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A Mini-Lesson


Model, Model
Who's got the model?

(Formerly "Theory-Theory")

Michael L. Kimmel
ENSI 1991

Nature of Science

Social Context


A model-evaluation activity. A set of 5 models (proposed explanations for how diverse life came into existence on Earth) is divided evenly throughout the class, so each student is asked to evaluate one model. Students then come together in groups of 5, so that all 5 models are represented in each group, where the 5 models are compared and evaluated. Each group reports out to the entire class for further discussion and clarifications.


1. There are different ideas about the origin of life.

2. Science deals only with natural explanations.

3. "Theory" has different meanings in science and casual conversation.

4. Human values and personal biases can deeply influence science (its terminology, the questions asked, and the criteria used for choosing among different ideas).

5. The scientific view of the origin of life on earth is that it did not involve supernatural forces.


Student handouts (see below)

Teacher Materials:
- Key to model authors and approximate ages;
- References used to prepare features of each model


 (see end of lesson for the formatted handouts).

Sets of 5 different models (scenarios) for the origin of diverse life, enough so that each student gets one model to analyze.

Worksheets (3 pages) with tasks and questions for
- individual evaluation of a model
- group comparisons of 5 models


Worksheet Formats (2 forms for doing above in notebooks)


Because this lesson provides an excellent opportunity to understand important elements of the Nature of Science , be sure to read our General Background Information, with our Rationale and our Approach, and tips for Presenting the lessons for maximum effect and Dispelling some of the popular myths about science.

In any of the discussions expected with the class, select a few key items (important concepts) that lend themselves to interpretation, and introduce class to the Think-Pair-Share (TPS) routine dealing with those items. This is how "Active Learning" is done.

Do NOT reveal the authors or dates of the models until AFTER all classes have done the lesson! To do so may bias their conclusions.

Before or during this lesson, be sure that your students are aware of the proper distinction between model, theory, hypothesis, and a hunch or guess. If this was studied earlier, use this opportunity for review by asking what the different scenarios presented would be properly called: models, theories, hypotheses, or something else [depends; see under "Objections" below]. If not studied earlier, it would be good at some point during this lesson to discuss the proper and inappropriate usages of these terms. They are defined nicely on site by Martin Nickels in his paper on THE NATURE OF MODERN SCIENCE & SCIENTIFIC KNOWLEDGE: Scroll down to part IV of the paper, where these terms are defined.
It should be emphasized that the word "theory" as used in science should NEVER be used for any non-scientific explanation, e.g. a religious belief, or in reference to a casual hunch or guess, as in "it's only a theory" (even though this is, unfortunately, the common vernacular meaning). Also, because a hypothesis may, after some indefinite degree of confirmation, rise to the level of theory (or part of a theory), references to a hypothesis as a "theory" should be presented with qualifying quotation marks.

Keep in mind that a "model" as used here, referes to any description, diagram, or structure that shows how parts of an explanation are connected or related to each other. As used here, a model can include any scientific explanation (e.g., hypothesis or theory) or even a non-scientific explanation.

This activity can be used as 1) an opener, or early in your unit on the nature of science, or 2) later in the unit, following your explanation of how terms like "model," "theory," and "hypothesis" should be defined and used in science, or 3) opening a unit on the origin of diverse life.

In the first situation, after you have finished class discussion, you should point out that only one of the models is technically a scientific theory (Model D), for two main reasons: 1) no supernatural elements are included, and 2) it has been extensively tested and supported by the material (empirical) evidence. Models A, B, C, and E fail in both of those measures.

In the second situation, after class discussion of their evaluations, ask students to indicate which of the 5 scenarios is technically a scientific theory, and which are not, and the reason(s) for saying that (unless they have already pointed it out during discussion in the activity).

This could also be used as an opener to your introductory unit on evolution, as long as those clarifications are brought out and discussed as described above, or students can recognize those distinctions when prompted (or even voluntarily without prompting).

If there are objections to not considering "Model E", be sure to point out that it might very well be correct, but it cannot be considered as a viable scientific alternative mainly because it doesn't lend itself to the basic rules of science, which mandate that all explanations must follow natural processes (not supernatural), and must be subject to testing and rejection. For these reasons, the only scenario which can be considered for lengthy treatment in a science class is Model D. And, because Model E is a direct premise of an established religion , it is actually illegal to include it as a scientific alternative in any public school science class in the USA, as decided by the US Supreme Court.

