Summary
The feeding position of an organism in a food chain, from producers upward.
In depth
Level 1 is producers, 2 primary consumers and so on. Some organisms occupy several levels. Biomass and numbers often decrease with level.
Trophic efficiency averages around 10 percent but ranges from 5 to 20 percent.
Assigning fractional trophic levels reflects omnivory. Fish stocks' mean trophic level can show fishing down the food web. Biomass pyramids can be inverted in the open ocean.
Key idea: trophic level equals the number of energy transfers from the producer plus one.
Trophic level can be estimated using nitrogen isotopes: the heavy isotope N-15 rises by about 3 to 4 parts per thousand at each step. Fractional trophic levels, such as 3.4 for a fish that eats both herbivores and carnivores, describe omnivores. Trophic efficiency varies: about 10 percent on average, with 5 to 20 percent from endotherms to ectotherms, since warm-blooded animals spend more on heat.
Not all production passes upward: plant material is often unpalatable or indigestible, and respiration consumes a large share at every level. Bottom-up control is where resources limit each level, and top-down control is where predators limit those below.
Example: marine mammals feeding on krill are at low trophic levels, so they find more energy than if they ate fish.
Frequently asked questions
What is Trophic Levels?
The feeding position of an organism in a food chain, from producers upward.
Which area of biology covers Trophic Levels, and how advanced is it?
Trophic Levels is one of the 54 topics in Ecology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Energy Pyramid, Consumers, Food Chain.
Can you give an example of Trophic Levels?
A human eating bread is at level 2, while eating a tuna is at level 4 or 5.
What should I learn before Trophic Levels?
Trophic Levels is a Beginner topic, so no earlier topic is required. Other Beginner topics in Ecology that pair well with it include Ecology, Ecosystem, Biotic and Abiotic Factors.
What topics are related to Trophic Levels?
The closest topics to Trophic Levels are Energy Pyramid, Consumers, Food Chain, Primary Productivity. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Trophic Levels?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Trophic Levels. To practise the whole of Ecology, use the Ecology quiz.
How is Trophic Levels different from Energy Pyramid?
Trophic Levels: The feeding position of an organism in a food chain, from producers upward. Energy Pyramid: Shows that only about ten percent of energy passes from one trophic level to the next. Read both side by side and note what each one explains.
How should I study Trophic Levels 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 Energy Pyramid and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.