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Lack of food, no sunlight and nuclear disaster might mean the end of the world for humans, but these 9 animals just might make it.

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Sources:
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http://www.sciencemag.org/news/2012/11/bdelloids-surviving-borrowed-dna
http://entnemdept.ifas.ufl.edu/walker/ufbir/chapters/chapter_21.shtml
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http://www.nytimes.com/2015/09/08/science/the-tardigrade-water-bear.html
http://www.asknature.org/strategy/c1eb0f25d3e091f568ce26c0c6f8646fl
http://mutage.oxfordjournals.org/content/24/3/259.full
https://www.researchgate.net/publication/225549141_A_silent_invasion
http://www.nefsc.noaa.gov/publications/tm/tm148/tm148.pdf
http://www.ncbi.nlm.nih.gov/pubmed/26079722

Images:
https://commons.wikimedia.org/wiki/File%3ADromedary_camel_dahab_egypt.jpg
https://commons.wikimedia.org/wiki/File%3ADromedary_camel.jpg
https://commons.wikimedia.org/wiki/File%3AChapultepec_Zoo_-_Dromedary_camel.jpg
https://commons.wikimedia.org/wiki/File%3ADromedary_Camel_15.jpg
https://commons.wikimedia.org/wiki/File%3AMerriam's_Kangaroo_Rat.jpg
https://commons.wikimedia.org/wiki/File%3ACataglyphis_bicolor_casent0104612_profile_1.jpg
https://commons.wikimedia.org/wiki/File%3ARiftia_tube_worms_Galapagos_2011.jpg
https://commons.wikimedia.org/wiki/File%3ADmawsoni_Head_shot.jpg
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https://commons.wikimedia.org/wiki/File%3ACyprina1000111.JPG
https://commons.wikimedia.org/wiki/File%3ARoachies.JPG
https://commons.wikimedia.org/wiki/File%3ABdelloid.JPG
https://commons.wikimedia.org/wiki/File%3AGlace05.jpg

 Introduction (0:00)


A lot of animals can survive under very specific conditions. If you mess with their habitat, they start to die out. Others are more versatile, and can adapt when their environment changes. But a few animals are really, really good at dealing with extremes -like, way better than humans are. We're talking extreme heat and very little water, lack of food, no sunlight, nuclear disaster.

All of these scenarios might mean the end of the world for the humans, and some of them could wreck the planet enough to wipe out all life, eventually. but these 9 animals do have a decent chance of survival.

Say there's a Mad Max-style apocalypse, and we end up with a desert planet that's hot and almost completely dry. Anything that survived would need to be able to withstand high temperatures and live on very little water. 

 Dromedary Camel (0:49)


The dromedary camel fits that bill, and its secret is in the hump on its back. This humps is not full of water, though. It's actually fat. And there are a few reasons why a big ol' lump of fat is helpful in the desert. 

Most mammals have fat distributed around their bodies, but camels keep it all up on their backs. Fat is insulating. This is why seals and whales have big coats of blubber, it keep them warm.  But obviously camels don't need to keep warm when it's already blazing hot out, so they pile it all in one place. Also, fat is a nice energy reserve when you're travelling across the desert with little food.

Then there's the fact that breaking down fat into energy has a helpful byproduct, water. The thing is, to take in enough oxygen to break down all that fat, the camel has to breathe a lot. But when you breathe you exhale water vapor, so it should actually be a net loss of water for the camel. The camel gets around this problem by re-absorbing water from the air as it breathes out. 

A camel's nasal cavity has a ton of surface area, all covered with tissue that water can stick to. As air passes by, the water gets drawn out and stays inside the camel. Camels can go for weeks or even months without a drink of water this way. 

There's another mammal that might not need to drink water, ever.

 Merriam's Kangaroo Rat (1:51)


Merriam's kangaroo rat is a North American rat. It isn't actually related to kangaroos, it's just named that way because it gets around by hopping. Its body also happens to be incredibly good at retaining water, Merriam's kangaroo rats seem to get all the hydration they need from the seeds they eat. 

It's enough water for them because they use it incredibly efficiently. They don't sweat or pant to cool off, and even their waste has almost no water in it. Once water's in their body or generated by their metabolism, they hang onto it. If you offered a Merriam's kangaroo rat a glass of water, it'd probably be like, no thanks, I just had seeds this morning. 

Merriam's kangaroo rats are currently threatened in some places because of humans taking over their habitat, but if water suddenly becomes harder to find, we'll be the ones in trouble. 

 Desert Scavenger Rat (2:29)


Then there's the Sahara desert scavenger ant. An insect so hardcore that when the temperature get too hot for other insects to handle, it feasts on their corpses. These guys would be the ultimate winners on an overheated planet.

There are several heat-tolerant species of desert ants, but the Sahara one is the all-time champion. It actively goes out and looks for food at temperatures higher than fifty degrees Celsius.In those conditions the surface of the sand itself is closer to seventy, the temperature of an oven on the lowest setting.

And, I really can't let this go, their food source is other insects who died because it was just too hot. They raid the bodies of their fallen comrades. How very incredibly post-apocalyptic of them. 

They outlast other insects in three ways. First, they're super speedy, so they can zip across burning sands. They also have long legs that lift them high above the surface, proportionally long for an ant that is, since the further you get from the sand, the cooler the air. And for that same reason they'll often climb plant stalks to get as far from the sand as possible cool off. 

