Diffusion is a passive process that does not require energy. It is the movement of molecules like gas or liquid from a region of a higher concentration to the region of a lower concentration, down the potential concentration gradient. For example: the diffusion of perfume in a room or the diffusion of the aroma of food from one area to another. In plants, carbon dioxide and oxygen diffuse into and out of the plant through stomata. Also gases diffuse during the exchange of gases. Osmosis is the movement of water molecules only and it is also a passive process. It involves the movement of water molecules from an area of higher water potential (where solute concentration is low) to the area of a lower water potential (where solute concentration is high). This happens across a semipermeable membrane, and also down the water potential gradient. For example: the movement of water molecules across a membrane along with salt molecules as the solute. A semipermeable membrane only allows some molecules to pass through; for instance, only water molecules can pass through it and not the larger solute molecules like sucrose. The different types of osmotic solutions are isotonic, hypertonic, and hypotonic. Isotonic solution has equal amount of solution concentration inside and outside the cell. Hypertonic solution has more solute concentration outside the cells as compared to the inside of cells. Hypotonic solution has less solute concentration outside the cells while more inside the cells. Active transport is an active process that needs energy in the form of ATP. It is the movement of particles from a region of lower concentration to a region of high concentration, against the concentration gradient. For example: there are transport proteins embedded in the membranes which use ATP to pump ions and amino acids. In plants, root hair cells uptake minerals using active transport from the soil. To wrap up: 