Biological Magnification

After successfully participating in this lab, you will be able to:

• Describe the reasons DDT was used in America.

• Identify the biological impact of DDT.

• Explain biomagnification.

• Compare herbicides, insecticides, pesticides, and organic products.

• Contrast food chains and food webs.

Food chain or food web?

“10% Rule”

10% Rule

• https://www.youtube.com/watch?v=ScizkxMlEOM

• This rule specifically refers to energy transfer in a food chain. According to the rule, only 10% of energy is transferred to the next level of food chain, out of the remaining 90%, some is used up metabolically for survival and the rest is lost as body heat.

What is DDT?

• Chlorinated hydrocarbon

• Considered highly toxic to insects, but didn’t (immediately) kill mammals or humans.

• Popular because it killed mosquitoes (who spread malaria) and cockroaches (which are human pests).

Background Information

• DDT was discovered in the 1930’s by Paul Muller, a Swiss chemist

• It was inexpensive, broad-spectrum, persistent chemical that was extremely toxic to insects but not to humans and other mammals

• It was used to control lice, mosquitoes, spruce budworm and beetles, and to help grow more economically productive crops.

• In the 1950’s Rachel Carson investigated the effects of DDT on wildlife. Her book, Silent Spring, chronicles a message that insecticides can have dangerous environmental effects.

• Rachel Carson has been credited with the creation of the Environmental Protection Agency (EPA).

• The EPA worked to ban DDT in the early 1970’s• DDT is still believed to be entering the Great

Lakes ecosystem through rainfall and dust sources from halfway around the world, to this day.

• The study of DDT provides a good example of biological magnification or “biomagnification” of the chemicals in the ecosystem

• Biomagnification is the accumulation of higher and higher concentrations of chemicals in individual organisms.

• It occurs when a chemical is ingested and cannot be broken down or excreted, leading to accumulation of chemical that they pass along a food chain.

Ecological Pyramid

• Parts per million• Explains how the

accumulation increases because Secondary Consumers eat more than one Primary Consumer

http://www.youtube.com/watch?v=E5P-UoKLx1A

Crushed egg shell next to normal egg shell

• DDT affected eggs are crushed when sat on by the mother bird

How does this affect us?

http://www.youtube.com/watch?v=LQ64sV0nSVU&feature=related

The Present

• Many new pesticides are biologically based and breakdown readily upon contact with soil or in reaction to sunlight

• Much more target-specific and less likely to damage on-target organisms.

• Persistence of a chemical is tested during the pesticide registration process by the Pest Management Regulatory Agency.

• Long term effects and overall impact of new and existing chemicals on ecosystems can only be partially evaluated by current laboratory testing procedures.

The Biomagnification Game

• Grasshoppers

• Shrews

• Hawks

• Two difference “food sources” (hence, two different colored Hershey’s Kisses)