Biomagnification
Toxins build up as they move up a food chain.
About this topic
Biomagnification is the increase in concentration of a toxin at each higher level of a food chain. Persistent substances that aren't broken down or excreted, such as DDT and mercury, accumulate in fatty tissue. Small organisms contain a little, and predators eating many prey accumulate much more.
The key properties of such toxins are that they are persistent, fat-soluble and not easily excreted. Because each predator eats many prey and only about 10% of energy is passed on, the toxin is concentrated in smaller amounts of body mass. Bioaccumulation refers to build-up in one organism over time, while biomagnification refers to the increase through the food chain.
In the 1960s Rachel Carson's book Silent Spring warned that DDT sprayed on crops washed into water and concentrated through plankton, fish and fish-eating birds such as ospreys and bald eagles, whose eggshells became thin and broke. Bans helped these birds recover. Mercury in tuna, for the same reason, leads to advice that pregnant women limit large fish.
Reducing use of persistent chemicals protects top predators, including humans. A common error is thinking the toxin is more concentrated in water than in the animals; the opposite is true. Also, biomagnification affects top consumers most, not producers.
Key ideas
- Fat-soluble poisons are not excreted
- Top predators carry the highest levels
- DDT harmed eagles and falcons
Quick check
Use cases: where Biomagnification helps
- Homework: review the key idea behind Biomagnification before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Biomagnification without notes.
- Visual learning: play with the interactive lab to see how Biomagnification changes when you adjust its inputs.
- Teaching a friend: explain Biomagnification in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Biomagnification?
Toxins build up as they move up a food chain.
What will I learn in Biomagnification?
Fat-soluble poisons are not excreted. Top predators carry the highest levels. DDT harmed eagles and falcons.
Is Biomagnification part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Biomagnification lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Biomagnification?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.