NCSU Course ZO410 Lecture:

Biological Timekeeping

Animal Behavior over Time
Consolidation of behavior across the day, season, etc.
By being Diurnal, Nocturnal or Crepuscular animals are exposed to a more narrow range of conditions.

Why have a clock?
    Anticipation of environmental changes
    Coordination of internal processes
    Measurement of cyclic events

Environmental cyclicities
    Daily
    Monthly
    Tidal
    Annual

Daily Rhythms v/s Circadian Rhythms
de Marian 1729

Internal Clocks:
Step 1 - How does one measure a clock?

Clock Characteristics

Rhythms are entrainable by ZEITGEBERS (Time cues).
Rhythms are endogenous.
Rhythms have a periodicity close to that of the external cycle it attempts to time.
Rhythms are temperature compensated.

Location of Biological Clocks in Vertebrates (pacemaker versus clock)
Mammals

SCN (suprachiasmatic nucleus of the hypothalamus)
Classic studies - Lesion, Transplant
Tau Mutant Hamster

Non-Mammalian Vertebrates

Pineal gland
Classic studies

Light cues in Mammals versus Non-Mammalian Vertebrates

Eyes
Pineal (not photoreceptive in mammals)
Extraretinal Photoreceptors (not present in mammals)

Melatonin
Peaks at night in almost all animals
Transducer of photoperiod in mammals

Annual Rhythms
Circannual versus Photoperiodism

Humans and Circadian Rhythms
    Examples of Rhythms
    Jet-Lag
    Shift-work
    Sleep

Circalunar
Ant-Lion

Circatidal

End of Lecture-Biological Timekeeping subsite. Move to: ZO 410's Course Homesite.

Original author this subsite (lbtk.html)= calswww@ncsu.edu, originally posted 10-17-2001.