What eliminated the frontier in America

The fact of isolationism and they had already purchased Hawaii and Alaska, the manifest destiny was about moving west, when you are too far west you can’t go west or else your drown in Pacific Ocean

Hi! after fertilization occurs, the zygote goes through mitosis and then differentiation (aka specialization of cells) to have a variety of cells that perform different functions. this allows for the creation of tissues and so on, all of which were once stem cells with no specific function.i hope i !