Review & Discussion

Agricultural Systems and Transgenic Organisms

Question: Many of us take agriculture for granted. How has it affected human history?Photos courtesy of Texas Parks and Wildlife Department

Development of agricultural systems made advanced civilization possible

10,000 BC

Photo courtesy of Texas Department of Transportation

Today

Question: When did domestication begin and what was the first animal domesticated?

Dates (BC) and Places of First Evidence for Domestication

from Diamond, J., Guns, Germs and Steel, Random House, 1997

Dog 10,000 BC SW. Asia,China, North AmericaSheep8,000 BC SW. AsiaGoat 8,000 BC SW. AsiaPig 8,000 BC China, SW. AsiaCow 6,000 BC SW. Asia, India, North AfricaHorse 4,000 BC UkraineDonkey 4,000 BC Egypt

From: Fort Worth Star-Telegram

•The dog was one of the first animals domesticated

•10,000 years of domestication may explain why dogs are man’s best friend

Question: Why is there a controversy over using grain to fatten cattle?

From: Time, November 8, 1999

Many more people could be fed by the grain used to feed the cattle than can be fed by the cattle themselves

This is because productive energy is diminished with each trophic level

Based on: Scientific American, September 1976

Question: What is good and bad about genetically engineered agricultural plants?

Genetically Engineered Plants• The Good: Crops can be engineered to

have important components of diet, contain medically important proteins, and to be pest resistant

• The Bad: Plants could contain pesticides that would harm humans and wildlife, or proteins that could cause allergies in humans. Genetics could escape to traditional crops.

Today’s LessonToday’s Lesson

Pesticides and Pesticides and Organic FarmingOrganic Farming

•Pests, DDT and biomagnification•DDT, eagles and falcons•Endangered Species Act•Organic farming

Overview of Lesson

Domestic crops were Domestic crops were selected for maximum selected for maximum

productivity and had little productivity and had little natural pest resistancenatural pest resistance

Blight hits potatoes, 1845

Based on: Population Reports, May 1992

Potato famine of Ireland was caused by genetically uniform crops and lack of

pesticides to protect them

Pests attack and Pests attack and eat our food cropseat our food crops

This problem is This problem is due, in part, to not due, in part, to not selecting for pest selecting for pest resistance during resistance during domesticationdomestication

Today’s PestsToday’s Pests

Based on: National Geographic, February 1980

DDT was invented in the DDT was invented in the 1940’s and viewed as:1940’s and viewed as:- miracle for farmers- miracle for farmers- and safe- and safe

““The most discussed of the new insecticides is The most discussed of the new insecticides is dichloro-diphenyl-trichloroethane, shortened to dichloro-diphenyl-trichloroethane, shortened to DDT but also called Guesarol. This compound has DDT but also called Guesarol. This compound has remarkable power to kill insects, particularly body remarkable power to kill insects, particularly body lice-the ‘cooties’ of World War I. The prevalence of lice-the ‘cooties’ of World War I. The prevalence of typhus, carried by body lice, in the Mediterranean typhus, carried by body lice, in the Mediterranean theater of this war has emphasized its value. theater of this war has emphasized its value. DDT’s effectiveness in war may well be DDT’s effectiveness in war may well be overshadowed by its value in peace. Painstaking overshadowed by its value in peace. Painstaking investigations have shown it to be signally investigations have shown it to be signally effective against many of the most destructive effective against many of the most destructive insects that feed upon crops.”insects that feed upon crops.”

Scientific AmericanScientific American, July 1944., July 1944.

Arial crop sprayers Arial crop sprayers were used to spray were used to spray tons of DDT on tons of DDT on crops across the crops across the U.S.U.S.

