As a high school science teacher, I often have to juggle the demands of helping students learn conceptually complex material while trying to maximize their engagement in the subject matter. Just as I want students to enhance their understanding of scientific concepts, I also want them to be attracted to their work, to persist despite challenges and obstacles, and to show delight in their accomplishments: the hallmarks of student engagement, as Schlechty (1994) defines it.
It's not an easy task! In past years, I took a traditional approach with a complex but vitally important scientific concept: What is DNA and how does it contribute to genetics and the diversity of life? In past years, I usually presented material to students through lectures and labs. I explained key scientific discoveries and told students about the theories that resulted from the research. After presenting the material, I expected students to understand the relationship among DNA, RNA, proteins, and genetics. Although many students did, others did not; moreover, my students did not exhibit high levels of student engagement.
Last year, however, I redesigned my approach to teaching DNA in my 9th grade biology class, and, much to my delight, my students exhibited all of the defining characteristics of student engagement.
The catalyst was my school district's participation in the Thoughtful Education Program (Hanson, Silver, and Strong 1990). This program describes four dimensions of student engagement, and it provides training to help teachers boost student engagement in their classrooms. The first dimension is rigor. Students want and need content that challenges their minds and stimulates their curiosity. Provocative, demanding content is more motivating to work on than simple, unambiguous material that skims the surface of ideas.
The second dimension is thought. Students want and need activities that challenge them to think and develop understanding. Assigning routine tasks that require only low level thought rarely engages students in learning. Costa (1991) contends that thinking is what you do when you do not know the answer. Thinking is an engagement of the mind that changes the mind.
The third dimension is self expression. Students need opportunities to express their originality in their work. School often thwarts this drive by requiring everyone to do the same thing, and by providing few opportunities for students to choose the medium in which they wish to work. Students have too few opportunities to produce genuine, original, creative products that demonstrate what they know and understand.
The fourth dimension of engagement is authenticity. Students need to see the links between the material they're studying and the real world, and to make connections with their own experiences. Therefore, the tasks we ask students to carry out should, to the extent possible, be connected with the world of work, academe, the arts, and local communities.
A Thoughtful Approach to DNA
After learning about the Thoughtful Education Program and thinking about how I might reflect its ideas in my class, I decided to use these four dimensions to design a unit that would truly engage my students in the topic of DNA and diversity.
The central strategy I used for the unit on DNA is called the Mystery Strategy (Silver and Hanson 1994). The Mystery Strategy builds on students' curiosity, encouraging them to think like scientists. It calls for confronting students with a deep, rich problem or challenge. Students are then provided with actual clues that scientists have used to build their understanding of that question and construct a response. As in the real world, the information students receive is fragmentary and, in some instances, contradictory. The students must collect and organize the data, formulate tentative hypotheses, and use the data to support or refute their hypotheses.
- Present the mysterious event or "hook." (This could be a strange phenomenon, a question that puzzles, a secret that intrigues, or a riddle to be solved.)
- Supply the evidence and the clues. (During this phase, students must organize clues, make inferences, establish patterns, draw conclusions, and seek cause and effect relationships.)
- Establish an explanation. (Students form a hypothesis, select and refine that hypothesis, test the hypothesis, and build support for the hypothesis.)
- Evaluate the investigation. (In this phase, students reflect on the process, evaluate the hypothesis, and determine the effectiveness of the investigation.)
Building on the format of the Mystery Strategy, I designed the unit of study that follows. For me, the lesson design was a risk. I wasn't at all certain that the students would be capable of grasping such complex material without direct instruction. Also, I suspected that this strategy would take more class time than the techniques I used in past years. In fact, our class spent 10 class periods on the unit, compared to 4 to 6 periods before. But I believe the additional time paid dividends in the depth of knowledge students gained.
On the day the lesson was introduced, I posed the central question to students: "What causes diversity in living organisms?" Students wrote their preliminary ideas. Responses from this quick preassessment indicated that most of the students had little background in DNA theory or had never made any connection between DNA and diversity.
The Event
Next, I presented students with the following scenario:Dr. DNA, a leading microbiologist and geneticist, received a grant from the National Science Foundation to research the question, "What causes diversity in living organisms?" After years of study, Dr. DNA was finally ready to present her findings at an international symposium on the causes of diversity to be held in Washington, D.C. Scientists from all over the world gathered to hear her theory.As she was crossing the street from the hotel to the convention center, however, she was struck by a bus and killed. The scientific community was stunned, not only by her sudden death, but also by the loss of her work. The only hope for recapturing the results of her work were the scattered notes found at the scene of the accident.The National Science Foundation has decided to fund several more groups of scientists in an effort to reconstruct Dr. DNA's work. You and your teammates have been chosen for this honor.
