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Chapter 1: The Study of Life

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The Scientific Study of Life

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Every systematic science, the humblest and the noblest alike, seems to admit of two distinct kinds of proficiency; one of which may be properly called scientific knowledge of the subject, while the other is a kind of educational acquaintance with it. For an educated man should be able to form a fair off-hand judgement as to the goodness or badness of the method used by a professor in his exposition. To be educated is in fact to be able to do this; and even the man of universal education we deem to be such in virtue of his having this ability. It will, however, of course, be understood that we only ascribe universal education to one who in his own individual person is thus critical in all or nearly all branches of knowledge, and not to one who has a like ability merely in some special subject. For it is possible for a man to have this competence in some one branch of knowledge without having it in all.

It is plain then that, as in other sciences, so in that which inquires into nature, there must be certain canons, by reference to which a hearer shall be able to criticize the method of a professed exposition, quite independently of the question whether the statements made be true or false. Ought we, for instance (to give an illustration of what I mean), to begin by discussing each separate species-man, lion, ox, and the like-taking each kind in hand independently of the rest, or ought we rather to deal first with the attributes which they have in common in virtue of some common element of their nature, and proceed from this as a basis for the consideration of them separately?

Aristotle, On the Parts of Animals Bk I (translated by William Ogle)

Why Study Biology?

One could choose Aristotle's first reason: that any truly educated man should have some understanding of every branch of natural philosophy, which means that he would study living things as part of the process of becoming "educated".

We might also be persuaded by the Judeo-Christian conviction that God created the universe and that humans are responsible for the care of this natural world, so it behooves us to study nature to understand its Creator, and to understand its complexities, so that we may act wisely and well as its stewards.

Even those who don't find a religious obligation compelling may be persuaded that the interconnectedness of the modern world makes it a survival tactic to pay attention to how industrial activities and biological research shape and change our world, and render it more or less inhabitable.

Of course, you may simply want to add a biology lab course to your curriculum in order to satisfy graduation requirements or college entrance expectations. If so, I hope that we can change your perspective a bit, so that the study of living things becomes a life-long pursuit, whether you do it professionally or merely as Aristotle's "educated" person, because you enjoy knowledge about many subjects for its own sake.

On a practical level, we need to determine the best ways to study biology. Modern biology textbooks often chose the second of Aristotle's proposed methods of education. After setting some limits on our subject to living things which share characteristics of cell structure, metabolic functions, and genetic inheritance, we will look at details of those most common characteristics — atomic structure, organic molecules, the components of those very cells, and the way they employ energy to perform their functions — before we undertake the study of different forms of life.

In order to start our study, we need to try to establish, if we can, what we mean by science and life, and form a plan for studying living things.

The Scientific Method

Scientists like to claim that they follow methods which eliminate error and depend solely on logical and rational examination of observation. In reality, scientists have their favorite theories, and are under many nonscientific pressures which often dictate what they will study and how they will make observations, take surveys, or perform experiments.

A simple example: Karl Popper, who is a historian of science, found in his interviews with British scientists in the 1950s that they often had a very good idea of what their experiments ought to prove, and designed them accordingly. How does trying to prove a specific hypothesis differ from trying to distinguish between two competing hypotheses?

A more complex one: some astronomers recently claimed that a rock (which they believe originated on Mars, not Earth) shows signs of ancient bacterial life. How might this claim affect the ability of xenobiologists (biologists who look for extraterrestrial life) to conduct experiments? Since government funding is a limited resource, what may happen to other investigations that have been planned?

As you read your text, keep the questions in mind about science in general, and biology in particular:

[I use the generic he throughout my lectures for grammatical simplicity only; I would personally take serious exception to the idea that women can't be good scientists!]

One approach to handling the masses of information about the natural world that we have collected over the last four millennia is to break down the complex systems we see into their component parts, since it is often easier to see common characteristics at different levels of organization. This approach is reductionism, and it is a very useful tool in science. In biology, we start with the whole region in which life can be found: the biosphere, and work our way through successive levels of organization until we reach atoms, the common structure shared by both living and non-living matter. Use the buttons below to page your way through the different levels that the reductionist approach identifies in biology. We will actually be using these levels, starting with the smallest (atoms) and working our way to more and more complex systems (molecules, cells, tissues, organ systems, organisms) until we conclude with the study of ecology.

  1. Make some preliminary observations and organize them
  2. Determine suitable research questions
  3. Frame a testable hypothesis
  4. Predict the outcome of the hypothesis
  5. Test the outcome of the hypothesis

Definitions of Life

Since biology is the science of life, we need to define living matter so that we can identify and distinguish it from non-living matter, which is usually the province of physicists, chemists, geologists, and astronomers. This isn't as easy as you might think. There is actually quite a controversy over where the boundaries of living vs. non-living should lie, when we look at viruses and viroids. If we decide that cellular organization is a requirement, then these organisms are not living organisms, since they don't organize their structure in cells. If we place more emphasis on replication of structures using energy, then viruses and viroids can certainly be said to reproduce and therefore be alive!

Even using the seven characteristics of your text, over a million species of living organisms have been identified, and many biologist think that millions more exist on earth (mostly as insects or plants in isolated areas). Finding a way to identify all the different manifestations of life on earth is not exactly straightforward or simple.

Here are some approaches to defining "living things"; each has its own advantages and limitations.

Which of these definitions is useful in determining whether the blob you found in the bottom of your glass of water is alive in the biological sense? Which help you understand how something that is alive will respond to its environment? to other organisms?