Dissect three-dimensional models

Anveshna Srivastava

“Those who have dissected or inspected many (bodies) have at least learnt to doubt; while others who are ignorant of anatomy and do not take the trouble to attend it are in no doubt at all.” – Giovanni Battista Morgagni

As part of our biology practical classes, we all have been exposed to the concept of dissection, where we take apart biological organisms to understand their structure and function. Dissection has historically proven to be a very powerful device to understand biological systems, and remains a cornerstone of biology and medical education.

Dissection gives learners an unmatched view of the structural complexity and functional logic of biological systems. By dissecting frogs, say, under the tutelage of a helpful instructor, students learn to appreciate the intricate designs that natural selection has wrought over millennia, permitting these animals to survive climatic shifts that larger reptiles couldn’t.

But dissection is not just an exercise in natural philosophy. It also provides compelling visual answers to much simpler questions. Why are the kidneys where they are? How does the small intestine work? Observing biological elements in situ creates a natural setting for studying such questions, and allows learners to figure out many such answers by the simple task of identifying and taking apart the element in question.

I remember when I started dissecting flowers as part of my biology practicals, flowers ceased to be the usual ostentatious creatures. As we dissected out the male and the female reproductive parts from the bright red Hibiscus flower, I could not help but realize, perhaps for the first time, that plants were functionally as living as Homo sapiens! It still excites and fills me with awe to think about how challenging it was to finely dissect out the various floral parts and how those tiny structures were structurally so well-connected and functionally so competent as to sustain a complex life. For instance, Fig 1 is an immense close-up of the male reproductive part of the Hibiscus flower where little filaments are grouped together to form the stamen. One could only imagine as to how thrilling it would be for young hands to separate out the individual filaments without destroying the attached pollen sacs.

Figure 1: Macroscopic view of Hibiscus’ male reproductive part.

But what happens after dissection? Post-dissection, the respective organism is rendered non-functional but the dissectors develop a fair sense of its anatomical dispensation. Many consider that this trade off borders on criminality because you kill the organism in process. And the crime increases manifold when the organism in question belongs to the kingdom Animalia rather than Plantae. The reasons being the reckless killings of species (like frogs) which make them endangered and it is also argued that knowledge gained by dissection is not used by students post-college.

Hence, the University Grants Commission decided to ban animal dissections in zoology and life science courses in 2014 and a suggestion was made that students can use virtual media to understand anatomical dispensation and also carry out virtual dissections. This suggestion is not useful for twin reasons: a) Majority of Indian colleges and universities are not technically equipped to let students engage with computer simulations, and b) Doing things with one’s own hand is not same as doing it on a computer interface.

Replicating learning through the art of dissection
Learning through dissection happens when one understands the interplay of connected systems and dissects out what is required. This skill of learning can be transferred from functional systems to nonfunctional systems provided the latter reasonably approximates the complexity of the functional system and is also amenable to physical manipulation.

In this article, I talk about how manipulable 3-dimensional models can be used to play the role of non-functional systems that can be easily dissected upon in the classroom.

3-D manipulable models
Models or external representations can be used to depict an idea, concept, event, process, or system (Gilbert & Boulter, 2012). An interesting thing about models is that they could be designed within the constraints of the resources available to closely resemble the concept on hand. In fact, a small brainstorming session with students on resources that could be exploited to model a concept on can enable learners to engage with the concept more sincerely. Illustrate models of DNA made up of a sheet of paper, two parallel pencils, two anti-parallel pencils, a cardboard cut-out and clothespins. Such rudimentary models have been proven in the field to help greatly in explaining the three-dimensional structure of DNA.

Such models are not only simple to design, but they are also wonderful probing tools. An instructor can always design such instruments and engage learners to both probe and help them understand the concept at hand.

While models can certainly be used in point-and-tell lecture sessions, research shows that students learn better when they are allowed to work with the models themselves (Gillet et al., 2005). Manipulable models aid learning by allowing learners to incrementally construct the physical counterparts of complex ideas and processes. Instructors should, therefore, consider if and when to use such models when designing curricula.

A common way of using such models is to ask students to build it up from pre-fabricated components. Model-building is popular, but suffers from an under-appreciated problem. On the one hand, if instructors give students pre-fabricated parts that can be put together in multiple configurations, they have to attend intensively to them to ensure they are building it correctly. Using pre-fabricated kits with low degrees of building freedom permit instructors to be more hands-off since very few deviations from the canonical structure are possible, but simultaneously permit students to put components together purely as a mechanical task – with little conceptual engagement. Given the logistical constraints in most education settings, instructor time is usually scarce. So, schools and colleges err on the side of using models that are hard to build incorrectly. This inevitably leads to students mechanically building models, and not learning very much by doing so.

Dissecting 3-D models
Is there a solution? Yes, and a simple one. Models built from pre-fabricated elements can also be taken apart systematically and reversibly. Recent research has shown that model dissection is an interesting way to capture students’ attention along with tapping all the benefits of the art of dissection.

The dissection task can be delineated by the instructor based on which concepts she would like to explain, the resources available to construct or buy the required model and how much time she would like the students to spend on the task. The general format of the lesson would be to ask students to dissect out specified components from the given model.

And the model need not be necessarily complex. For instance, you can show how to make the ladder structure of the DNA molecule using knitting needles and styrofoam. Colored stryrofoam blocks represent the four nitrogenous bases (ATGC) and the phosphate and sugar molecules. An instructor could ask students to dissect out a series of components, viz., bases, sugar, phosphate, etc., from this model.

Discussion
The model dissection strategy is likely to work even better when students are informed beforehand that they need to re-build the model after the dissection task is complete. The students will then likely pay twin attention to the points of attachment between two components and the immediate neighbours of the component-to-be-dissected such that they do not pull out an irrelevant component.

Though the example I have taken is from molecular biology, instructors can use this method across subjects wherever they deem fit. The idea is to let learners engage with manipulable models in a focused fashion, without giving them too many opportunities to go astray.

References

1. Gilbert, J. K., & Boulter, C. (Eds.). (2012). Developing models in science education. Springer Science & Business Media.
2. Gillet, A., Sanner, M., Stoffl er, D., & Olson, A. (2005). Tangible interfaces for structural molecular biology. Structure, 13(3), 483-491.
3. Srivastava, A., & Ramadas, J. (2013). Analogy and Gesture for Mental Visualization of DNA Structure. In Multiple Representations in Biological Education (pp. 311-329). Springer Netherlands.
4. Srivastava, A. (2016). Building mental models by dissecting physical models. Biochemistry and Molecular Biology Education, 44(1), 7-11.

The author is a research scholar at Homi Bhabha Centre for Science Education (TIFR), Mumbai. She works on the interface of biology education and cognitive science. She can be reached at anveshna.sriv@gmail.com.