Origins ANTARCTICA, Scientific Journeys from McMurdo to the Pole
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Fish: Fresh, Not Frozen

Photo of Mars
  Image of Mars: NASA

A Laboratory for Extraterrestrial Life
Many scientists investigating adaptations in Antarctic "extremophile" creatures are not only interested in Earthly ecosystems. Their research may also offer clues about what organisms may live in similar extreme environments elsewhere in the solar system, such as Mars.

Scientists, for instance, have discovered microorganisms living in rocks collected from the Mars-like environment of the McMurdo Dry Valleys, considered the coldest and driest region on earth. They found that these creatures could live in a dormant state for thousands of years, regaining metabolic activity when thawed. If such life persists here, they contend, perhaps microorganisms with similar adaptations could survive on Mars.

In light of life’s impressive ability to adapt—from antifreeze fish to ancient bacteria in frozen rocks—such theories of extraterrestrial life seem remarkably rational.

The continental tear also separated the region’s fish populations, some migrating to warmer South American waters and others heading south to Antarctica. As Antarctic waters chilled, most of the southern migrants froze to death. Among the lone survivors in the mass extinction were the Notothenioids with antifreeze proteins.

At this point, an important change occurred in the Antarctic Notothenioid population. As the non-antifreeze-carrying Notothenioids disappeared, and the antifreeze-protected ones reproduced and expanded their numbers, the entire Notothenioid population eventually carried the antifreeze mutation.

A Textbook Evolutionary Adaptation
Ecologists point to the survival of the antifreeze-carrying Notothenioids in Antarctica—and their subsequent population growth—as a classic example of an evolutionary process called adaptation.

A population (group of organisms of the same species) usually adapts in two main stages.

First, there’s a random genetic change in a segment of a population that offers advantages in a new environment or climate. In this case, the antifreeze-protein mutation gave some Notothenioids a big edge in the colder waters.

Second, over millions of years, individuals with the special trait survive and pass the trait to later generations, while individuals without the trait die off. Eventually, the entire population has the favorable trait, as was the case with the antifreeze-carrying Notothenioids.

Adaptations fuel evolutionary change in nature—changes in how species move, eat, reproduce, defend themselves, and much more. These changes not only help species survive in new surroundings. They can also create new species—which brings us back to our tale of how the Notothenioids attained dominance in the Antarctic seas.


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