biological magnification


  1. the increasing concentration of toxic substances within each successive link in the food chain.


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More About Biological Magnification

What is biological magnification?

Biological magnification, or biomagnification, is the increasing buildup of toxic substances within organisms that happens at each stage of the food chain.

For example, when a lion eats a crocodile (yes, this happens), it ingests the toxins in the crocodile, which include the toxins from all the animals that the crocodile has ever eaten, which include the toxins from all the plants that those animals have ever eaten. At each stage of the food chain, the toxic buildup increases.

The buildup of toxic substances within a single organism is called biological accumulation. Biological magnification, then, is when the biological accumulation in each organism is compounded (added together, or magnified). Due to biomagnification, the amount of toxic substances (such as mercury or pesticides) is greater in the bodies of organisms (including humans) that consume other organisms.

Biological magnification occurs because some toxic substances don’t get broken down or filtered out of the body. This means that every organism that eats another gets loaded up with a lot of accumulated bad stuff.

Why is biological magnification important in biology?

Like it or not, there are toxins in many of the foods that we eat. A well-known toxic substance is mercury, which is found in high concentrations in certain fish. When you eat a fish, you are also consuming any mercury it may contain, and in large concentrations, mercury can have severe effects on the human body. Other toxic substances include the chemical bisphenol-A (BPA), which is found in some plastic containers and can leach into food, and polycyclic aromatic hydrocarbons (PAHs), which occur as a by-product of grilling meat.

To understand biological magnification, it is important to understand how the food chain works. In the food chain, there are producers and consumers. Producers create their own food and do not need to physically eat anything. Plants are the main producers because they use energy from the sun to create their own food (through photosynthesis). Consumers that eat producers (plants) are called herbivores; consumers that eat other consumers are called carnivores; and consumers that eat both are called omnivores. Through bioaccumulation, all organisms build up toxic substances over time. When any one of these organisms gets eaten, all of its toxins are eaten along with it, so this toxic buildup is magnified at each step in the food chain.

Since the introduction of pesticides and herbicides, there are more and more toxic substances that can biomagnify. The once commonly used insecticide DDT was banned for agricultural use in many countries in the 1970s, but it can still be found in the bodies of some animals today. It was especially harmful to bald eagles, who ate fish contaminated with the chemical, which had run off into bodies of water. The DDT caused the shells of eagles’ eggs to be thinner, leading to fewer hatchlings. Because of this, the bald eagle nearly became extinct, and since the DDT ban, it has taken decades for its population to recover.

Did you know ... ?

Mercury concentration is higher in some fish than others. Not surprisingly, bigger fish that eat a lot of other fish have the highest concentrations, including mackerel, tuna, grouper, sharks, and swordfish.

What are real-life examples of biological magnification?

Biological magnification is an important part of understanding how the food chain works. Because we can’t assume that a toxic substance will just go away, we need to be extra careful about what we eat and what kinds of things we put into the environment.

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What other words are related to biological magnification?

Quiz yourself!

True or false?

Biological magnification is the same as biological accumulation.

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