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.
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
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)
