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Science as a way of knowing
∗
David Rintoul
Robert Bear
This work is produced by OpenStax-CNX and licensed under the
Creative Commons Attribution License 4.0†
Abstract
The scientic method as it applies to biology
1 Science as a way of knowing
We absolutely must leave room for doubt or there is no progress and no learning. There is no
learning without having to pose a question. And a question requires doubt. People search for
certainty. But there is no certainty.
physicist Richard Feynman, in a lecture at the Galileo Symposium, 1964.
2 Introduction
What is Science?
thought about it?
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Everyone probably has some idea of what the word means, but have you ever really
If so, here are some questions to consider.
Is science a body of knowledge?
Is it the same thing as truth?
Is it a way to understand everything, or just a few things?
Is it a process, and if so, can everyone do it? Or do you have to be highly intelligent, highly trained,
or both, if you want to understand science?
Hopefully by the end of this course, or even by the end of this rst module, you will have some good answers
to those questions, and will be well on your way to thinking like a scientist (at least for this class!). Let's
start with the title of this chapter Science as a Way of Knowing.
That description is from the title of
a great little book by biologist John A. Moore, and is actually a pretty good answer to the question of
What is Science? Science is both a body of knowledge, and an evidence-based process for generating that
knowledge. The word itself comes from a Latin term,
scientia,
which means knowledge. But science is also
about a particular kind of knowledge - knowledge about the natural world. In addition, the process of doing
science can only help us gain additional understanding about the natural world. It is of no use to us if we
want to understand the supernatural. For that we need other ways of knowing.
There are also some other aspects of science which you need to know, as you move toward a better
understanding of both the scientic knowledge base and the scientic process.
Science
∗ Version
1.10: Feb 9, 2015 3:35 pm -0600
† http://creativecommons.org/licenses/by/4.0/
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requires interaction with the natural world in terms of observation, detection, or measurement.
is objective, or evidence-based; that evidence, or a repeated demonstration of the evidence, must be
available to everyone. Scientists generally don't just take your word for it.
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requires independent evaluation and replication by others.
leads to conclusions that are always
provisional, i.e., they will be rejected or modied if new observations
or measurements show that they are false.
There are, of course, other "ways of knowing". How do we know what we know? People who study knowledge
(yes, there are such people, and they are in the branch of philosophy known as epistemology) often classify
that knowledge based on the source of the knowledge. In mathematics and logic, for example, we can point
to things that we know are "rationally true".
In science, we focus on things that are "empirically true",
i.e., based on evidence that we can see, hear, touch, etc. In religion, and, to a lesser extent, in history, we
focus on "revelational truth", or knowledge that comes from another source that we accept as true, based
on our assessment of the reliability of the source. So the subjects that you might study at this university
can depend on dierent sources for the knowledge that you will be gaining. In this class we will focus, as
noted above, on objective evidence obtained from observations of the natural world, and we will use some
very specic terms to describe how those empirical observations form the basis for scientic knowledge and
understanding.
3 The process of science
So how does this process work? The processes that generate scientic knowledge are known as the
method.
scientic
But even as you learn this method, it is important to realize that this is not a set recipe or
process that MUST be followed in all cases. The scientic method is best understood as a statement of the
core logical principles underlying how science works. The process of science always uses these core logical
principles, but any individual scientic enterprise might not adhere exactly to the method outlined below
(Figure 1).
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Figure 1: The Scientic Method 1) Observations are used to formulate the 2) hypothesis, which
is then 3) tested with experiments or new observations. The 4) new data contribute to the pool of
observations, and also are used to rene the hypothesis as needed. Eventually the accumulated data
allow one to make a 5) conclusion, which can contribute support for an existing 6) theory, or in some
cases, support for a new theory. In all cases theories can be used to generate new testable hypotheses,
which is why we say theories are both explanatory and predictive.
All science starts with an
observation, or set of observations, about the natural world.
You might observe
a pair of male elk ghting in a high-country meadow in Colorado, for example. The next step, if you want to
think about this scientically, is to formulate some
hypothesis to explain that observation.
A hypothesis
is a statement that is simply an educated guess about the cause(s) of the observed phenomenon. In order
for that hypothesis to be useful in a scientic sense, however, it must have some additional characters. A
scientic hypothesis must be
testable, and it must be falsiable.
It does no good to generate a hypothesis
that you cannot test in the real world. Thus it would not be a scientic hypothesis if you stated that the
elk were ghting because invisible men in an invisible spaceship parked on the far side of the moon were
controlling these elk with undetectable brain waves. That might be the actual explanation, but you can't
test it, and you can't falsify it.
A good scientic hypothesis lends itself to making testable
predictions; if the hypothesis is true, then
X must be true. In this case you might state generate this hypothesis these are male elk, and they are
ghting for control of a herd of female elk. Immediately some predictions come to mind. If this hypothesis is
true, you should be able to detect that these are male elk. Without getting too close, you can see that they
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have antlers, and previous work by other scientists (part of the set of accumulated observations that you are
relying on) has shown that only male elk have antlers. Prediction conrmed. Another prediction might be
that there should be one or more female elk nearby, and that these females would eventually go with the
male who wins the ght or drives o the other male. You look around, and you see a herd of 10 or so female
(antlerless) elk watching the spectacle. Another prediction conrmed. You will have to wait until the ght
is over before you know if the prediction about the females staying with the winner is conrmed. But you
have two predictions conrmed, and so far your hypothesis is supported by the evidence. More importantly,
it has not been
falsied.
