In contrast, photoautotrophs, i.e.
photosynthetic organisms such as plants and algae, use the energy of sunlight (photo = sunlight) to synthesize the carbon compounds they need to grow and reproduce.
For a
photosynthetic organism — one that uses light as an energy source —
such as the green alga Chlamydomonas reinhardtii, keeping in sync with day and night is a particularly important ability.