The natural phenomenon responsible for the seasons on Earth is the tilt of the Earth's axis relative to its orbit around the Sun. This axial tilt, approximately 23.5 degrees, leads to varying angles of sunlight and changing daylight durations throughout the year. As the Earth orbits the Sun, different regions experience different seasons, such as summer and winter. This cyclical change in seasons affects climate, weather patterns, and ecosystems worldwide, influencing phenomena like plant flowering and animal behavior.