Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the main source of energy for living organisms in Earth?

### Response:
The main source of energy for living organisms on Earth is the sun. Energy from the sun is captured by plants in a process called photosynthesis, which converts energy from the sun into chemical energy found in food. This energy is then used by animals to fuel activities such as movement and metabolism.