Active transport is the <span>method of material exchange uses up energy.</span>
They concluded that horses evolved with the emergence of grasslands and an increase of predators. The digits of their early Eocene ancestor evolved into hooves.
All cells have cell membranes, and the membranes are flexible. So animal cells can have various shapes, but plant cells only have the shapes of their cell walls. That's nice for plants, because it gives them the ability to grow up and out, where they can get lots of sunlight for making their food.
