Xylem carries water and dissolved nutrients
All elements of a ecosystem work together, the sun provides sun light which plants use photosynthesis for food. Small animals eat the producers aka the plants. Then other animals eat those. And so on if a plant wasn't alive then the whole ecosystem will fail.
Theories explain phenomena, whilst laws are generalizations which characterize them.
Coal is made up of carbon, so burning coal releases carbon
Because we do or we would die
