The Living Clock

Virtually all living things, from single-cell plants and animals up through
humans, contain an organic timepiece within their protoplasm. This horologe
is used to adjust individual organisms behavior and physiology to the major
geophysical periodicities expressed in their habitats. Organisms most
commonly synchronize their activities to the twenty-four hour day-night
cycle, but some, like intertidal dwellers, also mimic the timing of the ebb
and flow of the tides.
The fundamental rate at which a clock runs is innate. Here are examples of
the proof for this. There are plants that raise their leaves during the
daytime and drop them to the sides of their stems at night. When these plants
are brought into the laboratory where the lights are always left on and the
temperature held constant, the leaves still rise and fall pretty much in
synchrony with those of their former neighbors remaining in the natural
setting outdoors. Intertidal crabs run around the shoreline when the tide is
out but remain in their burrows during high tides, and display the same
running/rest pattern in the constancy of the lab. Clearly, in the absence of
day/night and high/low tidal changes the experimental organisms clocks take
total temporal control.
The human clock is a daily one. People tested in aperiodic conditions in the
lab continue their same sleep/wake patterns thanks to their internal clocks.
Something like one hundred other processes in humans are known to be under
the same clock control.
While the period of the clock is innate, it s “hands”, i.e., the phase of
the overt activities driven by it, can be reset. This is accomplished by
moving an organism to a different time zone on the face of the earth. Human
shift work of does the same thing.
My talk will illustrate the basics of the temporal aspects of living things.