Esoteric Universe

June 22, 2011

What did the first life on Earth look like? Research into the oldest lineages of single-celled life suggest that the first life form on Earth would likely have been an extremophile that survived in the hydrothermal vents (233) at the bottom of the ocean floor; this organisms would have lived off of the gases spewing from the vents and could have survived in near-boiling water. This cell would have been an archean life form; its cell wall would have been built out of peptidoglycan or a similar chemical meant to survive such daunting pressures and the acidity of the dissolved hydrothermal vent gases. Acidophilic cell membranes like this would be designed to pump hydrogen ions out of the cell and maintain a more neutral pH than the environment of the vents. Only an extremophile could survive the early environments on Earth and Areios.

The metabolisms of all animals are very similar and involve the same metabolic pathway; oxidative respiration. But archean life has such an eclectic set of anaerobic metabolic pathways; some organisms breathe hydrogen sulfide gas that bubbles out of the hydrothermal vents at the bottom of the ocean. These organisms are cut off from the Sun and form the base of an ecosystem that is wholly independent of photosynthesis. This world relies on chemosynthesis; instead of a utilizing a photon to start the electron transport chain, these creatures harvest electrons from hydrogen sulfide to kick start the process. Organisms need not use hydrogen sulfide, though. Some creatures have been known to use molten iron, arsenate, methane, or hydrogen gas.

Areiosan life too relies on sulfur to power the electron transport chain. One flaw of this system is that it doesn’t release as much energy as oxidative respiration. Animals simply can’t function off of anaerobic respiration; only in the rarest cases can anything bigger than the simplest multicellular organisms. Yet, there are complex organisms on Earth that have found a way survive off of anerobic respiration. Tubeworms living near hydrothermal vents have chemosynthetic organisms lining their gut to thank for their providing food. These bacteria use the hydrogen sulfide from the vents to produce ATP that they feed to the tubeworms. This symbiotic relationship is exceptional on Earth, but on Areios, it all but proves to be the rule for any macroscopic life.

Giant tubeworms can thrive in these environments, stretching up to 3 meters long. These organisms are extreme even in their ability to develop and grow so rapidly. In two years, some specimens can grow almost 10 feet under ideal conditions. Few creatures on Areios are ever as big as that because rather than devoting all of that energy into growth, Areiosan life forms devote the energy from their internal bacteria into mobility and procreation, so they are on the whole much smaller than life on Earth. Not only is the climate on Areios across-the-board colder than on Earth, owing to the higher levels of sulfur dioxide, but gravity on Areios is more intense and this keeps any organisms from growing too tall because the pull of gravity would limit anything from growing too tall. Anything but the sturdiest creatures would buckle under the weight of the atmosphere. For now, life on Areios is nothing but pond scum and singular bacteria, but with the advent of oxygen, organisms can evolve into the complex forms we recognize as animals like the ones found on Earth.

Yet, the environment on Areios keeps the organisms we could identify as animals from growing to the size of some organisms we find on Earth. There are no blue whales or sequoias on Areios; the largest animal to trammel its surface is perhaps the size of a horse. Low oxygen and high sulfur levels limit the size an organisms can reach and because oxygen is so scarce, endothermic organisms like mammals and birds with such a high metabolism are unlikely to be able to survive on Areios because of how much energy they would require to maintain their high-maintenance, warm-blooded metabolisms. Yet the largest organisms on Areios are more akin to fungi or coral reefs, many-headed colonial organisms that spread out over huge geographic expanses In fact, because of this harsh environment animals don’t arrive on the scene until much later in the evolutionary history of Areios. It takes almost 10 billion years for anything complex more complex than our primordial extremophile to arise on Areios, and by then, these novel animals are only ephemeral; as soon as they arrive, they are wiped out 4 billion years later.

 

Deep under the ocean in hydrothermal vents, there is an entire ecosystem built off of chemosynthetic bacteria that feed on sulfides. This could indicate life need not rely on the light from a star, but could thrive in other extraterrestrial environments.

 

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3 Responses to “Esoteric Universe”

  1. Alex said

    Nice article! Where did you get the chemosynthesis picture? It is the best picture I have seen and I would like to use it for school, but I can’t site a blog. :\

    • hartm242 said

      Unfortunately, I can’t seem to find the site where I took this picture from either. Since I stopped blogging for this site, I’ve deleted or lost most of my files. I spent much of this morning searching for this pic again, but somehow the original is unavailable, too. I wish that I could be of more help, but I don’t know where I found this diagram to begin with.

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