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Science 9

Science 9. Lesson 9.3.3. A Growing Concern Textbook Reference Science Focus 9 pages 187 to 196. Chemical Use. An area of rapid change since the Second World War has been in the field of applied ________.

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Science 9

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  1. Science 9 Lesson 9.3.3. A Growing Concern Textbook Reference Science Focus 9 pages 187 to 196

  2. Chemical Use • An area of rapid change since the Second World War has been in the field of applied ________. • The research laboratories of __________ companies have created a steady stream of new products. • __________ has been a major market for the chemical industry. • _________ and __________, along with chemical fertilizers, are used in large quantities on modern farms and in many homes.

  3. Chemical Use • Selective weed killers (_______________), such as 2-4-D, have revolutionized farming by controlling weeds. • Chemical _____________, such as D.D.T., have been used around the world to control the populations of insects that spread disease or that __________ with humans by eating our food crops.

  4. Chemical Use • Many chemicals produced and used by humans are toxic. Toxic chemicals are __________. D.D.T. was used in North America until 1969. It was banned on this continent because of the effects it had on ________ and other animals. • Even mildly __________ chemicals have to be used with care because they can be extremely hazardous if used incorrectly. • All pesticides have the disadvantage of killing more than their intended __________.

  5. Use this model of a food web to answer the following questions.

  6. Trophic Levels • The mountain lion in this model of a food chain is in the second __________ level when it eats a rabbit. • The mountain lion is a _________ order consumer. Remember that the mountain lion is also called a ____________.

  7. Food Chains • 1. Can you identify three other herbivores (first order consumers)? • 2. Which organisms on this diagram are decomposers?

  8. Food Chains • 3. Which animal would the mountain lion have to eat in order to be a 3rd order consumer? • 4. Which scientific model is represented by the sequence: grass -> grasshopper -> shrews -> fox -> mountain?

  9. Pest Resistance • Scientists recognize that the wide spread use of ______________ has lead to the development of pesticide-resistant insects. • These insects have developed a resistance to the pesticides that we are currently using and their __________ are increasing.

  10. Graph showing what happens to the population of mosquitoes before, during, and after spraying with a chemical pesticide.

  11. Pest Resistance • 1. What was the original population of mosquitoes before the spraying program started? • 2. Describe what happened to the population of mosquitoes between 30 days and 60 days. What do you think was the cause of this decline?

  12. Pest Resistance • 3. Describe what happened to the population of mosquitoes between 30 days and 90 days. • 4. Why do you think the insect population increased even though humans were still using chemical sprays to kill the mosquitoes?

  13. Biological Magnification • As materials pass through an ecosystem they may become ______________ in the tissues of living creatures. • This phenomenon is known as biological magnification or ________________.

  14. This is a model of a salt-water food web. Pesticides accumulate in the fatty tissue of top predators such as killer whales and dolphins. This process is called biological magnification.

  15. Biological Magnification • Organisms at the bottom of the food chain, such as microscopic algae, may absorb minute quantities of ________ chemicals such as D.D.T. Many such chemicals are ________ soluble and are not excreted easily. Therefore they become more concentrated toward the top of the _____ ______. • In the top ____________, the chemicals may be concentrated enough to have damaging effects.

  16. Science 9.3.3. Assignment • Read the Think & Link Investigation 3–B DDT in a Food Chain on pages 189 to190. • Do the following questions: • (a) Analyze questions 1 to 6 on page 191. • (b) Conclude and Apply questions 7 and 8 on page 191 • (c) Extend Your Knowledge and Skills question 9 on page 191.

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