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  • Hi! I'm Emily from MinuteEarth. Or, as I've sometimes heard it pronounced, "my-nute Earth."

  • Coming up, we've got four short stories about the science of size,

  • why big things are big, small things are small,

  • and as far as Mother Nature is concerned, size really does matter.

  • First up, a quest for the biggest organism on the planet.

  • Blue whales are the biggest animals ever to exist on Earth.

  • They can weigh upwards of 150 tons, which is more

  • than the largest dinosaurs. But the blue whale is not the biggest living thing.

  • That title goes to... well, it depends on what you mean by "biggest." The tallest may be

  • a California redwood nicknamed "Hyperion." At a towering 115 meters,

  • this giant is taller than the Statue of Liberty. The most extensive organism is

  • a very old humongous fungus that covers a whopping

  • 2385 acres in a national forest in Oregon. At the base of trees, bunches of

  • honey mushrooms appear. They are the fruiting bodies produced by the fungus,

  • which otherwise lives out of sight. Imagine if apple trees grew underground

  • and only the apples apples were visible to us. That's basically what the fungus does,

  • except that it spreads its mycelia not just through the soil, but also through the

  • roots and bark of trees in the forest, attacking them and stealing their

  • nutrients, so it can continue spreading outwards. However, if we're talking about the

  • good old heaviest organism ever found, that prize goes to a giant panda

  • living high on a Utah plateau.

  • Just kidding. It goes to a single quaking aspen named "Pando"

  • that weighs over 6000 tonnes, as much as 40 blue whales. If you go to the

  • Fish Lake National Forest, though, you won't see a giant tree trunk. You'll just

  • see a forest of regular sized trees. But thanks to genetic testing,

  • we've learned that this stand of aspen covering 106 acres of land is actually a

  • single clonal organism that grew from a lone seed long ago. That single tree was

  • able to spread so much because its roots send up shoots that grow into what look

  • like individual trees. Since all 47,000 trees are part of the same organism, the

  • forest behaves somewhat unusually. For example, the entire forest transitions

  • simultaneously from winter to spring and uses its vast

  • network of roots to distribute water and nutrients from trees with plenty to

  • trees in need. Speaking of water, if you include water when weighing these giant

  • organisms, then the humongous fungus might actually way more than Pando but

  • foresters at least care only about the mass actually produced during growth, the dry mass.

  • And since fungi are mostly water,

  • Pando wins. Either way it's likely that some of the below ground connections

  • whether roots or mycelia, have become severed over time, meaning these giants

  • are probably comprised of smaller but still ginormous and genetically

  • identical patches. And finally, because of the extensive testing required to

  • confirm "biggest anything" claims, the fungus and Aspen can only profess to be

  • the largest living organisms ever found. There may be even bigger monsters

  • lurking right under our feet just waiting to be discovered.

  • So, it's possible that the biggest organism hasn't been discovered yet,

  • even if it isn't possible that that organism is an underground panda.

  • The thing is, though, animals don't just wake up one day gigantic. Something weird

  • has to happen to make them that way.

  • Animals come in all different sizes but

  • usually over evolutionary time each type of animal stays roughly the same size.

  • Every once in a while though, something crazy happens that allows an animal to

  • get truly gigantic. Take insects and other arthropods, which have tiny bodies,

  • in part because they breathe by sponging up air through their exoskeletons,

  • and the available oxygen can only diffuse so far before getting used up. If they had

  • bigger bodies oxygen wouldn't reach far enough inside. But about 300 million years ago,

  • Earth's atmospheric oxygen levels spiked. With more oxygen in the

  • air, arthropods' bodies could grow way bigger,

  • leading to mega-bugs like a dragonfly the size of an eagle, and a millipede the

  • size of a two-person kayak. Dinosaurs on the other hand got pretty darn big

  • without any outside help, but at some point they hit a limit due to the

  • so-called "square-cube law": body strength is based on a cross sectional area of bones and muscles,

  • but weight is based on volume, and just like doubling the height

  • of a cube causes its cross-sectional area to

  • get four times larger but its volume to get eight times larger, when an animal

  • gets bigger, it does get stronger, but it gets WAY heavier. Fossil evidence

  • suggests that dinos were nearing the size of which they could no longer lug

  • around their own bodies, when they stumbled upon an evolutionary

  • breakthrough: a system of air pockets and air sacs throughout their skeletons that

  • allow them to get bigger without getting heavier, and have incredibly long but light

  • necks, which granted them access to a huge bounty of leaves. Eventually though,

  • a group of land animals got around the square-cube problem altogether by

  • climbing back into the water, which buoyed their weight. And since they took

  • their lungs with them into the water, they could breathe oxygen-rich air,

  • rather than being stuck with oxygen-poor water, allowing these mammals to grow

  • almost twice as big as the biggest fish. But these giant creatures just didn't

  • have enough food to get any gianter than that. Then, a few million years ago,

  • changing ocean currents brought tons of nutrients up from the depths, which fuel

  • huge localized phytoplankton blooms, which in turn attracted enormous

  • concentrations of scrumptious zooplankton. With this new "krillion"-calorie diet

  • together with their air-breathing lungs and water-supported bodies,

  • blue whales quickly tripled in size to become not just gigantic, but truly

  • the largest animals to have ever lived. And that is certainly something to spout about.

