Summary
Energy enters from the sun, flows through food chains and is lost as heat at each step.
In depth
Light is captured by producers; only about 1 percent of incident sunlight ends up as chemical energy. At each trophic level around 90 percent is lost as heat.
Energy is not recycled; it flows through and leaves as heat. Efficiency of use differs between ectotherms and endotherms.
Key idea: sunlight is the primary energy source for most ecosystems.
Energy flows one way through ecosystems: sunlight is fixed by producers as chemical energy (gross primary production); some is used for the producers' own respiration, the rest is net primary production available to consumers. Energy passes to herbivores, carnivores and decomposers.
At each trophic level only about 10 percent is transferred (range 5 to 20), because of respiration, heat, waste and uneaten parts. This explains why food chains are short and why biomass and energy pyramids are narrow at the top. Nutrients, by contrast, cycle.
Example: eating plants directly supports more people per hectare than eating meat from grazing animals.
Common mistake: energy is not recycled; it is lost as heat.
Frequently asked questions
What is Energy Flow in Ecosystems?
Energy enters from the sun, flows through food chains and is lost as heat at each step.
Which area of biology covers Energy Flow in Ecosystems, and how advanced is it?
Energy Flow in Ecosystems is one of the 53 topics in Metabolism & Bioenergetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Photosynthesis vs Respiration, ATP, Cellular Respiration.
Can you give an example of Energy Flow in Ecosystems?
Ecosystems need a constant supply of solar energy because energy cannot be recycled.
What should I learn before Energy Flow in Ecosystems?
Energy Flow in Ecosystems is a Beginner topic, so no earlier topic is required. Other Beginner topics in Metabolism & Bioenergetics that pair well with it include Metabolism, Anabolism and Catabolism, ATP.
What topics are related to Energy Flow in Ecosystems?
The closest topics to Energy Flow in Ecosystems are Photosynthesis vs Respiration, ATP, Cellular Respiration, Alcoholic Fermentation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Energy Flow in Ecosystems?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Energy Flow in Ecosystems. To practise the whole of Metabolism & Bioenergetics, use the Metabolism & Bioenergetics quiz.
How is Energy Flow in Ecosystems different from Photosynthesis vs Respiration?
Energy Flow in Ecosystems: Energy enters from the sun, flows through food chains and is lost as heat at each step. Photosynthesis vs Respiration: Photosynthesis stores energy in glucose and releases oxygen; respiration releases that energy and consumes oxygen. Read both side by side and note what each one explains.
What is a common mistake about Energy Flow in Ecosystems?
Energy is not recycled; it is lost as heat.
How should I study Energy Flow in Ecosystems step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Photosynthesis vs Respiration and explain the difference aloud. Finally, take the Metabolism & Bioenergetics quiz and come back to this page for any question you miss.