

Gelatinous bodies contain very little carbon to begin with,

Plus, when you're gooey, you can really maximize your food intake,

because every little morsel in the water sticks to your mucusy feeding parts!

Also, thanks to being mostly water, gelatinous creatures are close to neutrally buoyant

And that means they don't need to exert much energy to swim.

So basically, it seems like, if you're made of goo,

Which might explain why gelatinous organisms

have outlasted everything from trilobites to T. rex.

And they might make it through the next extinction crisis, too —

the one happening right now because of us.

We're already seeing signs of extreme biodiversity loss,

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