Photo courtesy of Texas Parks and Wildlife DepartmentPhoto courtesy of Texas Parks and Wildlife Department

Pests became resistant to DDTPests became resistant to DDT

Based on: National Geographic

Pesticide ResistancePesticide Resistance

In the beginning, most In the beginning, most pests were sensitive to pests were sensitive to DDT but a few were DDT but a few were resistantresistant

The resistant forms The resistant forms survived and reproducedsurvived and reproduced

In the end, most pests In the end, most pests were resistant to DDTwere resistant to DDT

Based on: National Geographic, February 1980

BiomagnificationBiomagnification

The concentration of The concentration of pesticides in higher levels of pesticides in higher levels of

food chainsfood chains

Most food chains consist of four trophic levels

Based on: Mader, S., Inquiry Into Life, McGraw-Hill

Trophic Levels

Energy Available to Consumers at

Next Trophic Level

Energy Lost by Respiration

Energy Lost by Death and Decay

Energy Lost by Excretion

Energy Lost by Egestion of Feces

Energy Ingested

DDT is concentrated as DDT is concentrated as it moved up food chainit moved up food chain

This is because energy This is because energy is lost (from respiration) is lost (from respiration) as go up food chain but as go up food chain but DDT is notDDT is not

Based on: Campbell et al, Biology: Concepts and Connections, Benjamin Cummings

DDT in Food Chain

•Pests, DDT and biomagnification•DDT, eagles and falcons•Endangered Species Act•Organic foods

Overview of Lesson

Bald EagleBald Eagle

•Once was widelyOnce was widely distributed over U.S.distributed over U.S.

•As a top carnivore it As a top carnivore it feeds on fishfeeds on fish

•Swoops down and Swoops down and captures fish off the captures fish off the surface of the watersurface of the water

Photo courtesy of Texas Parks and Wildlife Photo courtesy of Texas Parks and Wildlife DepartmentDepartment

•Scientists discovered that DDT wasScientists discovered that DDT was concentrated in the bald eagle concentrated in the bald eagle

•DDT affected the eagle’s ability to reproduceDDT affected the eagle’s ability to reproduce

Photos courtesy of Texas Parks and Wildlife DepartmentPhotos courtesy of Texas Parks and Wildlife Department

Scientists found Scientists found that the eagle eggs that the eagle eggs had thin egg shells had thin egg shells and broke easilyand broke easily

Nests contained Nests contained broken, rotten eggsbroken, rotten eggs

The number of The number of young produced per young produced per breedingbreedingpair was reducedpair was reduced

Population of adult Population of adult eagles declined to 4,000 eagles declined to 4,000 and the eagle was listed and the eagle was listed as “Endangered”as “Endangered”

Photo courtesy of Texas Parks and Wildlife DepartmentPhoto courtesy of Texas Parks and Wildlife Department

The Environmental Protection Agency (EPA) The Environmental Protection Agency (EPA) banned DDT in 1972banned DDT in 1972

Photo courtesy of Texas Parks and Wildlife DepartmentPhoto courtesy of Texas Parks and Wildlife Department

Eagle reproduction before and after DDT ban Eagle reproduction before and after DDT ban

Based on: Grier, J., Science, 1982

Eagle populations increased rapidly and Eagle populations increased rapidly and the eagle is now listed as “Threatened”the eagle is now listed as “Threatened”

From: Time, July 11, 1994

Peregrine FalconPeregrine Falcon •Occurred naturallyOccurred naturally over most of over most of continental U.S.continental U.S.

•Nests on cliffsNests on cliffs

•Keen eyesight Keen eyesight (if human, could read (if human, could read newspaper print at 110 yards)newspaper print at 110 yards)

•Feeds on other birds, Feeds on other birds, knocking them out of knocking them out of the sky at 200 m.p.h.the sky at 200 m.p.h.

