Answer:
this is because the continents where in diffrent positions then the outer most parts where more tropicle and the ferther you went into the mass the more it resembled a desert as the continents moved the plants started to change and adapt and the tropicle plants started to reduce to islands and some costal regions the continents eventualy had compleatly diffrent climats the northern and southern had always bin on oposite sides of seasons which gave the life on the planet room to evolve.
Explanation:
