Biological timing Flashcards
Circa-annual
yearly cycles
Circadian
Daily cycles
Circa-lunar
Responses related to the moon/monthly
Biorhythm
A cycle of events that is controlled endogenously (genetically)
Benefits of biological clocks
- Allow prediction of events necessary for a build-up of food or reserves
- Synchronization of internal physiological processes
- Synchronization of social activities
- Allow for growth and development
Photoperiodism
Response to changes in day length by making appropriate physiological changes - in plants
Advantages of photoperiodism
Synchronises with ideal season for flowering, leaf fall and germination
Pr
Phytochrome red absorbs sunlight (mostly red light)
Pfr
Phytochrome far red absorbs night light (far red light)
Short day plants
- Require a short day and a long night
- Produce flowers only if the photoperiod (day length) is less than a critical length
- Flower in winter
Long day plants
-Require a long day and a short night
- Produce flowers only if the photo period that exceeds a certain critical length
- Flower in summer
When Pr absorbs red light
Quickly changed to Pfr
Endogenous
Something that is controlled internally/genetically
Exogenous
Controlled externally by zeitgebers or environmental cues
Zeitgebers
- ‘Time giver’
- Environmental cue which can change/train the internal clock, prompts us
Entrainment
Use of zeitgebers to change your internal clock, by resetting it to match environmental cues
Zeitgebers that control circaannual
Seasons, photoperiod
Zeitgebers that control circadian
Temperature, humidity, light, sound
Zeitgebers that control circatidal
Ocean movements
Pfr is unstable in night, what happens
Slowly reverts back to Pr
Lots of Pr means
Night is long
Not much of Pr means
Night is short
When there is a flash in the night what happens
Pfr is quickly converted as mistaken for short night, resets the plants counter of how long night is - short day plants won’t flower
Period of a rhythm
Time it takes to complete one entire wake/sleep cycle - generally 24 hours
Photoperiod rhythms are controlled by-
Pienal gland behind the eye and the suprachiasmatic nuclei (SCN)
Phase shift
When onset of the period of the rhythm is changed - normally due to removal of zeitgebers
Biological clock is made up of
Suprachiasmatic nuclei (SCN) at the base of the brain
When light intensity is low/high (biological clock)
eye detects less/more light and send messages to SCN which triggers the pineal gland to release more/less melatonin - controls the circadian rhythm
Diurnal
Active during the day
Nocturnal
Active during the night
