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8/3/2019 Pesticides Farming
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Pesticides andOrganic Farming
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Pesticides
• Herbicides
• Insecticides
• Fungicides
• Bactericides
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•Pests, DDT and biomagnification
•DDT, eagles and falcons•Endangered Species Act•Organic farming
Overview of Lesson
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Domestic crops wereselected for maximum
productivity and had littlenatural pest resistance
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Blight hitspotatoes, 1845
Based on: Population Reports , May 1992
Potato famine of Ireland was caused bygenetically uniform crops and lack of
pesticides to protect them
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Pests attack andeat our food crops
This problem isdue, in part, to notselecting for pestresistance duringdomestication
Today‟s Pests
Based on: National Geographic , February 1980
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DDT was invented in the1940‟s and viewed as: - miracle for farmers- and safe
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“The most discussed of the new insecticides is
dichloro-diphenyl-trichloroethane, shortened to
DDT but also called Guesarol. This compound hasremarkable power to kill insects, particularly bodylice-the „cooties‟ of World War I. The prevalence of
typhus, carried by body lice, in the Mediterranean
theater of this war has emphasized its value.DDT‟s effectiveness in war may well be
overshadowed by its value in peace. Painstakinginvestigations have shown it to be signally
effective against many of the most destructiveinsects that feed upon crops.”
Scientific American , July 1944.
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Arial crop sprayerswere used to spray
tons of DDT oncrops across theU.S.
Photo courtesy of Texas Parks and Wildlife Department
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Pests became resistant to DDT
Based on: National Geographic
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Pesticide Resistance
In the beginning, mostpests were sensitive toDDT but a few were
resistant
The resistant forms
survived and reproduced
In the end, most pestswere resistant to DDT
Based on: National Geographic , February 1980
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Biomagnification
The concentration ofpesticides in higher levels of
food chains
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Pesticides
Persistence+ Lipid solubility
= Bioacculmulation
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Bioaccumulation
waterzooplanktonsmallfishlri
E.g DDT
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Most food chains consist of four trophic levels
Based on: Mader, S., Inquiry Into Life , McGraw-Hill
Trophic Levels
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Energy Availableto Consumers at
Next Trophic Level
Energy Lost byRespiration
Energy Lost byDeath and Decay
Energy Lost byExcretion
Energy Lost by
Egestion of Feces
Energy Ingested
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DDT is concentrated asit moved up food chain
This is because energyis lost (from respiration)as you go up the foodchain but DDT is not
Based on: Campbell et al, Biology: Concepts
and Connections , Benjamin Cummings
DDT in Food Chain
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•Pests, DDT and biomagnification•DDT, eagles and falcons •Endangered Species Act•Organic foods
Overview of Lesson
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Bald Eagle
•
Once was widelydistributed over U.S.
•As a top carnivore itfeeds on fish
•Swoops down and
captures fish off thesurface of the water
Photo courtesy of Texas Parks and WildlifeDepartment
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•Scientists discovered that DDT wasconcentrated in the bald eagle
•DDT affected the eagle‟s ability to reproduce
Photos courtesy of Texas Parks and Wildlife Department
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Scientists foundthat the eagle eggshad thin egg shellsand broke easily
Nests containedbroken, rotten eggs
The number of
young producedper breedingpair was reduced
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Population of adulteagles declined to 4,000and the eagle was listedas “Endangered”
Photo courtesy of Texas Parks and Wildlife Department
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The Environmental Protection Agency (EPA)banned DDT in 1972
Photo courtesy of Texas Parks and Wildlife Department
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Eagle reproduction before and after DDT ban
Based on: Grier, J., Science, 1982
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Eagle populations increased rapidly andthe eagle is now listed as “Threatened”
From: Time , July 11, 1994
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Peregrine Falcon •Occurred naturallyover most of
continental U.S.
•Nests on cliffs
•Keen eyesight(if human, could readnewspaper print at 110 yards)
•Feeds on other birds,knocking them out ofthe sky at 200 m.p.h.
Photo courtesy of Texas Parks and Wildlife Department
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•After DDT was introducedin 1940s, DDT weakened
the birds‟ egg shells, devastating the population
•By early 1970s, the entire
U.S. population was downto 12 breeding pairs
•Peregrines were declaredfederally endangered and
DDT banned
•Peregrines were bred incaptivity and reintroduced
successfully in cities
DDT & Peregrine
Photos courtesy of Texas Parks and Wildlife Department
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•Pests, DDT and biomagnification•
DDT, eagles and falcons•Endangered Species Act•Organic foods
Overview of Lesson
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“In the United States at least 500 species and subspecies of plantsand animals have become extinct
since the 1500s.”
Douglas Chadwick, H., National Geographic , March 1995
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Endangered Species Act of 1973
• The Secretary of the Interiordetermines whether a species is
endangered or threatened
• The Secretary develops and
implements recovery plans for theconservation of endangered species
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Definitions - Endangered
Species Act • Endangered Species - Any species that is
in danger of extinction throughout all or a
significant portion of its range
• Threatened Species - Any species that is
likely to become an endangered specieswithin the foreseeable future
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OTHER COMEBACKSESA is having
somesuccess
2009 StatsAnimals 613Plants 747
endangeredspecies in the
U.S.
Gray whale(California population)
Aleutian Canadagoose
American alligator
Brown pelicanUtah prairie dot
Greenback cutthroattrout
1994
1985
1990
1987
1984
1978
date ofchange
Species removed from
endangered list orreclassified as threatened
Based on: Time , July 11, 1994
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•Pests, DDT and biomagnification•
DDT, eagles and falcons•Endangered Species Act•Organic foods
Overview of Lesson
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Defining “Organic”
Foods produced withouthormones, antibiotics,herbicides, insecticides,
chemical fertilizers,genetic modification orgerm-killing radiation
The USDA labels suchfoods “certified organic”
From: Newsweek , Sept. 30, 2002
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Availability of Organic Products
Based on: Newsweek , Sept. 30, 2002
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Unanswered Questions about
Certified Organic FoodsAre organic food safer than other foods?
Do organic foods taste better?
Are organic foods worth the extra costs?
Are people eating organic diets healthier thanpeople with conventional diets?
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Can organic farming help
the environment?
Pesticides now kill 67 million American
birds per year
The Mississippi River dumps enoughfertilizer into the Gulf of Mexico to maintain
a 60 mile “dead zone” devoid of fish
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Pesticides and Human Health
India suffering from human healthconsequences of pesticide use
•
Infertility•Cancer related deaths increasing•Childhood cancers•Mental retardation
Research shows pesticides and fertilizersin the groundwater.