  • In the ocean life comes in all sizes.

  • It turns out that we humans need to be eating more of the small stuff.

  • Anyone who goes fishing probably has a story about the one that got away.

  • "It was this big, don't cha know!" Yeah, that was a bummer, but it's actually quite important

  • that big fish get away, both for fish and fishermen. For most of the species that

  • we fish, commercial and recreational fishermen are only allowed to keep

  • individuals above a minimum legal size. The idea behind these laws is to protect

  • juveniles so they can grow big enough to reproduce at least once before becoming

  • our dinner. In theory, that means there will always be enough fish for dinner

  • tomorrow, and ensuring dinner for tomorrow is important enough that the

  • English Parliament discussed protecting youngthat is, smallfish as early as 1376,

  • and today it's a common regulation for fisheries worldwide,

  • except it doesn't really work. First, large individuals have the

  • greatest number of successful offspring, both because bigger fish produce more

  • eggs and because the eggs they produce also contain a more generous food supply

  • for the baby fishies. So by removing the largest individuals of a given species,

  • we severely decrease the population's ability to replenish itself. Second, if we

  • only remove the largest fish, that means fish that are small for their age and

  • thus smaller when they first reproduce, are more likely to live long enough to

  • make babies, so individuals with small fish genes tend to stay in the water,

  • reproduce and pass on their genes to new generations, while big fish and big fish genes

  • become rarer and rarer. We're basically breeding smaller fish,

  • unintentionally, and it's not a small change. Size-selective fishing has caused

  • the body mass of large commercial fish to be cut in half over the last 40 years.

  • Let me say that again. Heavily-fished fish are now half the weight they used

  • to be. Six-year-old haddock, for example, weigh 40% of what they did in 1970

  • Imagine if full-grown men weighed 65 pounds! Clearly, size-selective fishing

  • means fewer and smaller fish in the water, which suggests it's not the best

  • way to keep our fish supply stocked for future human generations.

  • And in fact, there's a new idea called "balanced harvesting" ready to save the

  • day. Instead of reeling in all the largest individuals, fishermen would

  • catch a smaller number of fish across a wider range of sizes, keeping the numbers

  • and sizes of fish... well, balanced. However, old habits die hard, and the use of size

  • limits is deeply ingrained in our collective fisheries management DNA, but

  • sooner rather than later, we'll have to accept that it's good to

  • let some of the big ones get away, for only they can change the course of fish-tory.

  • Fish-tory! We can't be proud of all of our puns, but while we're talking tiny and

  • water, let's talk about tiny water. How many water molecules does it take to make a drop?

  • Somewhere inside of every raindrop is a tiny impurity―a touch of

  • salt, a speck of soot, a grain of claythat's absolutely crucial to the

  • raindrop's existence. In fact, without these microscopic pieces of dirt there

  • would be no rain because water vapor can't condense into droplets on its own,

  • which is kind of weird because water molecules like each other. If they didn't,

  • they wouldn't cling to each other like this, and in the air vaporized water

  • molecules collide and stick together all the time, but they also break apart all

  • the time, thanks to bond-breaking heat energy.

  • Only when the air cools down past a certain point called the "dew point" does this

  • breaking apart slow down enough for little clusters of water molecules to

  • grow into droplets. But actually, that's only true if the cluster is big to start with.

  • If it's too small its surface is so curved that the molecules on the outside

  • have few neighbors to bond to which makes them easy to break off so the

  • cluster as a whole has higher chances of losing molecules than gaining them, even

  • below dew point, which means that up until a certain critical size, a cluster's

  • chances of shrinking are better than its odds of growing. Unfortunately, that

  • critical size is 150 million molecules, and while there are

  • millions of 5-molecule clusters in a golf ball-sized volume of air at dew point, odds are that

  • only one of those clusters will grow to a size of 10, and you'd need a golf ball

  • of air 10 million miles across to find a single 50 molecule cluster, which

  • basically means that clusters of water molecules

  • never get to that 150 million mark on their own. Fortunately, they don't have to!

  • They can start off at that critical size by condensing onto one of the gajillions

  • of little pieces of dirt floating in our atmosphere and then grow and grow until

  • they're a droplet in a rain cloud and ultimately it's these little pieces of

  • dirt surrounded by water that make life possible on our big piece of dirt

  • surrounded by water.

  • And, from my spot on this big piece of dirt, thanks for watching!

Hi! I'm Emily from MinuteEarth. Or, as I've sometimes heard it pronounced, "my-nute Earth."

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MinuteEarth Explains: Size

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    joey joey posted on 2021/04/30
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