What biological process powers the universe?

Explanation:

Energy from the Sun fuels life on Earth

The continual input of energy, mostly from sunlight, sustains the process of life. Sunlight allows plants, algae and cyanobacteria to use photosynthesis to convert carbon dioxide and water into organic compounds like carbohydrates. This process is the fundamental source of organic material in the biosphere. There are a few exceptions to this, such as ecosystems living around hydrothermal vents on the ocean floor, which derive their energy from the chemical compounds such as methane and hydrogen sulfide. In either case, the overall productivity of an ecosystem is controlled by the total energy available.

Energy flows through all life on Earth

Food web

Diagram of a food chain for waterbirds of the Chesapeake Bay. Image from US Geological Survey.[reuse info]Food webs show how energy moves throughout a system. Plants use energy from the Sun to create organic matter. Plants are then eaten by primary consumers who are in turn eaten by secondary consumers, and so on. In each step, the energy that was originally emitted by the Sun is consumed, but that energy also dissipates with each step. Animals use up 90% of the energy contained in the foods they eat for their normal activities. This leaves just 10% of the original energy available for the next consumer. The efficiency of the food chain decreases as you go upward. (Learn more about the transfer of energy in the food chain.)

This points out a critical factor in the distribution of energy in human foods too. Eating producers (plants) at the bottom of the food chain is the most efficient way for humans to acquire energy for living. This has implications for humans as we strive to keep a growing human population adequately nourished.

These ideas also introduce the origin of organic matter that later can become fossil fuels. The original source of energy in fossil fuels is sunlight, which fueled photosynthesis. Oil and natural gas come from photosynthetic plankton, which have been preserved in sediments on the ocean floor, heated, and chemically altered into hydrocarbons. Coal comes from plants that have been buried in sediment, compacted, and preserved. These ideas are further explored in Energy Principle 4. (Learn more about where oil comes from.)