1. Prepare enough copies of the 5 Models so that every fifth student gets the same model to evaluate individually (could be a homework assignment). This would be 6 copies of each page for a class of 30.

2. Prepare copies of "Individual Model Evaluation" forms, one per student.
Version 1: (1 page) is compressed, so there may be insufficient space for students to provide the requested information. You can simply have them do this on a separate sheet or notebook (using numbers for each item), OR...
Version 2: (1 page) has sufficient spaces for students to answer.

3. Prepare copies of "Group Model Evaluation" forms, so there is one for every group of 5 students.
Version 1: (1 page) is compressed, so students can copy format to their notebook or other paper. OR...
Version 2: (3 pages) can be used directly.

1. Distribute the 5 models so that each student has one. Then handout the "Individual Model Evaluation" forms, one per student. Allow some time for students to complete their evaluation forms (this would be a good homework assignment, if not finished in class). REMEMBER.... Do NOT disclose the authors or dates for the theories until AFTER class discussion.

2. After individual evaluation is completed, have your class form groups of 5, so that all 5 models are represented in each group, with at least one person with a completed "Individual Evaluation" for each model. Those who were absent, or who did not do the work, can be apportioned to different groups to sit in on the group discussions. If there are a few "extra" students (with their evaluations done), apportion them to existing teams (which will mean more than one evaluation has been done for one of the models, but that's ok). Try to balance out so all teams have only 5-6 students.

3. Each group must complete a "Group Model Evaluation" form, using discussion and consensus. Teacher can provide the "age" of each model when asked by a team (to answer question #3 on the evaluation form).

4. Finally, have each group report out to the entire class different aspects of their group evaluation, and engage in class-wide discussion. Teacher should make sure that the concepts (listed at beginning of this lesson) are accurately and clearly addressed during the discussion.

1. Additional scenarios could be added. For example, there are many interesting stories of creation in the great variety of primitive cultures in the world. One source for such stories, from which you could select one or two, can be obtained from NCSE. Just click to send an email asking for their flyer on "Origin Myths". Be sure to give your mailing address.

2. Dinosaurs are a constant fascination for kids, and the "asteroid impact" has become the popularly accepted explanation for their demise. Very few people realize that this is still hotly contested. For an interesting variation on the theme of this lesson, consider using dinosaur extinction as your focus. For an excellent discussion of the different hypotheses on the likely cause of this extinction, get Dinosaurs: The Science Behind the Stories, ed. by Judith Scotchmoor et al, published by the American Geological Institute (2002). Note especially chapter 12: Dinosaur Extinction: Changing Views (pages 99-106), where three hypotheses are presented and discussed. A very recent episode in this controversy was revealed in a Nature news article (10 April, 2003) in which new core samples from the reputed crater suggest an alternative explanation. Click here for a PDF copy of the brief article, along with a few review questions. For a more detailed presentation of this topic, go to our Model Choices lesson.

3. An even more recent study (2012) is reported on Science Daily site: “Dinosaur die out might have been second of two closely timed extinctions

4. New indications of gradual decline of dinosaurs before end of cretaceous period. Latest research results point to simultaneous rise in bird diversity
April 3, 2017, Heidelberg University
New research suggests that the gradual decline of the dinosaurs and pterosaurs presumably came before the impact of the Chicxulub asteroid and the global mass extinction at the end of the Cretaceous Period. Studies also indicate that bird species spread and diversified at the same time the dinosaurs disappeared.

The following were used as sources in compiling the information for this activity.
1. Biological Science: A Molecular Approach. BSCS Blue Version, D.C. Heath and Co. (5th & 6th editions)
2. Birx, H.J. Theories of Evolution. 1984. Charles C. Thomas Publisher.
3. Strahler, Arthur N. Science and Earth History: The Evolution/Creation Controversy. 1987. Prometheus Books.

Model A: Aristotle, circa 350 B.C.
Model B: Jean Lamarck, 1809
Model C: Empedocles et al, circa 500 B.C.
Model D: Charles Darwin, in his Origin of Species, 1859
Model E: "Scientific Creationism" John D. Morris and the Institute for Creation Research, circa 1960


Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

1. Original Source ("Theory-Theory"): Michael Kimmel, ENSI '91

2. Reviewed by: M. Nickels, C. Nelson, J. Beard: 12/15/97

3. Edited / Revised for website by L. Flammer 3/01

4. Added extension. to research showing dinos were gradually declining in numbers before the Chicxulub asterioid hit. Added 5/13/17



 Model-Model, 5 models

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