Unit C Lesson 10: Hazardous Chemicals and Organisms
Completion requirements
Unit C Lesson 10: Hazardous Chemicals and Organisms |
Learning Targets |
Big Question: How can hazardous chemicals affect living organisms?
Plants and animals living on Earth have developed structures and behaviours for survival, but very few can survive sudden exposure to hazardous chemicals.
Plants and animals living on Earth have developed structures and behaviours for survival, but very few can survive sudden exposure to hazardous chemicals.
At the end of this inquiry, you should be able to answer the following questions:
- What is bioaccumulation?
- What is biomagnification?
Page 248 in your textbook will help you answer these questions about how hazardous chemicals can affect living things.
Introduction
Figure 1 – Bald Eagle
Figure 2 – Peregrine Falcon
Figure 3 – Thin egg shells often break before a bird is ready to hatch.
In the 1950s, there was dramatic decline in the
population
of bald eagles in the United States as well as peregrine falcons in Canada. In the 1960s, scientists discovered that the egg shells of many species of birds in North America were very thin and broke easily, which resulted in fewer chicks being hatched.
What could cause this?
Bioaccumulation occurs if a pollutant is picked by one individual organism and is not broken down or eliminated from its body. Instead, the pollutant collects in that organism's body fatty tissues. It is for this reason that fat-soluble pollutants are often much more dangerous to a food chain than water-soluble pollutants. Even if a water-soluble pollutant may be more toxic, the fact that it dissolves in water makes it much more likely to easily excreted (such as in urine, or sweat) by the consumers in the food chain. Fat-soluble pollutants are more difficult for consumers to remove because the pollutant is dissolved in the fat that is stored in their bodies.
Biomagnification is the increase in concentration of a pollutant as you move up a food chain. One eagle can eat one hundred fish, accumulating all of their toxins over time.
Prior to 1972, when its use was banned, DDT was a common pesticide.
The amount of a pollutant increases up the food chain. Initially, concentration of DDT in the water is 1 part. The producers have a DDT concentration of 1 000 parts. By the time that DDT reaches the bald eagle, its concentration was 10 million times the original concentration in water.
Scientists discovered that DDT affected the eggshells of the bald eagles, causing the eggshells to be thin. Most eggs broke and therefore did not hatch. This was the reason for the dramatic decline of the bald eagle populations as well as many other birds such as the peregrine falcon and Canada geese.
Bioaccumulation occurs if a pollutant is picked by one individual organism and is not broken down or eliminated from its body. Instead, the pollutant collects in that organism's body fatty tissues. It is for this reason that fat-soluble pollutants are often much more dangerous to a food chain than water-soluble pollutants. Even if a water-soluble pollutant may be more toxic, the fact that it dissolves in water makes it much more likely to easily excreted (such as in urine, or sweat) by the consumers in the food chain. Fat-soluble pollutants are more difficult for consumers to remove because the pollutant is dissolved in the fat that is stored in their bodies.
Biomagnification is the increase in concentration of a pollutant as you move up a food chain. One eagle can eat one hundred fish, accumulating all of their toxins over time.
Prior to 1972, when its use was banned, DDT was a common pesticide.
The amount of a pollutant increases up the food chain. Initially, concentration of DDT in the water is 1 part. The producers have a DDT concentration of 1 000 parts. By the time that DDT reaches the bald eagle, its concentration was 10 million times the original concentration in water.
Scientists discovered that DDT affected the eggshells of the bald eagles, causing the eggshells to be thin. Most eggs broke and therefore did not hatch. This was the reason for the dramatic decline of the bald eagle populations as well as many other birds such as the peregrine falcon and Canada geese.
Figure 4 – Bioaccumulation
Watch
Watch the following video carefully. It does an excellent job of explaining how the concentration of chemicals that we add to the environment can change, sometimes in ways we do not expect.
Try It!
Biomagnification
- DOWNLOAD this practice worksheet (S9_UC_S3_L10_biomagnification). If you prefer to use a Google Drive or PDF version of the worksheet, click here.
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The video below, "Biological Magnification", shows how DDT is incredibly dangerous to the animals in food chains. As you watch the video, answer the four questions on the worksheet.
- The video below, "Biomagnification!", reveals how poisons become more concentrated in food chains. As you watch that video, complete the table on the worksheet.
- The video below, "Mercury Pollution", provides useful perspective on the bioaccumulation of mercury, so be sure to watch that as well.
- When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
Mercury Pollution is a problem in water ecosystem. Watch the video "Mercury Pollution - An Invisible Foe that Knows No Boundaries" to find out more.
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The top predator has the highest concentration of DDT.
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DDT was hidden and stored in polar ice.
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DDT was weakening shells and fewer chicks were hatching.
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Rachel Carson brought attention to the overuse of DDT and how it was affecting the environment.
Watch
Just how harmful are chemical pollutants on organisms and humans? Figuring out how harmful a substance often involves determining the lethal dose of a chemical. Watch the following video carefully for an overview of how chemical pollutants affect organisms,
and also for a explanation of lethal dose.