Biological clocks and regulation of seasonal reproduction and migration in birds.
Kumar, Vinod; Wingfield, John C.; Dawson, Alistair; Ramenofsky, Marilyn; Ranee, Sangeeta; Bartell, Paul. 2010 Biological clocks and regulation of seasonal reproduction and migration in birds. Physiological and Biochemical Zoology, 83. 827-835. 10.1086/652243Before downloading, please read NORA policies.
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Time-keeping is important at two levels; to time changes in physiology and behavior within each day and within each year. For the former, birds have a system of at least three independent circadian clocks present in the retina of the eyes, the pineal gland, and the hypothalamus. This differs from the situation in mammals in which the input, pacemaker and output are localized in different structures. Each bird clock interacts with at least one other clock and together, they appear to form a centralized clock system that keeps daily time. These clocks have a powerful endogenous component and the daily light-dark cycle entrains them to 24 hours. The timing and duration of life history stages that make up annual cycle of an individual must also be controlled by some form of time-keeping. However, evidence for the existence of an equivalent endogenous circannual clock is less clear. Environmental cues, particularly photoperiod, appear to have a more direct role than simply entraining the clock to calendar time. For example, the timing of migration is probably greatly influenced by photoperiod but its manifestation each day, as Zugunruhe, appears to be under circadian control. Migration involves marked changes in physiology to cope with the energetic demands. There is still much that we do not know about how organisms’ timekeeping systems respond to their natural environment, particularly how salient signals from the environment are perceived and then transduced into appropriately timed biological functions. However, given that changes in environmental input affects the clock, increasing human disturbance of the environment is likely to adversely affect these systems.
|Programmes:||CEH Topics & Objectives 2009 onwards > Biodiversity > BD Topic 2 - Ecological Processes in the Environment > BD - 2.4 - Estimate the impact of the main drivers and pressures on biodiversity ...|
|NORA Subject Terms:||Zoology
Ecology and Environment
|Date made live:||28 Sep 2010 08:56|
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