12. Developing Understanding Through Model Based Inquiry

        The natural variation among humans, or even the students within a classroom, is a great starting place for starting the study of genetics and evolution.  At the heart of this understand is the careful collection of data and observation of their patterns.  This discipline shows two different models of inquiry: looking at data in the past (evolutionary biology) and that in the present (genetics).  


        The goal for this is to make students adept at identifying patterns in the variation and simiilarities in phenotypes found within family lines.  Several models are important for explanatory power: genetics models explian how genes interact to produce variations in traits; models of chromosome behavior  for the process during meiosis; biomolecular models to show the role of DNA in an organisms phenotype.  These three models and their relationship form a conceptual framework for understanding genetics.  

Attention to Students' Existing Knowledge

           The instructional design is influenced greatly by students' preconceptions and the difficulties they encounter in understanding.  Students view models in a naive realistic manner rather than conceptual structures that scientists use to explain data.  Following a study of student thinking about these models, the instruction was altered.  A subsequent study showed that these modifications helped students understand the conceptual structure.  
        Scientific modeling is complex.  It requires students to articulate a set of propositions.  To help them along, a modeling game is introduced at the beginning.  This takes 3-11 lessons, and involves a black box that spills out different material.  Students must collect data and ultimately create presentations about their theories.  After prompting and questioning, the teacher extends the students' thinking by explaining that to explain the invisible, scientists develop models.  The students then develop models to explain the situations they see.  With more presentations, the models become causal.  Then the teacher helps connect how these models are used to undesrtand how the natural world works.  What is key with a instructional activity such as this is to create a situation that is complex enough to create a model that is worthy of the rigor of scientific modeling.  
        It is also important to emphasize that science is a process of observing, imagining, and reasoning.  This way they see science not as truths to be memorized, but as understandings that grow.  Some other useful principles are allowing students to search for patterns in data, generating explanations (often through models), making predictions (based on the models), making and revising public ideas.  Even a simple activity such as the black box can serve to teach students the culture of scientific investigation.  
        After having exosed students to the modeling excercise, the instruction turns to genetics.  A set of data analysis activities required students to integrate across the 3 models.  Compared with at first (when this wasn't done), there was an improvement in students' undestanding of genetics.  An inquiry process was used.
Student Inquiry in Genetics

        During the first few days, students learn about the meiotic model.  In the introductory activity, students look at sets of pictures and are asked to determine which indiviuals are embers of the same families.  Next, after students develop some understanding of meiosis (with assistance from the teacher), they receive 3 packets of peas representing a parental generation and the F1 and F2 generations.  The peas are characterized by color and shape by the students.  Using what they know of meiosis already, the students recreate Mendel's simple dominance model. 
        Next, to reinforce their understanding, students use a computer program called Genetics Construction Kit (GCK), which allows students to manipulate populations of virtual organisms by having them mate.  They thus develop expertise in the simple domniance model.  
        At this point, the idea that models must be refined when data does not fit consistently with it is brought, as the simple dominance model does not include recessivenss.  After some direct instruction on certain concepts like transcription, translation, and protein function, students are put into groups and return to the computer program, only this time having to deal with new concepts.  After about a week of data collection, model testing, and team meetings, the students perform presentations on their new models to the class.  
Metacognition: Engaging Students in Reflective Scientific Practice

        Ultimately, students need to learn to reflect on and judge their own work rather than relying on assessments from others.  One mistake they frequently made was relying on empirical power over conceptual consistency (i.e. how one model can fit so much data, yet ignored how some data may be inconsistent).  As such, following modeling activities students were asked to rate themselves and others in various categories such as understanding the science.  


        The genetics class is very reflective of real scientific practice: students engage in extended inquiry in which they collect data, seek patterns, and attempt to explain those patterns using casual models.  


        The goal of this unit is a deep understanding of evolution - both how the knowledge is generated and how it is justified.  Different with the previous unit, this time students are engaged in historical evidence, opening the new challenge of not being able to replay the tape of human history.  

Attending to Significant Disciplnary Knowledge

        Some of the concepts, especially natural selection, are based on several prior understandings.  Also important is how Darwinian explanations are generated and justified.  

Attending to Student Knowledge

        There are a wide range of both conceptions and attitudes that students have on evolution.  In some ways, the scientific method used in evolution resembles history.  To develop a narrative approach, a significant amount of time is needed.  Many other methods require less than the 9 weeks needed here for this reason.  However, studetns ultimately end up with deep understandings of evolution.  

        All 3 principles are interwoven closely in the instruction of this unit.  At the beginning, a sequencing activity is conducted where students put pictures in order based on inferences they make.  This leads to a discussion of inferences, which is an important concept in evolution.  The initial discussion focuses on students' observations of the images.  It becomes clear quickly, however, that different students put different values on different considerations.  This leads to a discussion of inferences, which is generalized.  It leads to some ideas about how questioning and encouraging students to think and communicate is important.  
        The cartoon activity has specific instructional components too.  It shows how, like evolution, nondemonstrative inferences must be carried out, as well as how past events must be reconstructed.  
        To study variation, sunflower seeds are used.  Students count the stripes and note all the differences.  

Understanding the Darwinian Model

        Three different historical models that account for adaptation and diversity are considered by students.  In each case, students must examine the arguments, the major inferences drawn, and the data and prior knowledge used in the inferences.  The three models are Paly's model of intellignet design; Lamarck's model of acquired charactersitcs; and Darwin's model of natural selection.  At first, each model is examined on its own, with students discouraged from making comparisons.  Students read edited selections from the authors, asnwer questions, and participate in class discussions.  They are also given the opportunity to explore the natural phenomena.  For eample, they examine fossils discussed by Lamarck and dissect an eye to examine the structure/function relationships that fascinated Paley.  Next, they compare the three models.  Comparing the assumptions of each of the models helps them see what distinguishes between natural selection and the others - how there is a naturalistic mechanism of species change.  

Using the Darwinian Model 

        During the final weeks of the course, studetns create Darwinian explanations using components of the natural selection model.  Many sources of information, such as photographs, are used.  This is done through a series of case studies.  During each study, each grup must consult with another as they develop their explanations.  In such a way, students develop a narrative that draws on available data.  They also question one another.  This leads often to multiple interpretations and refinement of thinking and language use.  
        For the final case study, students must produce an explanation for sexual dimorphism observed between male and female ring-necked phesants.  They must develop research proposals that other groups must evaluate for funding.  


        By the end of the course, students reason in sophisticated ways about inheritance and evolutionary patterns.  This is due in large measure to careful attention to core disciplinary knoweldge, as well  as persistent attention to students' preconceptions.  The instructional activites highlight a classroom environment that is kowledge-centered in putting core concepts with scientific approaches together.  
        The use of frequent dialogue helped the teachers continually monitor students thinking and to make instructional changes to build on students' weaknesses.  
        Formal and authentic assessments were embedded.  This becomes possible when students constantly need to articulate the process of arriving at a solution.  There were also several formal assessments as well as many written tasks.  In the evolution unit, at the end students had to write a Darwinian explanation for the color of Polar Bears.  
        A scientific classroom community was built by collaboration and questioning being emphazised.  Using the model approach students were involved in an intellectual process.  Metacognitive reflection helped develop this at well.  
        This was all helped out by the idea of learning for understanding.  Most studetns know the "game of school" quite well, and are adept at memorizing and reiterating information.  Developing systematic ways for students to critique themselves and others' ideas contributed as well.  


              For students to develop deep understanding all four principles must be at play.  Even students in school can develop sophisticated and complex arguments.  There have been calls for studetns to be "engaged in inquiry" by the National Science Educaiton Standards.