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 encompass various biological aspects such as breeding behavior in different species, floral control and dormancy induction in many plant types, and immune system regulation in humans. In these biological processes, the length of darkness often takes precedence over the duration of light. For instance, "short-day" and "long-day" plants are actually "long-night" and "short-night" plants.