When beginning secondary education in science the physicist may discuss energy, or forces, possibly even motion, the chemist may discuss the particle model. In these cases, such as the model of energy stores, or the particle model, the curriculum is intending on providing an early model for students which should serve them in attempting explanation of phenomena they are likely to encounter in their lives, and in the curriculum.
How should a secondary biology curriculum begin therefore, if not with an explanatory model? The hitherto most common forms of Y7 biology curriculum in England appear to begin with the notion of MRS GREN and Cell Theory. But are these explanatory?
MRS GREN, for a Y7 student, presents little more than a list of activities observed in life, but which, as Brett Kingsbury elegantly writes here, are arguably observed in other things such as fire, and don't apply so well outside metazoans. The list also presents considerable cognitive load with new vocabulary and new concepts. In all, students are unlikely to be able to link such a list to well-organised schema of knowledge, and thus, result in rote learning. But, let's say a student is able to incorporate MRS GREN meaningfully into their knowledge structures, is it explanatory? It tells us nothing of why living systems exist, nor how they work, thus it is merely descriptive.
Cell theory is a necessary concept for understanding biology, but it isn't sufficient, even at the age of 11. In fact, it isn't really a theory at all as it lacks explanation, it merely states that living systems are composed of cells and come from other cells. Thus, it is more a principle of life. It is also commonly accompanied by a selection of examples of components of the multicellular human and plant (see my post here for an argument on this).
Beginning biology in this manner must contrast sharply with the physicists and chemists' attempts at giving their students their ability to interpret their world meaningfully.
Consequently, the biology curriculum must seek to present, from the outset, an explanatory model. It must have good range (one that can be used throughout most of secondary education before being modified), and good match (presenting a generally faithful account of phenomena). Our choice here is not trivial, as with the topic of energy in physics, we should intend to present students with a framework that should serve them well with the concepts they will soon encounter in the curriculum, and in their lives.
An explanatory model, fit for all levels of biology education
Autopoiesis, a theory proposed by the Chilean scientists Humberto Maturana and Francisco Varela (in the 80s), fits the bill perfectly, in my opinion. In its most basic form, it explains that life is a system that shows self-maintenance, and self-creation (from within) by drawing upon flows of energy and matter. The theory principally discusses life at the level of the cell, considered the fundamental unit of life, and so describes how a cell functions to continually build and replace its component parts (in the correct organisation), be them phospholipids of the cell membrane, its molecular machines, such as ribosomes, or cilia, or the cell's environment and its gradients. But its utility for explanation in the biology curriculum stems from its ability to be applied at every level of organisation. We can see the same phenomena at the level of cells, organs, organ systems, and organisms, etc. For example, just as cells continually replace phospholipids, humans are said to entirely replace their cells every seven years or so; the system outlives its components. Luigi Luisi (2003) summarises it as 'A system can be said to be living if it is able to transform external matter and energy into an internal process of self-maintenance and production of its own components.' (emphasis my own).
Here is an image which can be used with Y7 students in the first biology lesson, which serves as a springboard for discussing humans at the organismal level (no need to go to cells yet), linking an abstract concept to their daily lives.
Many discussions can arise here, from why we breath, why we eat, wound healing, what we are made of (food), growth, et cetera. It has the power to, on a simple level, help students explain many things and easily access new biology contexts. It is explicitly inviting students to view life in terms of flows of energy and matter, but it is just the beginning, as it is the framework for the rest of the curriculum, be it at the level of cells, or organisms, that gains in complexity as students gain in expertise.
Epistemic views of biology
Why do students struggle with the concept of plants containing both mitochondria and chloroplasts, hence carrying out both respiration and photosynthesis? I propose they do so because they do not view life via flows of energy and matter, but have obtained a epistemic view that biology is descriptive and attempt to rote learn the appearance or not of components. There is nothing explanatory about knowing where mitochondria and chloroplasts are found without a knowledge of energy and matter flows. Thus, autopoiesis is an important primer for understanding plants as living organisms that show the same general patterns seen in other organisms, and that we are all connected via the cycling of matter and the flow of energy at ecological scales. Life is a process, rather than an entity.
Natural selection
Of course the last piece in the puzzle is to ask students what the point of it all is. Why do these living systems appear to purposefully procure energy and matter in order to create and maintain? And here, in the first lesson we can complete our framework that should serve us well; we can begin talking about natural selection. Of course, we do not need all the details, the model can increase in complexity throughout the curriculum, either gradually, or at specific times, but we can begin with the general idea. Which organisms survive, which reproduce, and which characteristics therefore predominate in the population. What would happen if an organism has no intentions of reproducing, or simply is too slow at doing so? These questions open a world of discussion, and are quite intuitive at a simple level. The great ramifications of natural selection will be a concept learnt over great periods of time, but I begin with the mechanism, in layman terms, on day one.
A curriculum grounded in explanation
Let us move on from a descriptive biology, and begin giving students the frameworks that will allow them to immediately interpret the world around them, and prepare them for the coming concepts of the biology curriculum. MRS GREN is problematic in many ways, and Cell Theory is insufficient alone. The cell's place in the curriculum is fundamental, but simply knowing the cellular nature of life is not enough. Cells are not static, they are dynamic, they are happening, and life emerges not from having cells, but from processes and interactions.
Biology specialists may agree that concepts such as structure and function, surface area to volume, the maintenance of gradients, entropy, et cetera, are all of paramount importance to understanding biology, but really, underlying them all are the concepts of energy and matter flows, organisation, and natural selection. Concepts that should never be out of sight, and should made explicit at larger scales of curriculum. If you've enjoyed this—check out my book. Download chapter 1 here—English edition—edición española—or check out my other posts.
Christian Moore-Anderson
@CMooreAnderson (twitter)
References
Luisi P. L., 2003. "Autopoiesis: a review and a reappraisal." Naturwissenschaften. 90:49–59.