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  • This is Goliath, the krill.

  • Don't get too attached.

  • Today this 1 centimeter crustacean

  • will share the same fate as 40 million of his closest friends:

  • a life sentence in the belly of the largest blue whale in the world.

  • Let's call her Leviatha.

  • Leviatha weighs something like 150 metric tons,

  • and she's the largest animal in the world.

  • But she's not even close to being the largest organism by weight,

  • which is estimated to equal about 40 Leviatha's.

  • So where is this behemoth?

  • Here, in Utah.

  • Sorry, that's too close.

  • Here.

  • This is Pando, whose name means “I spread out.”

  • Pando, a quaking aspen, has roughly 47,000 genetically identical clone trunks.

  • Those all grow from one enormous root system,

  • which is why scientists consider Pando a single organism.

  • Pando is the clear winner of world's largest organism by weight

  • an incredible 6 million kilograms.

  • So how did Pando get to be so huge?

  • Pando is not an unusual aspen from a genetic standpoint.

  • Rather, Pando's size boils down to three main factors:

  • its age, its location, and aspens' remarkable evolutionary adaptation

  • of self-cloning.

  • So first, Pando is incredibly expansive because it's incredibly old.

  • How old exactly?

  • No one knows.

  • Dendrochronologist estimates range from 80,000 to 1 million years.

  • The problem is, there's no simple way to gauge Pando's age.

  • Counting the rings of a single trunk will only account for up to 200 years or so,

  • as Pando is in a constant cycle of growth, death, and renewal.

  • On average, each individual tree lives 130 years,

  • before falling and being replaced by new ones.

  • Second: location.

  • During the last ice age, which ended about 12,000 years ago,

  • glaciers covered much of the North American climate

  • friendly to aspens.

  • So if there were other comparably sized clonal colonies,

  • they may have perished then.

  • Meanwhile, Pando's corner of Utah remained glacier-free.

  • The soil there is rich in nutrients that Pando continuously replenishes;

  • as it drops leaves and trunks,

  • the nutrients return to nourish new generations of clones.

  • Which brings us to the third cause of Pando's size: cloning.

  • Aspens are capable of both sexual reproduction

  • which produces a new organism

  • and asexual reproductionwhich creates a clone.

  • They tend to reproduce sexually when conditions are unfavorable

  • and the best strategy for survival is to move elsewhere.

  • Trees aren't particularly mobile, but their seeds are.

  • Like the rest of us, sexual reproduction is how Pando came into the world

  • in the first place all those tens or hundreds of thousands of years ago.

  • The wind or a pollinator carried pollen from the flower of one of its parents

  • to the other, where a sperm cell fertilized an egg.

  • That flower produced fruit, which split open,

  • releasing hundreds of tiny, light seeds.

  • The wind carried one to a wet spot of land in what is now Utah,

  • where it took root and germinated into Pando's first stem.

  • A couple of years later, Pando grew mature enough to reproduce asexually.

  • Asexual reproduction, or cloning,

  • tends to happen when the environment is favorable to growth.

  • Aspens have long roots that burrow through the soil.

  • These can sprout shoots that grow up into new trunks.

  • And while Pando grew and spread out, so did our ancestors.

  • As Hunter-gatherers who made cave paintings, survived an ice age,

  • found their way to North America, built civilizations in Egypt and Mesopotamia,

  • fought wars, domesticated animals, fought wars, formed nations,

  • built machines,

  • and invented the internet, and always newer ways to fight wars.

  • Pando has survived many millennia of changing climates and encroaching ice.

  • But it may not survive us.

  • New stems are growing to maturity much more slowly than they need to

  • in order to replace the trunks that fall.

  • Scientists have identified two main reasons for this.

  • The first is that we've deprived Pando of fire.

  • When a fire clears a patch of forest, Aspen roots survive,

  • and send shoots bursting up out of the ground by the tens of thousands.

  • And secondly, grazers like herds of cattle and mule deer

  • whose natural predators we've hunted to the point of local elimination

  • are eating Pando's fresh growth.

  • If we lose the world's largest organism, we'll lose a scientific treasure trove.

  • Because Pando's trunks are genetically identical,

  • they can serve as a controlled setting for studies

  • on everything from the tree microbiome

  • to the influence of climate on tree growth rates.

  • The good news is, we have a chance to save Pando,

  • by reducing livestock grazing in the area

  • and further protecting the vulnerable young saplings.

  • And the time to act is today.

  • Because as with so many other marvels of our natural world,

  • once they're gone it will be a very, very long time before they return.

This is Goliath, the krill.

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B2 organism reproduction largest cloning aspen growth

The world’s largest organism - Alex Rosenthal

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    林宜悉 posted on 2020/12/07
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