- Life Processes need gases or other dissolved substances before they can happen such as photosynthesis that needs oxygen and carbon dioxide. As well as respiration needing glucose and oxygen. These substances need to get into the cells of the organism.
- Waste substances also need to be move out of the cell
There are three different methods needed for this take place:
- Diffusion- the movement of particles from a high concentration to a low concentration- dissolved particles moving in and out of cells through cell membranes
- Osmosis- The movement of water molecules across a partially permeable membrane from a high concentration to a low concentration
- Active Transport- The movement of particles from an area of low concentration to a high concentration (against the concentration gradient).