1989 kuller Ful reconstructed. why did the US government bring back the Spanish Flu?

1. is geographic distribution

2 is increasing complexity

3 is transitional forms

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.