  Photosynthetic life requires sufficient photosynthetically active radiation
(PAR) to metabolise. On Earth, plant behaviour, physiology and metabolism are
sculpted around the night-day cycle by an endogenous biological circadian
clock.
  The evolution of life was influenced by the Earth-Sun orbital dynamic, which
generates the photo-environment incident on the planetary surface. In this work
the unusual photo-environment of an Earth-like planet (ELP) in 3:2 spin orbit
resonance is explored. Photo-environments on the ELP are longitudinally
differentiated, in addition to differentiations relating to latitude and depth
(for aquatic organisms) which are familiar on Earth. The light environment on
such a planet could be compatible with Earth's photosynthetic life although the
threat of atmospheric freeze-out and prolonged periods of darkness would
present significant challenges. We emphasise the relationship between the
evolution of life on a planetary body with its orbital dynamics.