Now let's talk about the opposite extreme. What if the sun totally disappeared, in some comic book villain's plot to destroy all life on Earth? Well, the plan wouldn't work, because not all life on Earth  gets its energy from the sun. 

 Giant Tube Worms (3:32)


Giant tube worms live at the bottom of the ocean where light can't reach, around ocean vents that spew boiling water and chemicals that, to us, would be deadly. Their secret to success is their symbiotic relationship with some strange bacteria. 

The hydrogen sulfide that comes out of the deep sea vents is toxic to most forms of life, but the bacteria use it to get energy. These bacteria also produce organic molecules that the tube worms need to live. In return, the bacteria get to live inside the tube worm's body cavity, which is relatively safe and sheltered. 

So, if the sun were to vanish, as long as the deep sea vents functioned, these worms would be just fine. Until the oceans froze, that is. 

speaking of freezing, what if the planet got very cold?

 Antarctic Toothfish (4:09)


Well, I'm happy to report the Antarctic toothfish would probably be just fine. This fish lives in waters so cold, its tissues should freeze solid. But they don't, because it has a gene for antifreeze. 

It's not like the antifreeze that you put in your car. It's a glycoprotein, a molecule made of both amino acids and sugar. This glycoprotein circulates in the blood binding to any ice crystals floating around in the bloodstream and stopping them from getting any bigger. Then, the fish can eliminate both the protein and ice from its body. 

This biological antifreeze has actually evolved more than once, in both Arctic and Antarctic fish. Which makes total sense, considering how cold it gets in both of those places.

So these fish species would be able to go on feeding and swimming happily in frigid oceans where most animals would die. 

Survival isn't all about temperature. Sometimes there's just very little food available. And in that case, some animals can afford wait until things get better. 

 Ocean Quahog (4:55)


Take the ocean quahog, a bivalve mollusc that doesn't seem to age. One specimen was confirmed to be 507 years old when it was discovered. It was nicknamed Ming, after the Chinese dynasty in power when it was born.

How is it possible for an animal to live so long? Scientist think the ocean quahog has two main adaptations: First, it has a very slow metabolism, using only a tiny bit of oxygen at a time. And oxygen use might have a lot to do with aging, since the byproducts of oxygen metabolism, called free radicals, are damaging to cells.

So the ocean quahog is very, very good at limiting free radical damage to its cells. But some biologists don't subscribe to this free-radical idea, and there may also be some genetic secret to the quahog's longevity that we haven't discovered yet. Either way, if food is scarce, the quahog doesn't care much, it'll just slow down its growth for a while, biding its time. Even with very few resources and just a trickle of oxygen, these things can go on for hundreds of years. 

 Immortal Jellyfish (5:45)


There's another animal that has an even weirder trick. The immortal jellyfish, which we've talked about before, can literally age backwards.

Normally, jellyfish reproduce by developing from a tiny larva into a polyp. Then, the polyp settles down on the ocean floor and buds to give off medusae, the familiar bell-shaped creatures we think of as jellyfish. And if an immortal jellyfish medusae is injured or faced with starvation, it can turn itself back into a polyp. 

During this process, called reverse development, the jellyfish's cells revert to a sort of blob that doesn't do much. And while that blob is developing into a polyp, it doesn't need a lot of food. The polyp then turns into medusae genetically identical to the original, meaning that if the oceans don't have much food, the immortal jellyfish can start over and try again until things look better.

 Cockroaches (6:26)


Another way the world might end? Nuclear catastrophe. The radiation that comes from nuclear blasts shreds DNA like paper, so most forms of life have a rough time dealing with it. But people often talk about cockroaches sticking around even if we humans wipe ourselves out with nuclear weapons.

And there is some truth to that. Cockroaches can withstand radiation doses that would kill a human. They've been spotted alive and well in the wake of nuclear explosions, and they seem to be able to handle at least ten times more radiation than humans can. 

That said, it's not just cockroaches. All insects are more resistant to radiation than humans. We're not exactly sure why this is, but there are a couple of running theories out there.

For one thing, just like the ocean quahogs, insect cells seem to be very good at resisting damage by free radicals. They're also better at repairing their DNA once isn't been damaged. Even in cases where humans cells would die, insects cells just fix themselves and keep going. So insects in general are probably better prepared to cope with nuclear disaster than humans are. Cockroaches included.

 Bdelloid Rotifers (7:15)


There are tiny freshwater invertebrates that even put roaches to shame in the radiation resistance game. They're called bdelloid rotifers, and their lives are just incredibly weird.

See, unlike most animal species, bdelloids reproduce asexually. Most animals use sexual reproduction as a way to introduce variety in their gene pools, which makes it harder for threats to wipe out the whole population. But the bdelloids have been going strong without sex for 80 million years. Instead, they change up their gene pool by stealing DNA from other species. 

Scientists haven't quiet figured out how rotifers come by DNA from other species, but we do know that they're pilfered genes from plants, bacteria and fungi. This gives the rotifers a varied gene pool even without sexual reproduction, but also makes them resistant to radiation. To steal DNA, they have to be pretty good at joining together separate pieces of DNA. Which means if radiation messes with their DNA, they're really good at fixing it. 

 Conclusion (8:03)


So there are plenty of animals with survival skills that might make us humans seem relatively fragile. And no matter what kind of planet we leave behind, odds are that some animals will last longer than we will. 

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