A Small Victory, but We Have a Ways to Go

About a year ago, I wrote a blog post about the pervasive misrepresentation of natural selection, not only in the mass media but also by professionals who should know better. My main problem is with the depiction of natural selection as an intentional process, as in “The cockroaches evolved a clever solution in order to avoid the pesticide” or “The cockroaches had to evolve in order to survive.”

Last week, my husband and colleague Doug Gaffin provided evidence from his class that this misconception is common, but that good teaching can start to turn it around. Before he began his unit on evolution, he asked the hundreds of students in his introductory zoology class to respond to several true/false clicker questions:

  1. Evolution results in progress; organisms are always getting better through evolution.
  2. Humans are the pinnacle of evolution and have stopped evolving.
  3. Evolution is not science because no one has observed it happen.
  4. Organisms adapt when needed so they can increase their survival.
  5. Natural selection gives organisms the traits they need.
  6. If humans evolved from apes, then all apes should have evolved into humans.

He asked the questions again after the evolution unit was complete. Most students (82-92% of them) already knew that #2, #3, and #6 were false before the unit even started; their responses were virtually unchanged in the “before” and “after” sessions.

Question #1 also showed virtually no change; about half of the students agreed with the statement before and after instruction in evolution. However, I find the question confusing. It is false because organisms don’t necessarily get “better,” whatever that might mean, and mutations will continue to occur. But it is also true because natural selection tends to weed out the harmful mutations. So that one doesn’t seem very informative to me.

The most interesting responses were to questions #4 and #5. Before instruction in evolution, a whopping 92% of students incorrectly agreed that “organisms adapt when needed so they can increase their survival.” Afterwards, that number dropped to 41%. The improvements were less dramatic for question #5. About 66% of students incorrectly thought that “natural selection gives organisms the traits they need” before the evolution unit started. Only 32% of students agreed with that statement after the unit was complete.

misconceptions
Both #4 and #5 get at the heart of the “organisms can evolve on purpose” misconception. On the one hand, it’s nice to see that good teaching can make a difference. On the other hand, it’s frustrating that more than a third of the students held onto that misconception even after weeks of instruction.

I will continue to look for resources and activities to help students overcome this difficulty. If you have any to share, please add them to the comments section. I thank you, as will your teaching colleagues.

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3 Responses to A Small Victory, but We Have a Ways to Go

  1. I cross-posted this blog post to iteach-biology.com, and I received these replies there:
    Response 1:
    Check out The Origin of Species video & worksheets at http://www.hhmi.org, available as downloads and DVD (free). The series on climate change is also fantastic; I’ve used the later in class recently.

    Response 2:
    I combine clicker questions with short group essay questions in my flipped, blended cell bio course. Here are a few questions that could serve in any bio course:

    1. Which statement below best defines the role of natural selection in evolution?
    a) It can result in beneficial new traits in a species when it needs them to survive.
    b) It can result in beneficial new traits in an individual when it needs them to survive.
    c) It can result in extinction of species.
    d) It accounts for the spread of beneficial traits from an individual to a population.

    2. Evolution is a long-term the response of living things to their environment by the process of Natural Selection. Natural selection actually selects (chooses)
    a. beneficial phenotypic traits existing in a species.
    b. phenotypic traits based on pre-existing mutations in individuals.
    c. genes that should be mutated to produce phenotypic traits based on environmental conditions.
    d. which different environmental conditions to respond to, and when.

    Discuss the following statement/proposition:
    Evolution is long-term, natural selection is immediate. Explain.

    Before I ask these questions I would have given formal definitions of all terms and discussed a bit about probabilities and how they figure in the nearly inevitable origins and evolution of life. All 3 questions will require discussion and debriefing. You could ask the group essay question first, discuss the answers and then use the clicker questions to see what students learned. Or ask the clicker questions first, allow discussion while answering, and then present the essay question. In my course, clicker questions earn participation credit and index card essay questions are signed, handed in and scored for grading.

    An alternative to Question 2 might be:

    The raw material of natural selection is
    a) all of the normal (non-mutant) genes in a species.
    b) all of the normal (non-mutant) genes in individuals in a population.
    c) all of the mutant genes in a species.
    d) all of the mutant genes in individuals in a population.

  2. Pingback: Two Outstanding Videos: One for Natural Selection and One for the Genome | Teaching nonmajors biology

  3. I think that question number one is not only confusing, but actually true, since evolution is not equal to mutation. It is the result of mutation and selection over time, so by definition it CAN only lead to “better” organisms.

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