Explain the origin and development of each of the various blood cells. Refer specifically to the bone marrow and the spleen.

idk let me see fdfdgdg

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.