Page 84 - Engineering in Nature

Engineering in Nature

nerve fiber and after a short distance, the three fibers join and fibers
continue on to the moth's central nervous system, combined, as the
middle ear nerve.
Electrical signals in the nerve fibers carry an electrical charge of
th
1/2000 of a volt. The signals in the moth's A fibers reach the central
th
nervous system from the sensory cells in as little as 1/2000 of a sec-
ond.
These nerves have the capacity to perceive the sound waves that
bats emit. Moreover, they are very sensitive when it comes to identi-
fying the magnitude of their waves and the changes between them.
Thanks to all these features, the moth can distinguish between the
squeaks of a distant bat from the louder, stronger ones approaching to
catch it. 26

• How Do Moths Make This Distinction?
To answer that question, scientists started by determining which
information reaching the ear the moth analyzes, and how it arrives at
an interpretation. Some of the details they discovered eliminate the
evolutionists' "random changes" claim:
Scientists took measurements with an oscilloscope, which registers
microscopic electrical currents. When a bat squeak stimulates the
moth ear, liquid levels in the oscilloscope reveal that the A cell imme-
diately goes into action. As the signal's strength increases, changes are
observed. First the magnitude of the signals rises, then the time lag
between them falls. Rises are observed in both A fibers at once,
though the A1 fiber is more sensitive to sound than the A2 fiber. And
the greater the intensity of the signal, the faster the A cell produces a
rise.

To scientists analyzing this information, new questions await. In

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