The Evidence
In determining what information I needed to give students, I first wrote out my own explanation based on what I knew and understood. Once I established the important ideas I wanted my students to discover, I was then able to generate specific clues. The quality of the clues is critically important for this activity. A good clue should provide specific, observable data but should not provide much explanatory language.
For this unit, I developed 24 separate clues (Dr. DNA's notes), typed them on separate strips of paper, and distributed them to student teams. Teams began by reading the clues and beginning to sort them into categories. For example, many teams developed a category called "bases," under which they put such clues as "The order of bases is different from one organism to another." By manipulating the clues, students discovered that only certain bases could fit together. This was a crucial finding, because it helped students begin to understand the basic structure of the DNA molecule. Later, they would be able to connect this basic structure to the way the genetic code is controlled by DNA. After sorting their clues, students began to analyze their data. They spent a considerable amount of time discussing the clues with their team, reading the textbook for relevant information, and consulting with me. Each team took observation notes and kept a journal, and the entries teams made revealed some of their thinking as they tackled the mystery. For example, one team's journal entry read:If different organisms have different amounts of DNA, then they must have different amounts of the four building blocks. The bases will still pair the same way, however, because adenine always pairs with thymine and cytosine always pairs with guanine.We are wondering about the order of bases. Does it change from organism to organism also? If it does, maybe that partly explains why the clue "DNA is able to make exact copies of itself" is important. We are also seeing some kind of connection between DNA, RNA, and proteins. Not sure what this all means yet, but we still have lots of clues left to sort.Later these same students wrote:Having looked at a number of clues today, we now think the order of bases in DNA guides the manufacturing of RNA in a cell. The RNA guides the production of proteins in the cell. The amount and types of proteins that an organism is composed of help to identify the organism. WOW! Can you believe it? I never knew the order of four bases could be so important! We now need to look for some experimental evidence that proves our ideas.
As the journal entries suggest, students were learning to build their understanding in much the same way that a scientist would. They sorted, recorded, and analyzed their clues and data for relevance to the solution. Every tentative answer led to another question to be pursued. As one student said, "Solving this mystery was like being in a haunted house. You knew there was a way out, you just had to find it!"
The Explanation
Once teams had reviewed, sorted, and analyzed the data, they were ready to formulate their hypotheses. Drawing upon experimental data, students had to develop a hypothesis about what causes diversity in living organisms. For example, one team's hypothesis stated:The chemicals that make up DNA are adenine, guanine, cytosine, and thymine. These are arranged in different patterns in the DNA molecule. These patterns cause diversity by passing their code to RNA, which carries DNA's message to the ribosomes where proteins are made. The making of different proteins in different organisms causes diversity.
Most teams rewrote their hypotheses several times before being satisfied with the result, and I found that while students were quick to recognize DNA as the cause of diversity, they found it more difficult to cite the evidence that supported their ideas. Nevertheless, students as a whole demonstrated a deep understanding of the complex material of the unit. Taking fragments of information, they made connections and constructed meaningful hypotheses about the diversity of life.
The Evaluation
As a final product for this project, each student team presented an oral report at a simulated international symposium, accompanied by a visual tool designed to enhance the presentation. I worked with my classes to develop the criteria they would use to evaluate their work, and we agreed that it should be judged on content (understanding of the concepts presented), critical thinking (ability to develop a coherent and comprehensive explanation using the clues), and communication (ability to use both visual and oral formats in a clear and meaningful manner). We developed indicators for each criterion, so each team would have a clearer picture of how its work would be assessed.
Soon, the teams were ready to present their theories. We created programs announcing the "First Annual Symposium on the Causes of Diversity in Living Organisms," distributing them to all on the day of the presentations.
Each team's presentation gave me an opportunity to clarify and elaborate on the topic. I asked students to record the main points made during each group's presentation, especially noting the presence (or absence) of experimental evidence. By the time we reviewed all of the presentations, students had a clearer picture of the process scientists use in their work and an understanding of DNA and the role it plays in the diversity of life. Because students constructed the knowledge for themselves, they had a solid understanding of both the vocabulary and the concepts. In the weeks that followed, they retained the information and were able to recall the clues and the concepts as we continued our study of genetics.
Content and Process
By using the four dimensions of engagement to guide my planning, I was able to meet both my content objective (students enhanced their understanding of DNA theory) and my process objective (students displayed the ability to collect, organize, and manage information in order to develop a thoughtful theory supported by evidence).
As I began this lesson, I struggled with the fact that I would be placing a greater emphasis on the process, as I allowed students to construct knowledge for themselves. Would students learn the content if I did not provide them as much information up front? I learned that carefully planned, inquiry based teaching strategies that call upon students to make sense of concepts and data can be every bit as effective as more traditional approaches. Moreover, the processes I used generated a high level of student engagement and motivation.
