AAPR Orientation in time - Animals

2. Active mainly around dawn and dusk.
6. Active mainly during daylight hours; this describes an activity pattern, not the period of the underlying biological rhythm.
7. The natural period of an endogenous rhythm when the organism is isolated from external time cues.
9. A biological rhythm with a period linked to the tidal cycle, commonly about 12.4 hours.
11. A graph showing an organism's activity and inactivity over successive time periods, commonly displayed across repeated 24-hour rows.
13. Synchronisation of an endogenous biological rhythm with an environmental cycle through repeated zeitgeber cues.
14. A biological rhythm with a period of about one year.
17. An endogenous biological rhythm with a period of about 24 hours.
19. A repeated response driven directly by an external environmental cycle rather than maintained by an internal clock.

1. Active mainly during the night.
3. gland An endocrine gland that secretes melatonin and helps coordinate daily and seasonal timing in many vertebrates.
4. nucleus The main circadian pacemaker in mammals; it receives information about light and coordinates daily rhythms.
5. A rhythm generated internally that continues without external timing cues.
8. A change in the timing of a rhythm so that its peaks, troughs or onset occur earlier or later.
10. An internal timing mechanism that generates and coordinates biological rhythms.
12. A biological rhythm with a period of about one lunar month (approximately 29.5 days).
15. The part of a daily cycle during which an organism is normally active, for example diurnal, nocturnal or crepuscular activity.
16. An environmental time cue, such as the light-dark cycle, that entrains a biological clock.
18. The time taken to complete one full cycle of a biological rhythm.