yöllisyys

Yöllisyys refers to a nocturnal disposition, a tendency for an individual or animal to be most active during the night. This biological phenomenon is often associated with circadian rhythms, the internal biological clocks that regulate sleep-wake cycles and other physiological processes over a 24-hour period. Organisms exhibiting yöllisyys are adapted to thrive in low-light conditions, often possessing enhanced senses like night vision, a keen sense of smell, or acute hearing to navigate and hunt.

The evolutionary advantages of yöllisyys are varied. For some species, being active at night reduces competition for resources and offers a degree of protection from diurnal predators. For others, the cooler temperatures of the night may be more favorable for their physiological needs. Many common animals, including owls, bats, hedgehogs, and foxes, are well-known for their nocturnal habits. In humans, yöllisyys is often referred to as being a "night owl," a preference for staying up late and waking up later in the day. While often viewed as a lifestyle choice, extreme forms of sleep-wake phase disorders can have underlying biological components. The specific adaptations and behaviors associated with yöllisyys are diverse and depend heavily on the species and its ecological niche.