1. The biological clock is evolutionarily advantageous because it allows organisms to anticipate changes in conditions before they occur. Since changes in gene expression are quite slow, organisms that can avoid this lag between stimulus and response are at an advantage.
  2. Phytochrome senses the light of daybreak. This is (somehow) transduced to activate LHY/CCA1 transcription. LHY/CCA1 reset the oscillator by activating morning genes, and repressing any TOC1 that was being expressed.
  3. Short-day plants can easily be explained by a flowering-inhibitor that has circadian rhythms of sensitivity. Short day plants flower when the amount of inhibition drops below a threshold limit, as daybreak falls ever later.

    Short day flowering can be explained by the involvement of a flowering inhibitor that has circadian rhythms of sensitivity