This document discusses biological magnification through the example of DDT. It describes how DDT was widely used as an inexpensive insecticide in the mid-20th century but was later found to biomagnify up the food chain and cause eggshell thinning in birds. The document outlines the 10% rule of energy transfer between trophic levels and explains how DDT accumulation increased from primary consumers to secondary consumers. Rachel Carson's book Silent Spring brought attention to the environmental impacts of DDT and other pesticides.

1. Biological Magnification

2. 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.

3. Food chain or food web?

4. “10% Rule”

5. 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.

6. 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).

7. 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.

8. • 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.

9. • 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.

10. Ecological Pyramid
• Parts per million
• Explains how the
accumulation
increases
because
Secondary
Consumers eat
more than one
Primary
Consumer

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

12. Crushed egg shell next to normal egg shell
• DDT affected eggs
are crushed when sat
on by the mother bird

13. How does this affect us?

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

15. 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.

16. The Biomagnification Game
• Grasshoppers
• Shrews
• Hawks
• Two difference “food sources” (hence, two
different colored Hershey’s Kisses)