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This lesson will increase your knowledge of concepts covered in the following TEKS for biology: 3.a – Analyze, review, and critique scientific explanations,

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Presentation on theme: "This lesson will increase your knowledge of concepts covered in the following TEKS for biology: 3.a – Analyze, review, and critique scientific explanations,"— Presentation transcript:

1 This lesson will increase your knowledge of concepts covered in the following TEKS for biology: 3.a – Analyze, review, and critique scientific explanations, including hypotheses and theories, as to their strengths and weaknesses using scientific evidence and information 3.c – Evaluate impact of research on scientific thought, society, and the environment 3.f – Research and describe the history of biology and contributions of scientists 4.b – Investigate and identify cellular processes 6.d – Compare genetic variations observed in plants and animals 7.b – Illustrate the results of natural selection in the speciation, diversity, phylogeny, adaptation, behavior and extinction

2 This lesson will increase your knowledge of concepts covered in the following TEKS for biology: 9.d – Analyze the flow of matter and energy through different trophic levels and between organisms and the physical environment 11.b – Investigate and identify how organisms respond to external stimulation 11.c – Analyze the importance of nutrition, environmental conditions and physical exercise on health 11.d – Summarize the role of microorganisms in maintaining and disrupting equilibrium including diseases in plants and animals and decay in an ecosystem 12.b – Interpret interactions among organisms exhibiting predation, parasitism, commensalism, and mutualism 12.e – Investigate and explain interactions in an ecosystem including food chains, food webs, and food pyramids

3 Previous Lesson Agricultural Systems and Transgenic Organisms

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

5 Development of agricultural systems made advanced civilization possible 10,000 BC Photo courtesy of Texas Department of Transportation Today

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

7 Dates (BC) and Places of First Evidence for Domestication from Diamond, J., Guns, Germs and Steel, Random House, 1997 Dog10,000 BCSW. Asia,China, North America Sheep8,000 BCSW. Asia Goat8,000BCSW. Asia Pig8,000BCChina, SW. Asia Cow6,000BCSW. Asia, India, North Africa Horse4,000BCUkraine Donkey4,000BCEgypt

8 From: Fort Worth Star-Telegram The dog was one of the first animals domesticated 10,000 years of domestication may explain why dogs are mans best friend

9 Question: Why is there a controversy over using grain to fatten cattle? From: Time, November 8, 1999

10 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

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

12 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.

13 Todays Lesson Pesticides and Organic Farming

14 Pests, DDT and biomagnification DDT, eagles and falcons Endangered Species Act Organic farming Overview of Lesson

15 Domestic crops were selected for maximum productivity and had little natural pest resistance

16 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

17 Pests attack and eat our food crops This problem is due, in part, to not selecting for pest resistance during domestication Todays Pests Based on: National Geographic, February 1980

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

19 The most discussed of the new insecticides is dichloro-diphenyl-trichloroethane, shortened to DDT but also called Guesarol. This compound has remarkable power to kill insects, particularly body lice-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. DDTs effectiveness in war may well be overshadowed by its value in peace. Painstaking investigations have shown it to be signally effective against many of the most destructive insects that feed upon crops. Scientific American, July 1944.

20 Arial crop sprayers were used to spray tons of DDT on crops across the U.S. Photo courtesy of Texas Parks and Wildlife Department

21 Pests became resistant to DDT Based on: National Geographic

22 Pesticide Resistance In the beginning, most pests were sensitive to DDT but a few were resistant The resistant forms survived and reproduced In the end, most pests were resistant to DDT Based on: National Geographic, February 1980

23 Biomagnification The concentration of pesticides in higher levels of food chains

24 Most food chains consist of four trophic levels Based on: Mader, S., Inquiry Into Life, McGraw-Hill Trophic Levels

25 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

26 DDT is concentrated as it moved up food chain This is because energy is lost (from respiration) as go up food chain but DDT is not Based on: Campbell et al, Biology: Concepts and Connections, Benjamin Cummings DDT in Food Chain

27 Pests, DDT and biomagnification DDT, eagles and falcons Endangered Species Act Organic foods Overview of Lesson

28 Bald Eagle Once was widelyOnce was widely distributed over U.S. distributed over U.S. As a top carnivore it feeds on fishAs a top carnivore it feeds on fish Swoops down and captures fish off the surface of the waterSwoops down and captures fish off the surface of the water Photo courtesy of Texas Parks and Wildlife Department

