Models in science are never really "final", but in the classroom, there are times when we need to put a "period" (or at least a "comma") on our model so that we can move on to new phenomena and ideas. Working through the process of finalizing the model with your students can be tricky, especially if there are ideas that still need to be evaluated or even generated before you are ready to do so. Here are some tips for handling pieces of this process that teachers have found useful.
1. How do you guide the class to settle on a “final" working model?
- First, note that there is no final model. Models are always subject to revision in the light of new data.
- Once you have completed all of the activities designed to test and deepen the model, the class decides whether or not further revisions are needed. To do this, we direct the class to consider whether or not our model meets the model criteria:
- Does it fit our data and explain our observations?
- Is it realistic/plausible, given what we know about the natural world?
- Using it, can we make accurate predictions?
- This last point may require that you explicitly generalize the model. You may have been working with terminology and ideas very specific to the phenomenon at-hand. Here it can be very productive to try and create more general statements that still reflect the model ideas.
- Note that any re-evaluation of the model is not a discussion about what is right or wrong, but a judgment as to what is best based on the criteria. Because the model ideas came from the whole group, no one is personally associated with them and there are no hurt feelings if an idea is discarded or changed. Our goal is to develop the best possible model for the benefit of all.
- Once everyone is happy with the model it is considered “final” (unless future evidence suggests it should be revised). You can use a number of strategies for determining when the class is happy with the model such as five-finger voting.
- Note that we still refer to it as a "working model" because all models are subject to change if new evidence arises.
2. What do you do if students are happy with the model but you know there is still something missing?
- In this case you may need to ask some probing questions to help students see that the model does not have all the ideas needed to answer the original question. You may need to find another activity, reading, or video to provide the information students need to complete the model.
3. What if there is an idea in the model that the class cannot agree upon? For example, some people think the idea belongs in the model, but others think it should be eliminated.
- Generally you would want to leave the idea in, but with a question mark. There is a very good chance that at some point new information will arise that enables the class to revisit the idea and re-evaluate. If you feel the idea is going to cause problems for students as they use the model to write explanations, you will need to bring in other evidence NOW that will help students resolve the disagreement. This evidence could be in any of a number of different forms: a reading, data sets, videos, demonstrations.
4. What do you do / can you do with the model now?
- Models in science do not work in isolation: they are inextricably linked to one another (which made developing a linear model-based curriculum extremely challenging!). Any model can be connected to others, and this provides incredible opportunities for students to make connections across the curriculum.
- Be ready to revisit models as the year goes along. Some models, such as Natural Selection, are revised very intentionally as student understanding of biology deepens throughout the year. Others may not be so directly re-addressed, but the opportunities are there should you want or need them.
- Classroom models are ALWAYS subject to revision. (Are you sensing this point is important?) Be prepared for both planned and spontaneous revisions as student ideas or understandings shift in light of new phenomena. This is how science works. Our understanding of what's going on with the universe shifts as new data is generated, new observations made, new patterns recognized. This is the exciting part of science: we may never get to a complete "right" answer!
- A "final" list of model ideas is NEVER to be the subject of an assessment. The ideas are tools for students in their evaluation of natural phenomena. If you want to test their understanding of a model, why not give them a pattern or phenomenon and ask them to apply appropriate models. Alternately, you can give them a scenario (phenomenon) and ask which model ideas apply. Some teachers allow students to use their "model summary" sheet as a "cheat sheet" for such exams. Importantly here we are evaluating student understanding of how to use model ideas, not their ability to memorize the components of a model.