Here Marcus and Pann, you guys might like this. How tetrapods (4 legged creatures) came from the sea:
The origin of tetrapods
Insects and fish are some of the oldest life forms of the planet, I mean sharks were around before even the dinosaurs. Insects are even older than fish, but they too probably came from the sea, evolving from very, very early forms of shrimp, plankton and trilobites. Some think that they evolved from very early segmented worms or water bears (tardigrade).
Incidently, "water bears" are probably the toughest life form on the planet as this video will show:
Taken from wikipedia:
Tardigrades are able to survive in extreme environments that would kill almost any other animal. The following are extremes states Tradigrades can survive:
Temperature – Tardigrades can survive being heated for a few minutes to 151 °C (424 K or 304 F),[21] or being chilled for days at −200 °C (73 K or -328 F),[21] or some can survive temperatures for a few minutes at −273 °C (~1 degree above absolute zero/0 Kelvin or -458 F).[22]
Pressure – they can withstand the extremely low pressure of a vacuum and also very high pressures, more than 1,200 times atmospheric pressure. Tardigrades can survive the vacuum of open space and solar radiation combined for at least 10 days.[23] Some species can also withstand pressure of 6,000 atmospheres, which is nearly six times the pressure of water in the deepest ocean trench, the Mariana trench.[13]
Dehydration – although there is one report of a leg movement in a 120-year-old specimen from dried moss,[24] this is not generally considered "survival",[25] and the longest tardigrades have been shown to survive in a dry state is nearly 10 years.[26][27] When exposed to extremely low temperatures, their body composition goes from 85% water to only 3%. As water expands upon freezing, dehydration ensures the tardigrades do not get ripped apart by the freezing ice (as waterless tissues cannot freeze).[28]
Radiation – tardigrades can withstand 1,000 times more radiation than other animals,[29] median lethal doses of 5,000 Gy (of gamma-rays) and 6,200 Gy (of heavy ions) in hydrated animals (5 to 10 Gy could be fatal to a human).[30] The only explanation found in earlier experiments for this ability was that their lowered water state provides fewer reactants for the ionizing radiation.[31] However, subsequent research found that tardigrades, when hydrated, still remain highly resistant to shortwave UV radiation in comparison to other animals, and that one factor for this is their ability to efficiently repair damage to their DNA resulting from that exposure.[32]
Environmental toxins – tardigrades can undergo chemobiosis—a cryptobiotic response to high levels of environmental toxins. However, these laboratory results have yet to be verified.[24][25]
Outer space – Tardigrades are the first known animal to survive in Space. Since September 2007, Tardigrades were taken into low Earth orbit on the FOTON-M3 mission and for 10 days were exposed to the vacuum of space from which they returned alive.[33][34] After being rehydrated back on Earth, over 68% of the subjects protected from high-energy UV radiation survived and many of these produced viable embryos, and a handful had survived full exposure to solar radiation.[23][35] In May 2011, Italian scientists sent tardigrades into space along with other extremophiles on STS-134, the final flight of Space Shuttle Endeavour.[36][37][38]
Their conclusion was that microgravity and cosmic radiation "did not significantly affect survival of tardigrades in flight, confirming that tardigrades represent a useful animal for space research."[39] In November 2011, they were among the organisms to be sent by the US-based Planetary Society on the Russian Fobos-Grunt mission's Living Interplanetary Flight Experiment to Phobos; however, the launch failed.
This life form is over 500 million years old, making it one of the oldest on earth, and it's super tough resilience is probably what enabled the species to survive the 5 mass extinctions that have hit the planet. They will likely outlive humans, even if we destroy much of the planet in nuclear war.
Originally Posted by panntastic
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