29 Scientists discovered that DDT wasScientists discovered that DDT was concentrated in the bald eagle concentrated in the bald eagle DDT affected the eagles ability to reproduceDDT affected the eagles ability to reproduce Photos courtesy of Texas Parks and Wildlife Department

30 Scientists found that the eagle eggs had thin egg shells and broke easily Nests contained broken, rotten eggs The number of young produced per breeding pair was reduced

31 Population of adult eagles declined to 4,000 and the eagle was listed as Endangered Photo courtesy of Texas Parks and Wildlife Department

32 The Environmental Protection Agency (EPA) banned DDT in 1972 Photo courtesy of Texas Parks and Wildlife Department

33 Eagle reproduction before and after DDT ban Based on: Grier, J., Science, 1982

34 Eagle populations increased rapidly and the eagle is now listed as Threatened From: Time, July 11, 1994

35 Peregrine Falcon Occurred naturallyOccurred naturally over most of continental U.S. over most of continental U.S. Nests on cliffsNests on cliffs Keen eyesightKeen eyesight (if human, could read newspaper print at 110 yards) Feeds on other birds, knocking them out of the sky at 200 m.p.h.Feeds on other birds, knocking them out of the sky at 200 m.p.h. Photo courtesy of Texas Parks and Wildlife Department

36 After DDT was introducedAfter DDT was introduced in 1940s, DDT weakened in 1940s, DDT weakened the birds egg shells, the birds egg shells, devastating the population devastating the population By early 1970s, the entireBy early 1970s, the entire U.S. population was down U.S. population was down to 12 breeding pairs to 12 breeding pairs Peregrines were declaredPeregrines were declared federally endangered and federally endangered and DDT banned DDT banned Peregrines were bred inPeregrines were bred in captivity and reintroduced captivity and reintroduced successfully in cities successfully in cities DDT & Peregrine Photos courtesy of Texas Parks and Wildlife Department

37 Pests, DDT and biomagnification DDT, eagles and falcons Endangered Species Act Organic foods Overview of Lesson

38 In the United States at least 500 species and subspecies of plants and animals have become extinct since the 1500s. Douglas Chadwick, H., National Geographic, March 1995

39 Endangered Species Act of 1973 The Secretary of the Interior determines whether a species is endangered or threatenedThe Secretary of the Interior determines whether a species is endangered or threatened The Secretary develops and implements recovery plans for the conservation of endangered speciesThe Secretary develops and implements recovery plans for the conservation of endangered species

40 Definitions - Endangered Species Act Endangered Species - Any species that is in danger of extinction throughout all or a significant portion of its rangeEndangered 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 species within the foreseeable future Threatened Species - Any species that is likely to become an endangered species within the foreseeable future

41 OTHER COMEBACKS ESA is having some success 2009 Stats Animals 613 Plants 747 endangered species in the U.S. Gray whale (California population) Aleutian Canada goose American alligator Brown pelican Utah prairie dot Greenback cutthroat trout date of change Species removed from endangered list or reclassified as threatened Based on: Time, July 11, 1994

42 Pests, DDT and biomagnification DDT, eagles and falcons Endangered Species Act Organic foods Overview of Lesson

43 Defining Organic Foods produced without hormones, antibiotics, herbicides, insecticides, chemical fertilizers, genetic modification or germ-killing radiation The USDA labels such foods certified organic From: Newsweek, Sept. 30, 2002

44 Availability of Organic Products Based on: Newsweek, Sept. 30, 2002

45 Unanswered Questions about Certified Organic Foods Are organic food safer than other foods? Do organic foods taste better? Are organic foods worth the extra costs? Are people eating organic diets healthier than people with conventional diets?

46 Can organic farming help the environment? Pesticides now kill 67 million American birds per year The Mississippi River dumps enough fertilizer into the Gulf of Mexico to maintain a 60 mile dead zone devoid of fish

47 Pesticides and Human Health India suffering from human health consequences of pesticide use InfertilityInfertility Cancer related deaths increasingCancer related deaths increasing Childhood cancersChildhood cancers Mental retardationMental retardation Research shows pesticides and fertilizers in the groundwater.

48 Next Lesson The Water Cycle


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