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  • Without water, a human can only survive for about 100 hours.

  • But there's a creature so resilient that it can go without it for decades.

  • This one millimeter animal can survive both the hottest

  • and coldest environments on Earth,

  • and can even withstand high levels of radiation.

  • This is the tardigrade,

  • and it's one of the toughest creatures on Earth,

  • even if it does look more like a chubby, eight-legged gummy bear.

  • Most organisms need water to survive.

  • Water allows metabolism to occur,

  • which is the process that drives all the biochemical reactions

  • that take place in cells.

  • But creatures like the tardigrade, also known as the water bear,

  • get around this restriction with a process called anhydrobiosis,

  • from the Greek meaning life without water.

  • And however extraordinary, tardigrades aren't alone.

  • Bacteria,

  • single-celled organisms called archaea,

  • plants,

  • and even other animals can all survive drying up.

  • For many tardigrades,

  • this requires that they go through something called a tun state.

  • They curl up into a ball,

  • pulling their head and eight legs inside their body

  • and wait until water returns.

  • It's thought that as water becomes scarce

  • and tardigrades enter their tun state,

  • they start synthesize special molecules,

  • which fill the tardigrade's cells to replace lost water

  • by forming a matrix.

  • Components of the cells that are sensitive to dryness,

  • like DNA,

  • proteins,

  • and membranes,

  • get trapped in this matrix.

  • It's thought that this keeps these molecules locked in position

  • to stop them from unfolding,

  • breaking apart,

  • or fusing together.

  • Once the organism is rehydrated, the matrix dissolves,

  • leaving behind undamaged, functional cells.

  • Beyond dryness, tardigrades can also tolerate other extreme stresses:

  • being frozen,

  • heated up past the boiling point of water,

  • high levels of radiation,

  • and even the vacuum of outer space.

  • This has led to some erroneous speculation

  • that tardigrades are extraterrestrial beings.

  • While that's fun to think about,

  • scientific evidence places their origin firmly on Earth

  • where they've evolved over time.

  • In fact, this earthly evolution has given rise

  • to over 1100 known species of tardigrades

  • and there are probably many others yet to be discovered.

  • And because tardigrades are so hardy, they exist just about everywhere.

  • They live on every continent, including Antarctica.

  • And they're in diverse biomes including deserts,

  • ice sheets,

  • the sea,

  • fresh water,

  • rainforests,

  • and the highest mountain peaks.

  • But you can find tardigrades in the most ordinary places, too,

  • like moss or lichen found in yards,

  • parks,

  • and forests.

  • All you need to find them is a little patience and a microscope.

  • Scientists are now trying to find out whether tardigrades use the tun state,

  • their anti-drying technique,

  • to survive other stresses.

  • If we can understand how they, and other creatures,

  • stabilize their sensitive biological molecules,

  • perhaps we could apply this knowledge to help us stabilize vaccines,

  • or to develop stress-tolerant crops that can cope with Earth's changing climate.

  • And by studying how tardigrades survive

  • prolonged exposure to the vacuum of outer space,

  • scientists can generate clues about the environmental limits of life

  • and how to safeguard astronauts.

  • In the process, tardigrades could even help us answer a critical question:

  • could life survive on planets much less hospitable than our own?

Without water, a human can only survive for about 100 hours.

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B2 US TED-Ed tardigrade survive water matrix earth

【TED-Ed】Meet the tardigrade, the toughest animal on Earth - Thomas Boothby

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    a412087311 posted on 2017/07/17
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