Plants in Time

• Environmental displays / Regular Cycle may based on the movement of earth and the moon
• Cycles may includes

  Day & Night Cycles

  Seasonal Cycles

  Changes in gay length (Photoperiodism )

  Temperature

  Gravitational pull of the moon - High / Low tides
• Activity patterns are innate (genetically programmed) - controlled by internal clocks (Biological Clocks)
• Internal clock are mainly controlled by Zeitgeber (environmental cue)

  Synchronised by cues to determine time onset (Offset) of activity

  E.g. = Morepork starts to become active at nightfall
• Entrainment is that organisms activity is et to a specific zeitgeber - most common on set of daylight

  Chnages in season = Photoperiod (period of light - time of the day)
• Entrainment:

  Endogenous (Internal ) = Activity rhythms is under the control of internal clock = Displays characteristics period.

  Clock may still be able to run - still displays rhytmic activity
• Free running period is a a constant period typically not 24 hrs

  If > 24 hrs - activity occurs LATER each day

  If < 24 hrs - activity occurs EARLIER each day

  
• Endogenous Rhythms:

  Circadian - 24 hrs

  Circannual - 365 days

  Circatidal - 12 hrs / one tide

  Circalunar - 30 days

  Circa semilunar - 15 days
• Exogenous are external factors like photosynthesis = only occurs when there is a sufficient light intensity
• To determine between Exogenous and Endogenous

  if activity is put in constant / displays periodicity - if its affected by zeitgeber (on / offset ) of light - it may start to undergo phaseshift - it will start the activity until it coincides with the zeitgeber onset to be synchronised / entrained

  
  

  E.g. When travelling to different time zones
• Actogram :

  Normal Zeitgeber - entrained to onset darkness

  Shifts backward by 12 hrs offset activities moves back each day <24 hrs = earlier each day (phase shift)

  will take time to get synchronised agains - entrainments - (phase shift takes time )

  May remove zeitgeber leading to free running period

  
• Internal Clock are under genetic control by several genes
• In humans (internal clock ) daylight is detected by the eyes -> SCN (Hypothalamus --> Constantly needed to reset to entrain to 24hr

  Using day lights as zeitgeber
• Excellence:

  Adaptive adv. = Activity contolled by Env. Cues -> Entrains Internal Clock

  I.C = allow us to anticipate

  Predict onset favourable conditions = Gaining max Adv.
• E:

  Advantage includes :

  Being on time in Feeding

  Allow Animal to prepare for activities = migration = Increase breeding success

  Activities - become synchronised with favourable environmental conditions = Higher survival = Higher REP. success

  They become synchornised with other speices - increase mating and reproduction
• E:

  Synchromisation may occur between species -

  eg. Flower will open when pollinators are active

  + Pollinations = + Feeding

  Positive feedback relationship