Energy & Feeding Relationships

Transfer of Energy

Where Energy Comes From

All energy in biological systems ultimately comes from the Sun. This is the foundation of every ecosystem on Earth. Without the Sun, no organism could survive.

Here's how it works:

• Plants (producers) capture light energy from the Sun and convert it into chemical energy stored in glucose through photosynthesis.
• Animals eat the plants and obtain this stored chemical energy. This energy is used to build new cells, move, reproduce, and maintain body temperature.
• Energy is eventually lost to the environment as heat through respiration, movement, and metabolic processes.
• Decomposers (bacteria, fungi) break down dead organisms and return nutrients to the soil while releasing energy as heat.

Energy is Not Recycled — It Flows One Way

This is a critical point: energy flows through an ecosystem but is not recycled. Unlike nutrients (carbon, nitrogen), energy enters as sunlight and leaves as heat. The Sun is continuously putting in new energy, so ecosystems don't run out — but organisms need that constant input.

Food Chains & Food Webs

Key Organisms & Their Roles