Class content >Introduction to the class

In order to become a biologist or health-care professional you have to study a variety of scientific disciplines -- biology, chemistry, physics, and math. You might have noted that the world doesn't actually divide itself in this way.  Rather, the disciplines are a way of choosing a sub-class of the phenomena that occur in the world and looking at a particular aspect of them with a particular purpose in mind. The different disciplines have different sets of tools and ways of knowing. Looking at something from different disciplinary perspectives adds a richness and depth to our understanding -- like taking two 2-D pictures and merging them into a 3-D image.

Your introductory science and math classes often provide you with some basics -- tools, concepts, and vocabulary -- but may not give you a perspective on what each discipline adds to what you are learning and how they all fit together.  Each discipline has its own orientation and perspective towards the development of a professional scientist.  Here's a brief (and oversimplified) overview of the different disciplines that you encounter in studying biology.

Biology

Biology, as you well know, is the study of living organisms. The approach taken by biology is guided by and constrained by the fact that the subject is about living organisms.

• A lot of biology is complex  -- Because of the complexity, the first step in biology (and in other sciences of the complex) is often about identification, classification, and description of phenomena. Whenever a science considers a complex phenomenon it does this -- whether it's biology, organic chemistry, or plasma physics. In biology, it is important to describe the traits, structure, and behavior of a biological phenomenon before looking toward mechanistic explanations of how it works. So it was important to do Linnaean classification and morphology before the ideas of evolution could be worked out; and an understanding of the nature of organic chemistry and biological molecules was necessary before the molecular functioning of biological systems could be disentangled. This results in biology having a huge vocabulary and many concepts to learn.
• Biology is fundamentally historical -- By this we don't mean the history of how the science of biology developed, but the history of how organisms developed. What has happened over time matters in biology and affects how things are today. This is like geology, and unlike chemistry, physics, or math. (Though when biology gets down to the mechanism of how things actually happen it is very like chemistry and physics, and uses math.)  The properties of organisms that are currently alive and their relationships to their environments and to each other depend a lot on what happened to their ancestors in the distant past. The history of an organism is written in its genome. One cannot "explain" why a particular organism solves a biological problem in a given way without knowing how evolutionary processes have shaped the solution.
• Biology looks for mechanism -- Biology is not just about "What is life?", but it's about "How does it work?" At one level, one might look at the organs and parts of either an animal or a cell and figure out what their function is for the organism. Today, using the tools of chemistry and physics (and using math), modern biology goes down to the atomic and molecular level, figuring out how an organism's genome leads to the biochemistry that helps understand the functioning of life at the most basic level.
• Biology is multi-scaled -- an organism can be considered at the atomic and molecular scale (biochemistry) and internal structure and functioning of its organs and parts (physiology), and as a part of a much larger system both in space (ecology) and time (evolution). The relation between these scales can be treated by reductionism or emergence -- going to smaller scales to explain something or seeing new phenomena arise as one goes to a larger scale.

Because of the built-in complexities of biology, the teaching of biology at the introductory level tends to be organized by phenomena rather than by principle. But professional biologists and health care professionals have to take a broader and more integrative view; in particular:

• Biology is integrative -- Biological phenomena emerge from and must be consistent with the principles of chemistry, physics and math. Therefore biologists must understand these more fundamental principles, and understand how they manifest themselves in biological processes, organisms, and higher order systems. Increasingly, biologists build mathematical, physical, and chemical models of biological processes, and test those models by studying biological organisms.  Biologists can approach any given problem from many different levels. A given researcher might focus on one level or another, but the whole of biological sciences integrates these levels.

Chemistry

Chemistry starts with the idea that all matter is made up of certain fundamental pieces - atoms of about 100 different kinds (elements) - and is about the ways those elements combine to form more complex structures - molecules.  But chemistry is not just about building molecules.  It's about what you can do with that knowledge in our macroscopic world.

• Chemistry is about how atoms interact to form molecules - This is the basic fact that defines what chemistry is about. Understanding the basic principles of how atoms interact and combine is a fundamental starting point for chemistry.
• Chemistry is about developing higher-level principles and heuristics - Because there are so many different kinds of molecules possible, chemistry develops higher-level ideas that help you think about how complex reactions take place.
• Chemistry frequently crosses scales, connecting the microscopic with the macroscopic, trying to learn about molecular reactions from macroscopic observations and figuring our what is possible macroscopically from the way atoms behave. The connections are indirect, can be subtle, and may involve emergence.
• Chemistry often assumes a macroscopic environment - Much of what chemistry is about is not just idealized atoms interacting in a vacuum, but is about lots of atoms interacting in an environment, such as a liquid, gas, or crystal. In a water-based environment, the availability of H⁺ and OH^- ions from the dissociation of water molecules in the environment plays an important role, while in a gas-based environment, the balance of partial pressures is critical.
• Chemistry often simplifies -- selecting the dominant reactions to consider, idealizing situations and processes in order to allow an understanding of the most salient features.

