Earth spins as it orbits its energy source.
Because of the tilt of the daily spinning Earth, and its elliptical orbit as it spirals yearly around the Sun (following the Sun through Space, around the Galaxy), each place on the planet’s spherical surface receives differing amounts of energy throughout the day, and throughout the year.
This difference in energy reception has resulted in a pattern of life in plants that is seasonally regenerative. It is the reason behind seasonal migrations of birds, fish, and caribou. Energy flow influences the availability of food, requirements for warmth (thickness of animals’ coats), and usually influences times of mating and birthing.
Here Comes the Sun: A tutorial on why there are Seasons, with good animations.
“We are indeed aboard an 8,000-mile-diameter spherical space vehicle – Spaceship Earth.” “Everyone on board our Spaceship Earth can live abundantly and successfully on an ecologically sustainable basis. Humanity has the option to make it.”
– R. Buckminster Fuller
Calculate any size model of the solar system: Want some insight as to how far away fom the Sun we are? Build a scale model of the solar system. As you do so, think of the energy emitting in all directions from the Sun. Planet Earth receives about 2 billionths of that energy.