Back To CourseHuman Physiology Study Guide
12 chapters | 151 lessons
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Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.
Let's say you are a bird of prey, a soaring hawk whose favorite meal is snakes. Snakes are so tasty! They're also fun to catch and you're quite good at it. You don't think much about snakes other than this, but you should. What that snake has eaten, and what its food has eaten, affects you in important ways. Biomagnification, which is the increase in concentration of toxins up the food chain, especially affects you.
Chemicals and toxins accumulate more and more as you move up the food chain, because they do not get broken down in the body. So you may think you are a hawk that just likes to eat snakes, but when you eat a snake, you also eat all of the mice, frogs, and other things that snakes find tasty. And while the small mice and frogs may only have small amounts of chemicals or toxins in their systems, a snake might eat 10 mice and 20 frogs before you get to it. Meaning, you absorb the chemicals and toxins of 10 mice, 20 frogs, and a snake into your own tissues.
What exactly are these things you're taking into your body? They come in a variety of shapes and sizes. They could be things like mercury, lead, and other heavy metals. Other environmental-related chemicals include Polychlorinated Biphenyls (PCBs), found in things like motor oil, plastics, and even tape; Polycyclic Aromatic Hydrocarbons (PAHs), from burning carbon-containing compounds such as wood and gasoline; and even pharmaceuticals, such as ibuprofen and birth control that go through people's bodies and end up in waste water.
As you can see, things that can biomagnify cut a wide swath. Anything that gets into biological tissue, that isn't normally there, has the potential to accumulate and magnify as it moves up the food chain. Some things are more harmful than others, but it's still important to take note that they can become problematic the further up they go.
We haven't always been acutely aware of biomagnification. It took a few severe situations for people to realize the effect our products have on wildlife and sometimes ourselves. Here are a few examples.
One of the most famous cases of biomagnification is the one involving DDT, which is a pesticide that was historically used for mosquito control, as well as on agricultural crops, and bird eggs. DDT was widely used starting in the mid-40s, but was banned in the United States in 1972 because of its harmful effects on wildlife.
When birds take up DDT into their bodies, it becomes difficult for them to absorb calcium, necessary to produce strong eggshells. Birds that have accumulated DDT in their bodies produce eggs with very thin shells, which can often break before they hatch. As a bird of prey, you may only lay a few eggs at a time. And if you lay only three eggs and two of them break, then your population shrinks pretty quickly. This is exactly what happened to the birds of prey during the widespread use of DDT.
Mercury, a liquid element on the periodic table that is highly toxic, is one of those toxins that gets a lot of attention because it can eventually make its way into human tissue. The most prominent way this occurs is through fish and other seafood. Mercury exists in ocean sediments and in the water, and may be taken up by plants and plankton. Small marine animals come along and eat these plants and plankton, and then bigger marine animals eat those animals, and so on.
Fish can also absorb mercury through their gills as well as through their food. Mercury holds very fast to fish tissue, though the amount of mercury varies by fish species as well as location. Women who want to get pregnant, and those who are already pregnant, are advised not to eat seafood because mercury can cause developmental defects in the baby.
A growing concern in marine science these days is microplastics, which are plastic pieces less than five millimeter in length. They come from a variety of sources such as larger plastics that degrade and break down, as well as microbeads, tiny little beads found in cosmetics and personal care products.
We're just starting to learn about the potential harm that microplastics may have, but we do know that some fish eat these small pieces of plastic because they think they are small pieces of food. The chemicals in those plastics get into the fish tissue. Guess what happens next? The chemicals accumulate and work their way up the food chain. So if you are a top predator (humans included) that eats a fish that ate a bunch of little fish that ate a bunch of microplastic pieces, watch out! Those chemicals are now in your body as well.
Being at the top of the food chain definitely has its perks! Unfortunately, biomagnification is not one of them, since this is the increase in concentration of toxins up the food chain. Biomagnification occurs because certain chemicals and toxins do not break down in the body, and instead are passed to the consumer.
There are many, many different chemicals and substances that can be problematic. Some of the major players include heavy metals, like mercury, which easily binds to fish tissue and poses a threat to human health. Other examples are PCBs, found in motor oils and plastics; PAHs, from burning carbon-containing compounds; pharmaceuticals that pass through people's bodies; and even pesticides such as the historically used DDT, which is a pesticide that was historically used for mosquito control, as well as on agricultural crops; and mercury, which is a liquid element on the periodic table that is highly toxic, which can cause birth defects in pregnant women who consume contaminated fish.
Microplastics are a fairly new concern for biomagnification. These are pieces of plastic that are less than five millimeters in length, and because of their size, they often look like food to the fish and other marine life. We don't know yet just how dangerous microplastics may be to our health, but because the compounds are not ones broken down in the body, they are something to carefully watch.
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Back To CourseHuman Physiology Study Guide
12 chapters | 151 lessons
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