Life #1 - Dead, Alive and Other States

When I was a kid, I remember the Big Book of Amazing Facts startled me when it said there was no definition for the term “life”. How can a term life “life” not have a definition? Now, as an adult, I found myself reading Carl Zimmer’s book on the same theme – that life defies definition.

 

In Life’s Edge, Zimmer starts with the contradiction. Even babies follow dots on a screen that seem to move with a purpose but not dots moving randomly:

“Our knowledge of life… arises long before we can tell ourselves what we know.”

If something can live, it has two states, right? Alive or dead. Think again. Take the tiny animalcules that Antony Van Leeuwenhoek, the inventor of the microscope, found in water. If he let the water evaporate, most animalcules would burst (and die) as they dried. But not all. Some animalcules didn’t burst – it shrank into a smaller version of itself and became motionless. If he doused them with water weeks later, they unfolded their bodies and “came alive”.

 

Today, almost all biologists are resurrectionists. Flies, bacteria and some fungi have all shown this property. Not just that, the period for which they can stay “dead” before resurrection can be huge. A flower called narrow-leafed campion came to the surface after being buried under ice for over 30,000 years in the Ice Age. With careful nurturing, scientists could revive it to grow and produce seeds.

 

You may be thinking this may not be resurrection. Perhaps it’s just hibernation, except for much longer periods than what bears can do? The one-word answer why scientists don’t think that this is hibernation – water:

“When a cell loses water, chemical reactions grind to a halt. Its proteins stick together and form toxic clumps, while its membranes turn to sticky jelly.”

Most of the examples above lost all their water. If the cell can’t carry out any of the normal things cells do, surely it is dead, right? But then, when hydrated again, whatever it is doing should be called, er, coming back to life.

 

Or perhaps, there’s a third state – alive, dead, and whatever everything described above falls into. Yes, scientists have a name for this third state – cryptobiosis. This third state, cryptobiosis, isn’t just about resistance to dehydration.

“They can also survive in outer space.”

In 2007, scientists collected tardigrades, dried them out, and sent them to space on a rocket. For ten days, they were exposed to the vacuum of space.

“Back on Earth, a splash of water resurrected them.”

 

I found this is amazing. There aren’t just two states – alive and dead. There’s a third one too! And Zimmer was just getting started with all the weirdness of that seemingly obvious thing called “life”. More in the blogs to follow.