Both maternal and paternal ages are increasing in the developed world. The average age of mothers at time of childbirth has increased from 26.4 years in 1974 to 29.3 years in 2002, while the average age of fathers has increased from 29.2 years in 1980 to 32.1 years in 2002 [1]. This increase in the average parental age is most likely due to the societal trend for couples to delay starting a fam...

This quasi-experimental research investigates developmental regulation around a critical life-span transition, the "biological clock" for childbearing. The action-phase model of developmental regulation proposes contrasting control orientations in individuals approaching versus those having passed a developmental deadline. Individuals in an urgency phase close to the deadline should be invested...

The biological world is not static: organisms inhabit environments which change predictably over the course of the day and night. There will therefore be selective advantage to any individuals able to anticipate these changes and attune their physiology and behaviour accordingly. Anticipation of daily cycles is conferred by endogenous timers, biological clocks with an intrinsic period of approx...

It is beyond doubt that the timing of sleep is under control of the circadian pacemaker. Humans are a diurnal species; they sleep mostly at night, and they do so at approximately 24-h intervals. If they do not adhere to this general pattern, for instance when working night shifts or when travelling across time zones, they experience the stubborn influence of their circadian clock. In recent yea...

Circadian clocks are thought to enhance the fitness of organisms by improving their ability to adapt to extrinsic influences, specifically daily changes in environmental factors such as light, temperature, and humidity. Some investigators have proposed that circadian clocks provide an additional "intrinsic adaptive value," that is, the circadian clock that regulates the timing of internal event...

Tanya Leise ([email protected]) received her Ph.D. from Texas A&M University and is captivated by applied mathematics in many contexts, from accelerating cracks to biological clocks. Of particular interest to her recently has been the mathematics of mechanical devices such as astrolabes and planimeters, which are also great fun to collect. When not doing math, she enjoys cycling and sewing stu...

A crucial property of the brain is to integrate temporal information with accurate physiological responses (Hinton and Meck, 1997; Buhusi and Meck, 2005; Coull et al., 2011). Evolution has favored biological clocks that dictate homeostatic processes (e.g., the circadian timing of sleep) and, on a smaller time-scale, timed behavioral responses (e.g., interval timing). The interplay between such ...

Circadian clocks allow the temporal compartmentalization of biological processes. In Arabidopsis, circadian rhythms display organ specificity but the underlying molecular causes have not been identified. We investigated the mechanisms responsible for the similarities and differences between the clocks of mature shoots and roots in constant conditions and in light : dark cycles. We developed an ...

BACKGROUND Circadian rhythms regulate many physiological, behavioral and reproductive processes. These rhythms are often controlled by light, and daily cycles of solar illumination entrain many clock regulated processes. In scleractinian corals a number of different processes and behaviors are associated with specific periods of solar illumination or non-illumination--for example, skeletal depo...