Which term refers to organisms that are active at dawn and dusk?

The term that refers to organisms that are active at dawn and dusk is "crepuscular." This term specifically describes animals that are most active during the twilight periods of daybreak and sunset. This behavior helps these organisms avoid the heat of the day and the increased predation risks that may occur at other times.

In contrast, diurnal organisms are active during daylight hours, while nocturnal organisms are active at night. Long day plants, which are not relevant to periods of activity, specifically refer to plants that require longer daylight hours to flower. Thus, "crepuscular" accurately captures the unique pattern of activity that occurs at dawn and dusk.