"Diurnal" refers to organisms or activities that occur during the daytime. Many animals, such as birds and squirrels, are diurnal, meaning they are active when the sun is up. This behavior helps them find food and avoid predators that may be more active at night. In contrast to diurnal species, there are nocturnal creatures that thrive in the dark, like owls and bats. The distinction between diurnal and nocturnal is important in understanding ecosystems and the behaviors of different species, as it influences their feeding patterns, mating rituals, and interactions with other organisms.