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Image
of Mars: NASA
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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.
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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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