In my opinion all of them apply (except the 4th one). Ecosystems can be small, big, have living and non-living parts and they are made of biomes. Not only can ecosystems vary in size, but they can also differ in just about every imaginable biotic or abiotic feature.
When the cell concentrates potassium within, against the natural tendency of matter, it is performing a.passive diffusion b.facilitated diffusion c.active transport d.pinocytosis