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Daily and Seasonal Timing

Circadian and Circannual Clocks in Living Things. Daily and Seasonal Timing. Many Living Things Have a Internal Clocks. DAILY. SEASONAL. Regulates seasonal changes in gene expression and behavior. Regulates daily cycle of activities. Circadian Rhythm are Endogenous.

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Daily and Seasonal Timing

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  1. Circadian and Circannual Clocks in Living Things Daily and Seasonal Timing

  2. Many Living Things Have a Internal Clocks DAILY SEASONAL Regulates seasonal changes in gene expression and behavior • Regulates daily cycle of activities

  3. Circadian Rhythm are Endogenous • Occur internally- do not require environmental cues • BUT can be altered by environmental cues

  4. Under Genetic Control • We have genes that control these rhythms • But environment can change gene expression

  5. Evolutionary Adaptations • Daily and seasonal changes are genetic characteristics that have evolved because their presence is advantageous • Natural selection has favored these traits

  6. Circadian Rhythms in Plants • Change in leaf orientation • Opening of stomata – pores in the leaf • Opening of flowers and release of fragrance

  7. Observations of Plants • Leaves happened at nearly same time every day, even on cloudy days • BUT artificial light at different times confuses the plant’s internal clock

  8. Circadian Rhythm in Animals • Closely tied to sleep-wake cycle

  9. Why You’re Stressed in the Morning

  10. Light Might Inhibit Melatonin Release • Melatonin thought to control sleep urges • Concerns artificial lights prevent melatonin release and keep people awake

  11. Seasonal Clocks • Affect gene expression • Control things like: • Shedding of coats • Reproduction • Hibernation • Migration

  12. Photoperiodism in Plants • Plants measure length of night • Certain night length triggers flowering

  13. How? • Light changes structure of phytochrome protein • Longer the darkness, the more Pr there is

  14. Short Day vs. Long Day Plants Flower in spring/summer

  15. In Animals • Light absorption by the eye triggers change in gene expression • Thought to be mediated by melatonin

  16. Shedding of Coats or Changing of Color • Arctic Wolf in Summer • Arctic Wolf in Winter

  17. Seasonal Reproduction • Many species only reproduce in spring or summer • When more food (energy) is abundant

  18. Ex. How Seasons Affect Reproduction in Animals

  19. Hibernation • Helps conserve energy when little food available

  20. Migration • Changes in light trigger hormone changes • As there’s less light birds build up fat for journey • BUT also occurs in birds in captivity with consistent light sources • BUT reducing light brings about changes in behavior

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