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Pollution drives evolution in the Hudson River

Unit Plan: Natural Selection & EvolutionLesson: 6 Time: Varies. One to several class periods.
Setting: Classroom
9-12Hudson River Ecology
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Students will know how Hudson River tomcod evolved resistance to PCBs and be able to critically compare the way different news outlets choose to tell a scientific story.


    1. The teacher reads students the first lines of several science articles written for a public audience. All articles tell the ‘same’ story.
    2. Each pair of students chooses articles to read and together completes the critical reading worksheet.
    3. Discuss the stories and student answers as a class.


    • Copies of worksheet “Evolution and Pollution in the HR,” one per student
    • Copies of “Toxic river means rapid evolution for one fish species” (drafted by UC Berkeley, see “Explore” in Procedure)
    • Printed copies of newspaper articles (links to original articles provided  in “Explore”); ~10-15 each


    Engage students in a discussion of how we come to believe/ ‘know’ information.  Watch the following ATT commercial:[b1]   Ask:  How did these kids make their decision?  What do they think/know?  How do they come to believe it?  What role did the adult have in guiding the kids’ thoughts?  Who thinks the little girl may be right, even if she doesn’t know it—i.e. that maybe it’s good for a turtle to be slow? (Millions of years of evolution guided them to be that way, after all.)

    Ask students: Who thinks the sky is blue?  Ask them to explain their choice.  They may at first say yes, but then begin to question what at first appears to be such a simple fact statement.  Sometimes it’s red (sunset), greenish (tornado weather), etc.  You can also prompt them: Is it blue to someone who is colorblind?  How can we know if it is really blue?  Begin a discussion of how we can know/how we have come to believe that the sky is blue.  If a student responds along the lines of “because a lot of people agree that it is,” bring up the fact that for a very long time most people also believed the world was flat.  Sometimes even large groups of people are wrong.  Advanced students may reference spectral wavelengths, indicating that most of us perceive as ‘blue’ (or red, etc) the ‘blue’ portion of the light spectrum that reaches our eyes. 

    Finally, ask them:  How do you know something is true?  After discussing whether the sky is blue, they should mention things like observation, scientific studies, or authorities saying it is so.


    Tomcod evolution and PCB Readings 

    1. Toxic Avengers: Pollution Drove Fish Evolution, by Christopher Joyce (NPR)
    2. Hudson River Fish Evolve Toxic PCB Immunity, by Anne Minard (National Geographic News)…
    3. Did Pollution Drive Fish’s Evolution? By Lee Dye (ABC News)
    4. Waters of change: An accidental experiment in America shows how evolution happens (The Economist)
    5. Mutant fish safely store toxins in fat, by Janet Raloff (Science News)
    6. Toxic River Means Rapid Evolution of One Fish Species (UC Berkeley article):

    Hand out the student critical reading worksheet and instruct the students that this will be a science reading and discussion exercise.  Students should be given the option to work on it independently or in pairs/small groups.  They should also have the option to move to read the story out loud to each other if they choose, as some students learn/remember better by listening to a story or reading out loud. 

    Read the first-line prompts out loud from the PowerPoint.  The students/student groups should choose an article to read and complete Part A of the worksheet.  They should then be prompted to read a second article for comparison, after which they should complete Part B.

    Next, distribute the article from UC Berkeley “Toxic river means rapid evolution for one fish species.”  Students should read this article and complete Part C.

    Finally, discuss student responses as a group. Find out which articles they chose to read, which they liked best/least, and why.  Ask them what parts they still have questions about.  Have students answer each others’ questions when possible.  Discuss their thoughts about the story – what implications does the evolution of toxin resistance have for animals in other ecosystems? Can we depend on evolution as a solution to other human-caused environmental challenges, like climate change or species invasions?  What do they think are some of the challenges associated with writing about science?  How did these authors meet those challenges?

    ***These articles can be read as part of a group in one-two lessons, depending on the reading level of your students and the quality of the discussions that result.  Alternatively, you may choose to extend this activity over many days to give the students extra time to read the articles, if necessary, and to help break up the day’s activities.


    The Environmental Protection Agency (EPA) Superfund Act was passed by the U.S. Congress in 1980.  A national priorities list of abandoned hazardous waste sites that required long-term cleanup was established. 

    Foundry Cove was designated as a Superfund site due to the severe cadmium contamination.  Yet the current PCB Superfund project currently taking place in the Hudson River near Albany is vastly more complex than the Superfund project in Foundry Cove. PCBs are entering the river from many sources, rather than one source as in Foundry Cove.  The Superfund site at Foundry Cove was confined to that area, in contrast to the enormous span of the PCB Superfund project.  Today, 200 miles of the Hudson River is classified by the EPA as a Superfund site – one of the largest in the country.

    We spend a lot of money on environmental programs like EPA Superfund sites, yet many would argue that we should be spending much more if we hope to maintain ecosystem and wildlife health.  While it may seem obvious that there is a need to clean up areas where all or nearly all of the wildlife suffers, it is often harder to see the effects on wildlife of other human impacts, such as lower pollutant levels, climate change, or invasive species.  Most often, people only hear about some of these impacts through public news outlets.  Yet, there are inherent challenges in effectively communicating difficult topics to a general audience.  This exercise should help students understand some of these difficulties and think about how they may be able to overcome them. 


    Students should find another evolution story, where a plant or animal has been shown to evolve in response to some human-induced change (climate, invasive species, pollutants, habitat alteration, novel chemicals in the environment, etc).  They should read, compare, and contrast three popular science articles that tell the story.  They should be sure to address the following:

      • What is the author’s main point in writing the article?
      • What information differs among the three articles?
      • Which article do you think provides the most accurate information, and why?
      • From where do each of the authors get their information?

    To learn more about the Superfund program:

    To learn about Love Canal, NY, one of the first well-publicized cases of toxic wastes harming a community:



    Assess student participation by markings on their articles.  Assess their understanding by their answers to the worksheet and quality of class discussions.

    Lesson Files

    Evolution & Pollution in the Hudson River - Student Worksheet

    Benchmarks for Science Literacy

    1A Scientific World View, 2A Patterns and Relationships, 5A Diversity of Life, 5B Heredity, 5E Flow of Matter and Energy, 5F Evolution of Life, 7E Political and Economic Systems, 9E Reasoning, 11A Systems, 12A Values and Attitudes, 12D Communication Skills, 12E Critical-Response Skills

    NYS Standards

    MST 4- Physical setting, living environment and nature of science, MST 6- Interconnectedness of mathematics, science, and technology (modeling, systems, scale, change, equilibrium, optimization), ELA 1- Language to collect and interpret information and understand generalizations, ELA 2 - Language for literary response and expression, ELA 3- Language for critical analysis and evaluation, ELA 4 - Language for communication and social interaction with a wide variety of people
    Next Generation Science Standards

    Science and Engineering Practices

    Asking questions and defining problems, Engaging in argument from evidence, Obtaining, evaluating, and communicating information

    Cross Cutting Concepts

    Stability and change

    Disciplinary Core Ideas

    LS4B: Natural Selection, LS4C: Adaptation
    New York State Science Learning Standards

    Performance Expectations

    HS-LS4-2. Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment., HS-LS4-3. Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait., HS-LS4-4. Construct an explanation based on evidence for how natural selection leads to adaptation of populations., HS-LS4-5. Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increases in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species.

    Kali Bird, Cary Institute.

    Additional Resources: