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>>JOHN SPARKS: A common thread
through the whole exhibit
"Life at the Limits" is
evolution, and specifically,
natural selection.
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>>MARK SIDDALL:
Life on this planet
lives within a very thin
region called the biosphere,
but it's amazing
how variable that
is in terms of temperature,
in terms of pressure,
in terms of different
environments--
wet, dry, hot, cold.
The animals and plants
that live in these places
didn't always live there,
and those environments
are changing.
>>SPARKS: Organisms within
a population have variation,
and they pass down this
information to their offspring.
If that information or
those characteristics
provides an advantage
to the offspring,
they're more likely
to survive, and those
that are more likely
to survive then
are more likely to reproduce.
Then that trait can spread
through the population
and become established.
So you get things spreading
through populations
that allow organisms to maybe
move into a new environment
and differentiate.
Think of a cave fish.
They tend to lose their eyes.
They don't need them anymore.
They lose their pigment.
It's costly to produce pigment.
So they're specifically
adapted to live
in a particular environment.
And that's why we see all
these spectacular forms,
because over a long
enough period of time,
these changes do spread
through populations.
They confer an advantage, and
you get all this diversity
that you'll see and you'll be
exposed to in this exhibition.
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