For a chemist, most of what happens in biology is macroscopic - there are lots and lots of atoms involved - even though you might need a microscope to study it. In introductory chemistry you often assume that reactions are taking place at standard temperature and pressure (300 K and 1 atm).

Physics

The goal of physics is to find the fundamental laws and principles that govern all matter -- including biological organisms. Those laws and principles can lead to many types of complex and apparently different phenomena. But the approach of physics has traditionally been to establish strong principles that hold very broadly and that can be used as touchstones (or in our "safety net" metaphor, as "stakes in the ground") for a wide variety of situations. Physics as traditionally taught at the introductory level tends to do four things that may seem different to biology students from what they see in their biology and chemistry classes. Biologists and chemist do use these approaches, but perhaps not to the degree that physicists do, and these approaches often are not made explicit in introductory biology and chemistry classes.

• Physicists often spend a lot of time working out the simplest possible example that illustrates a principle, even if that example is not particularly interesting, relevant, or realistic. This permits the physicist to understand clearly and completely how the principle works.  This understanding then can be woven into more complex situations to produce a better sense of what's going on, although the imbedding of the simplicity in a realistic, relevant, and complex situation is often omitted in introductory physics classes.
• Physicists quantify their view of the real world. Although there is a lot of conceptual and qualitative reasoning in physics, physicists tend not to be satisfied until they can quantify what they are talking about. This is because purely qualitative reasoning can sometimes be misleading. While you can come up with an argument that says A happens, if you think carefully, you might also come up with an argument that says something different happens -- B. It's not until you can figure out that effect B is 1000 times bigger than effect A do you really know how to describe what's going on. This is just as true in biology and chemistry as physics, but physicists tend to introduce quantification sooner in the curriculum and more extensively than chemistry, which does it more in introductory classes than biology does.
• Physicists think with equations. This is more than just calculating numbers: physicists use equations to both organize their qualitative knowledge about what affects what and how, and to reason with in order to determine how things happen, what matters, and how much. Physicists go back and forth repeatedly between thinking conceptually about a problem and thinking mathematically about a problem, so that each of these ways of thinking sheds light on the other.
• Physicists deal with realistic situations by modeling and approximating. This means identifying what matters most in a complex situation and building up a fairly simple model that lets you get a good picture of what's happening. This is where the art lies in physics: in figuring out what can be ignored without losing what you want to look at. Einstein got it right when he said: "Physics should be as simple as possible, but not simpler."  All sciences do this, but because physics is about "anything and everything", physicists often assume that they can get away in introductory classes by choosing systems that may seem to be simplified to the point of irrelevance. In this class, we'll try to be more explicit in modeling complex examples than in traditional physics classes.

This way of doing science is a bit different from the way biology is often done -- but elements of this approach and the constraints imposed on biology by the laws of physics are becoming increasingly important both for research biologists and health-care professionals. For more discussion, see the page, What Physics Can do for Biologists.

Math

Math is a bit different from the sciences. In its essence it is about abstract relationships.  Since math is about abstract relationships and how they behave, it's not "about" anything in the physical world. But it turns out that a lot of relationships in science can be modeled by relations that obey mathematical rules, often very accurately. (If you think this is surprising or strange, you aren't alone. For fun, take a look at the interesting article by the Nobel Prize-winning nuclear and mathematical physicist, Eugene Wigner, entitled, "The Unreasonable Effectiveness of Mathematics in the Natural Sciences.") 

Math as taught in math classes often is primarily about the abstract relationships -- learning how to use the tools of math. Making the transition to using math in real-world situations may be quite jarring as there are now additional things to pay attention to other than the math itself -- such as figuring out how the elements of the real-world system get translated into a mathematical model and worrying about whether the mathematical model is good enough or not. For more discussion of this, including details about particular places where students often get into trouble using math in physics (and in biology), read our pages on Modeling with Mathematics and our recap of the mathematics that will be used in this course.

Bringing these all together to permit coherent and productive thinking is a challenge! In this class we expect and encourage you to bring to bear knowledge you have from your other science classes -- to try to see how they fit together, support each other, and to learn to identify when a particular disciplinary approach might be most appropriate and useful.

Joe Redish and Joelle Presson

Modified in response to comments from Chris Bauer, Cynthia Bauerle, Catherine Crouch, Peter Shawhan, and Julia Svoboda. 7/22/11