These include breeding behavior in a range of animals, the control of flowering and the induction of winter dormancy in many plants, and the operational control of the human immune system. In many of these biological processes the critical point is the length of the dark period rather than that of the light. For example, "short-day" and "long-day" plants are, in fact, "long-night" and "short-night" respectively.
These comprise breeding behavior in diverse animals, floral regulation and dormancy induction in numerous plants, and immune system management in humans. The critical factor in many of these biological processes is typically the darkness duration rather than the light duration. For example, "short-day" and "long-day" plants are actually "long-night" and "short-night" plants.