The energy used by all living organisms on earth can be traced back to the sun. The sun produces heat and light energy which helps in maintaining temperatures on earth and creates daylight. Plants, which are sometimes referred to as producers, use light energy in a process called photosynthesis to create nutrients or energy.
No organisms on earth can manufacture their own food except plants. Plants use carbon dioxide and light energy from the sun to create nutrients which act as energy for basic functions including growth and transportation. Animals that are classified as primary consumers get energy by eating plants. This means all the nutrients or energy that was created by plants is transferred to those animals that consume them.
On the next level are animals that eat primary consumers. These animals or secondary consumers also acquire energy from the plant eating animals. There are also animals called tertiary consumers which get energy by eating other animals and plants.
Living organisms like lions and leopards use energy for chasing down prey and fighting off enemies, while those within the depths of the sea may use energy to create their on light since sunlight is not able to penetrate to certain points.