All systems lose energy and tend to lose order. Energy must move from one place to another- at each transfer there is loss Much of this loss is heat and is due to friction. Friction is our friend. The primary energy source on this planet is the sun.
Energy flows downhill to Earth.
Living systems called organisms survive by capturing energy to maintain an equilibrium against the loss. Organisms called producers capture a small fraction of the solar energy and store it in complex carbon based molecules they construct from smaller molecules. They break down those molecules to release the energy for their use. Other creatures called consumers get their energy by eating producers or other consumers and taking their energy rich molecules. Without the struggle to acquire energy and store it there can be no life.