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Chapter 2
Using Science to Address Environmental Problems
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Super Topic 1: The Scientific Method
*Never PROVES anything, only removes INCORRECT POSSIBILITIES
1. Recognize Question2. Research what is already known3. Develop a hypothesis to explain problem4. Design & Perform a testable experiment5. Analyze & Interpret data6. Reach conclusions & report own data
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Super Topic 2: Experimental Controls
1. Variable: a FACTOR that influences a processa. Independent: WHAT YOU’RE TESTING EFFECTS OF
b. Dependent: WHAT IS BEING MEASURED (the results)
c. Controls: WHAT REMAINS CONSTANT
2. Groups: a. Control: variable that is NOT ALTEREDb. Experimental: Independent variable is ALTERED IN A
KNOWN WAY
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Super Topic 3: Types of Reasoning
1. Inductive Reasoning: SPECIFIC TO GENERALa. Asks, “What does the grouped information have in
common?”b. Can produce NEW KNOWLEDGE, but is prone to
ERRORc. Ex. “Gold is a metal that is heavier than water
Iron is a metal that is heavier than water Silver is a metal that is heavier than water.”
Conclusion: All metals are heavier than water.
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Super Topic 3: Types of Reasoning (cont.)
2. Deductive Reasoning: GENERAL TO SPECIFICa. Adds NO NEW knowledge, but makes relationships
more APPARENT
b. Helps determine the type of EXPERIMENT or OBSERVATION necessary to test a hypothesis
c. Example: General Rule: All birds have wings Specific Example: Robins are birds Deduction: All robins have wings.
3. Theories: Integrated explanations of NUMEROUS HYPOTHESES*There is no ABSOLUTE TRUTH in science, only varying degrees of UNCERTAINTY!
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Deductive Reasoning v. Inductive Reasoning
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Super Topic 4: Risk & Risk Management
• Risk: PROBABILITY OF HARM• Risk Assessment: using STATISTICAL METHODS to
quantify the risk involved in a particular action so they can be COMPARED & CONTRASTED w/other risks.
• Risk Management: Determines whether a particular risk should be REDUCED or ELIMINATED, and if so, what should be done.– Considers the risk in terms of relevant POLITICAL,
SOCIAL, & ECONOMIC considerations
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Super Topic 4: Risk Management (Cont.)
• Varying Views:A. If we have control, it’s no big deal even though the
risk is high (ie, a diet)B. If we don’t have control, it’s a huge deal (pesticide
residue) even though the risk is low (ie, DDT is a cheap pesticide)
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Super Topic 4: Risk Assessment (cont.)
Four Steps of Risk Assessment:1. HAZARD IDENTIFICATION: does exposure cause an
increased likelihood of adverse health effect?2. DOSE-RESPONSE ASSESSMENT: the relationship b/w
amount of exposure and the seriousness of the health effect
3. EXPOSURE ASSESSMENT: how much, how often, how long is the exposure?
4. RISK CHARACTERIZATION: what is the probability of an individual population having an adverse health effect?
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The Steps of Risk Assessment
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Super Topic 5: Determining the Health Effects of Environmental Pollutants
• TOXICANTS: chemicals w/adverse health effects
• TOXICOLOGY: the study of toxicants• Two types of effects of toxicants on living
organisms:1. ACUTE: Immediately or closely following
exposure (ie, dizziness & and nausea)2. CHRONIC: Long-term effects such as damage to
vital organs (ie, kidney & lung damage)
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Super Topic 5 (cont.)
Dose and Response:1. Lethal Dose- 50%- (LD50): CAUSES DEATH IN 50% OF
TEST POPULATIONa. LD50 and toxicity are INVERSELY related:
As LD50 , toxicity (and vice versa)
2. Sub-Lethal Dose: causes harm, not death3. Threshold: maximum dose w/no measurable effect
a. Any dose less than threshold is safe4. Effective Dose- 50% (LD50): causes a specific reaction
within the BULK OF THE POPULATION
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Super Topic 5 (cont.)
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Super Topic 6: Cancer-Causing Substances & Risk Assessment of Chemical Mixtures
• CARCINOGEN: cancer causing substance • How to determine if chemicals are the cause– EPIDEMIOLOGICAL evidence of carcinogen
exposure– ANIMAL TESTING: very controversial and not
effective (animals react differently than humans)• Risk Assessment of Chemical Mixtures:
toxicology studies are usually performed on ONE CHEMICAL, not mixtures
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Super Topic 6 (cont.)
• Chemicals can interact in 3 ways:1. Additive: CHEMICALS ADD UP(1+1=2)2. Synergistic: GREATER COMBINED EFFECT (1+1=3)3. Antagonistic: SMALLER COMBINED EFFECT
(1+1=1)*Additive approach sometimes over/under
estimates the actual risk, but is still most accurate
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Super Topic 7: Ecological Risk Assessment
Ecological Risk Assessment: “Quantifying the PROBABLE EFFECTS of a wide range of human activities on
ECOSYSTEMS.”Analysis of ERA is difficult because…1. Many effects may be FELT ON A WIDE SCALE 2. Environmental Stressors like HUMAN INDUCED CHANGES3. Ecological efforts are INCOMPLETELY
UNDERSTOOD/HARD TO MEASURE4. Scientific knowledge in environmental decision making is
filled with UNCERTAINTY
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Super Topic 7 (cont.)
• Example: Snake River (Idaho)– Provided irrigation for agriculture1. Human-made changes: DAMS FOR ELECTRICITY2. Caused: NUTRIENT ENRICHMENT, WATER
TEMPERATURES, WATER FLOW3. Effects: algae and aquatic blooms FISH
POPULATION 4. Ecological risk assessment helps sets priorities to
meet the common goal of managing & protecting biological communities in the Snake River watershed.
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