Plant and Animal Responses Flashcards
Circadian Rhythm
- 24 hours (day-night cycle)
- Triggered by light availability
- Types: diurnal, nocturnal, crepuscular
- Advantage: predict daybreak, search for food early, maximise feeding
Circalunar Rhythm
- Approx. 295 days
- Advantage: predict spring tides for full moon, maximising % of successful reproduction
Circannual Rhythm
- Approx. 365
- Triggered by day length
- e.g. migration/hibernation of animals when leaves fall off trees
- Advantage: predict winter, moult summer hair, replace with longer winter hair for increased insulatiohn for colder temperatures
Circatidal Rhythm
- Approx. 12 hours, linked to changes in tides
- Tide in, organisms are submerged = feeding and reproduction
- Tide out, organisms exposed to air, dessication = activity stops
- Advantage: predict incoming tides = feed early etc.
Photoperiodism
Regulation of seasonal activity by day length, controlled by phytochromes
Phytochrome
Controls photoperiodism response, there are 2 types:
- Pr (day) and Pfr (night)
- During the day, Pr absorbs all red light from the sun, which is then converted to Pfr and vice versa
Long day plants
Flower in spring/summer (more Pr) e.g. sunflowers
Short day plants
Flower in autumn/winter e.g. spinach
Day neutral plants
Flower any time of year (not affected by day length)
Advantage of photoperiodism
Plants cannot move to favourable environments so instead change their rate of growth (to synchronise with pollinators)
Exogenous Rhythm
Externally driven (light availability, day length)
Endogenous Rhythm
Internally driven (internal body clock/superchiasmatic nuclei)
Zeitgeber
Environmental cues that reset the internal body clock/superchiasmatic nuclei
Free-running Period
When no zeitgebers are present
Entrainment
Resetting the superchiasmatic nuclei to match the environment
Actogram
Shows activity of organism during the day and changes in the environment
Phase Shifting
When time of activity/inactivity is pushed forwards or backwards
Benefits of biorhythms
- allows for the prediction of events that need a build up of food or reserves (migration)
- synchronisation of internal physiological processes and social activities
Taxis
Directional response either towards or away from a directional external stimulus e.g.
Kinesis
Non-directional response, rate of movement (activity influenced by an external stimulus) e.g.
Klino-kinesis
A change in rate of turning in organism
- Favourable environment = slower rate of turning
- Non-favourable environment = faster
Ortho-kinesis
A change in speed
- Favourable environment = slower
- Non-favourable environment = faster
Migration
Seasonal mass movement of a population from one location to another (for more food, better breeding conditions, away from predators/harmful weather)
Migration timings
Often triggered by biological rhythms (change in day length/climate - exogenous) and the body clock will prepare the animal for migration (endogenous rhythm)