Photo courtesy of Texas Parks and Wildlife DepartmentPhoto courtesy of Texas Parks and Wildlife Department

•After DDT was introducedAfter DDT was introduced in 1940s, DDT weakenedin 1940s, DDT weakened the birds’ egg shells,the birds’ egg shells, devastating the populationdevastating the population

•By early 1970s, the entireBy early 1970s, the entire U.S. population was downU.S. population was down to 12 breeding pairsto 12 breeding pairs

•Peregrines were declaredPeregrines were declared federally endangered andfederally endangered and DDT bannedDDT banned

•Peregrines were bred inPeregrines were bred in captivity and reintroducedcaptivity and reintroduced successfully in citiessuccessfully in cities

DDT & PeregrineDDT & Peregrine

Photos courtesy of Texas Parks and Wildlife DepartmentPhotos courtesy of Texas Parks and Wildlife Department

•Pests, DDT and biomagnification•DDT, eagles and falcons•Endangered Species Act•Organic foods

Overview of Lesson

““In the United States at least 500In the United States at least 500species and subspecies of plantsspecies and subspecies of plantsand animals have become extinctand animals have become extinctsince the 1500s.”since the 1500s.”

Douglas Chadwick, H., Douglas Chadwick, H., National GeographicNational Geographic, March 1995, March 1995

Endangered Species Act of 1973Endangered Species Act of 1973

• The Secretary of the Interior The Secretary of the Interior determines whether a species is determines whether a species is endangered or threatened endangered or threatened

• The Secretary develops and The Secretary develops and implements recovery plans for the implements recovery plans for the conservation of endangered speciesconservation of endangered species

Definitions - Endangered Definitions - Endangered Species ActSpecies Act

• Endangered SpeciesEndangered Species - Any species that is - Any species that is in danger of extinction throughout all or a in danger of extinction throughout all or a significant portion of its rangesignificant portion of its range

• Threatened SpeciesThreatened Species - Any species that is - Any species that is likely to become an endangered species likely to become an endangered species within the foreseeable futurewithin the foreseeable future

OTHER COMEBACKS ESA is having

some success

2009 StatsAnimals 613Plants 747

endangered species in the U.S.

Gray whale (California population)

Aleutian Canada goose

American alligator

Brown pelican

Utah prairie dot

Greenback cutthroat trout

1994

1985

1990

1987

1984

1978

date of change

Species removed from endangered list or reclassified as threatened

Based on: Time, July 11, 1994

•Pests, DDT and biomagnification•DDT, eagles and falcons•Endangered Species Act•Organic foods

Overview of Lesson

Defining “Organic”Defining “Organic”

Foods produced without Foods produced without hormones, antibiotics, hormones, antibiotics, herbicides, insecticides, herbicides, insecticides, chemical fertilizers, chemical fertilizers, genetic modification or genetic modification or germ-killing radiationgerm-killing radiation

The USDA labels such The USDA labels such foods “certified organic”foods “certified organic”

From: From: NewsweekNewsweek, Sept. 30, 2002, Sept. 30, 2002

Availability of Organic Products

Based on: Based on: NewsweekNewsweek, Sept. 30, 2002, Sept. 30, 2002

Unanswered Questions about Unanswered Questions about Certified Organic FoodsCertified Organic Foods

Are organic food safer than other foods?Are organic food safer than other foods?

Do organic foods taste better?Do organic foods taste better?

Are organic foods worth the extra costs?Are organic foods worth the extra costs?

Are people eating organic diets healthier than Are people eating organic diets healthier than people with conventional diets?people with conventional diets?

Can organic farming help Can organic farming help the environment?the environment?

Pesticides now kill 67 million American Pesticides now kill 67 million American birds per yearbirds per year

The Mississippi River dumps enough The Mississippi River dumps enough fertilizer into the Gulf of Mexico to maintain fertilizer into the Gulf of Mexico to maintain a 60 mile “dead zone” devoid of fisha 60 mile “dead zone” devoid of fish

Pesticides and Human HealthPesticides and Human Health

India suffering from human health India suffering from human health consequences of pesticide useconsequences of pesticide use

•InfertilityInfertility•Cancer related deaths increasingCancer related deaths increasing•Childhood cancersChildhood cancers•Mental retardationMental retardation

Research shows pesticides and fertilizers Research shows pesticides and fertilizers in the groundwater.in the groundwater.