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Orientation in time
as part of AS91603 NCEA L3 Biology
| Term | Definition |
|---|---|
| actogram | An activity / time graph for an organism. |
| biological clock | An internal timing system in organisms. |
| circa- | Means ‘about / approximately’. ONLY used to describe internal rhythms occurring in constant environmental (free-running) conditions. |
| circa-annual | An internal rhythm of about one year can be observed in constant environmental (free-running) conditions. |
| circadian | An internal rhythm of activity/inactivity in about 24 hours can be observed in constant environmental (free-running) conditions. |
| circa-lunar | An internal rhythm of about one month can be observed in constant environmental (free-running) conditions. |
| circa-tidal | An internal rhythm of about 12.5 hours can be observed in constant environmental (free-running) conditions. |
| crepuscular | Most active at dawn and dusk. |
| critical day length | The photoperiod above which long-day plants flower, and below which short day plants will flower. NB: remember: later research discovered it’s actually the length of DARKNESS which is critical to the plant. |
| daily rhythm | Activity occurring every 24 hours (NB: zeitgeber(s) present!). |
| Day neutral plant | A plant that flowers independently of the day length. |
| diurnal | Most active during the day. |
| dormancy | A state of temporarily reduced metabolism in plants. |
| endogenous rhythm | Controlled by an internal timing mechanism (biological clock). It continues in the absence of environmental cues. |
| entrainment | Process by which the internal clock is reset so that it is synchronised with an environmental rhythm. |
| exogenous rhythm | Controlled by an external cue or stimulus. |
| free running period | The length of an organism's activity period in the absence of external cues (zeitgebers). |
| free-running | Occurring in the absence of environmental cues. |
| hibernation | A period of suspended activity / very low metabolic activity during winter, generally to survive a lack of food. |
| jet-lag | Condition caused when the endogenous circadian rhythm does not match external cues. Usually caused by travelling across time zones. |
| nocturnal | Most active at night. |
| period | The length of the activity cycle (how long it takes to repeat) of an organism. |
| phase shift | A change in the starting time of a rhythm (but not its period). |
| photoperiod | The day length; this is the most reliable indicator of time of the year. |
| photoperiodism | The control of seasonal activity by day/ usually night length. |
| phytochrome | A plant pigment that controls the photoperiodic response (measures the length of darkness / light). Comes in 2 forms, Pr and Pfr |
| short-day plant | A plant that flowers when the night length is greater than the critical length (i.e. short day). |
| long-day plant | A plant that flowers when the night length is shorter than the critical length (i.e. long day). |
| zeitgeber | The external environmental cue used to ‘set’ the biological clock. In most species, this is the change from light to dark (or dark to light). |
| suprachiasmatic nuclei (SCN) | A tiny region within the hypothalamus of the brain, connected by nerves to the eyes. Responsible for controlling the circadian rhythm in animals. |
Created by:
NZARoberts
Popular Ecology sets