annual rhythm

A biological rhythm is a periodic fluctuation in an organism that aligns with environmental changes, such as day/night cycles or tides. These rhythms are maintained by an internal "biological clock".1

A rhythm with a 24-hour cycle is called a circadian rhythm. Other rhythms include lunar tidal rhythms, which affect seashore life, and monthly rhythms seen in marine organisms. Annual rhythms are evident in the reproduction and growth of most terrestrial plants and animals.1

Many animals exhibit seasonal or rhythmical sexual reproduction and behavior, often timed for safety or to ensure the survival of offspring when environmental conditions are most favorable. For instance, birds and mammals often give birth in spring when food is plentiful. These cycles are regulated by hormones, influenced by factors like light and temperature.23