All of the data so far support it.
This brings up another important aspect of the process of science. In this case you made predictions and
conrmed them with additional observations. You didn't do anything to the subjects; you merely observed
them more closely. That is a valid approach. An equally valid approach would be to test your hypothesis by
means of
experiments.
Experiments are manipulations of the experimental system, followed by additional
observations. In this case, for example, you might hypothesize that the male hormone testosterone is causing
the elk to ght.
One prediction from that hypothesis would be that injection of testosterone into female
elk (which don't normally produce testosterone) would lead to aggressive behaviors in the female elk. You
would also predict that male elk, deprived of testosterone, would be less aggressive. You might be able to
come up with some other predictions from this hypothesis that could be tested with other experiments. You
would have to capture some elk (male and female) to do the experiments needed to test these predictions,
of course. That could be tricky, or dangerous, and you might need to hire and train help. Or you could
look for similar behaviors in smaller, more easily handled animals such as mice or rats, and do the same
experiments with those creatures. Both
of these approaches, using observations or using experiments, are
scientically valid, as long as your hypothesis is testable and falsiable. Furthermore, as you will learn many
times in this course, there are other aspects of the experimental approach, involving concepts like
size, variables, and controls, which you will need to consider as well.
sample
We'll save the discussion of those
until a bit later, after we conclude our consideration of the general scientic method.
If you look at (Figure 1), you will see that multiple tests of the predictions lead to an increase in the
number of observations. Any test of the hypothesis, no matter if it conrms or disconrms the hypothesis,
adds to our knowledge base. Generating new knowledge is one of the exciting parts of doing science, in fact.
All of these observations can be used by future generations of scientists to test future hypotheses.
You'll also nd another important word in (Figure 1), and that is the word
theory.
In regular con-
versations, people outside of science often use this word to mean an unproven or unsupported explanation,
a wild guess.
As you learned above, in science that description would be more appropriate for the word
hypothesis. In science, a theory means something quite dierent. Theory is used to describe a hypothesis,
or set of hypotheses, that is supported by substantial amounts of data from diverse lines of investigation. In
other words, it is NEVER a wild guess. There are many theories in science; examples relevant to the study
of biology include the germ theory, the cell theory, plate-tectonic theory, and of course the grand unifying
theory of evolution. All of them are well supported by incredible numbers of observations; all of them are
considered the best available explanation for a diverse set of observations.
In addition, as shown in (Figure 1), you can see that just as observations lead to
predictive hypotheses,
theories can lead to predictive hypotheses as well. In fact, one of the hallmarks of a theory is that it provides a
solid framework for generating hypotheses and making predictions. Scientists are condent in the explanatory
power of theories, and thus are comfortable in using them to construct hypotheses, design experiments, and
frame the interpretation of the data generated by those experiments. Just as a scientic hypothesis is useless
if it cannot generate predictive hypotheses, a theory must serve as a framework for hypothesis building
and testing. And just as the predictions of the hypothesis must be borne out by new observations if the
hypothesis is going to be accepted, predictions from a theory must be supported by the observations if the
theory is to continue to serve as the best available explanation for a vast set of observations.
Not shown in that gure, but implied nonetheless, is the fact that the observations must be repeatable.
Other scientists, working in other locations, need to be able to do similar experiments and get the same
results. That is what is meant by the statement that science is objective, not subjective. Another scientist
has to be able to get the same results as you, and vice versa. Again, the history of science has thousands of
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examples where a new and exciting result was announced, but eventually forgotten when other scientists could
not get the same result. Recent ones include the phenomenon known as cold fusion, or the identication
of a virus that was thought to cause Chronic Fatigue Syndrome (CFS). In all of these cases the original
observation was found to be awed in some way, and subsequent work, either by the original observers or by
others, revealed the aws and debunked the explanation.
Finally, it is important to remember that all scientic conclusions are provisional.
In other words, a
scientic conclusion is accepted as the current best explanation, but with the understanding that future
investigators could make observations that might negate or modify the conclusion. So it is likely that some
of the things that you will learn in this class are wrong, or at least incomplete. We still expect you to learn
them, since they are the current best explanation, but it is almost certain that something in this textbook,
or in the other materials for this course, will be shown by future scientists to be erroneous or incomplete.
Who knows, you might be the scientist who does the work that reveals the error. Scientists actually dream
about being the person who overturns a long-established notion, since that often means that their work
will be remembered, and may even appear in future biology textbooks. One example of overturning a longestablished concept, and ensuring a place in future textbooks, can be found in Louis Pasteur's experiments,
described below
4 Experiments and controls
As mentioned above, a common approach to generate new scientic knowledge is to perform experiments,
where the scientist changes the situation and then observes the eects of these changes.
In keeping with
the scientic method, this starts with an observation, from which the scientist generates a hypothesis. The
hypothesis leads to a testable prediction, followed by experiments based on that testable prediction. Let's
look at one of the most famous experiments in all of biology as an example.
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Figure 2: Pasteur's test of the hypothesis of spontaneous generation [By Carmel830 (Own
work) [Public domain], via Wikimedia Commons]. Pasteur attempted to explain the observation that
organisms (molds and bacteria) appeared in meat broth that had been boiled. His hypothesis was that
these organisms came from the air, rather than from spontaneous generation. That hypothesis would
predict that organisms would not appear if the meat broth was not exposed to air. He boiled the broth
in asks with long necks; air could not enter past the uid that was left in a U-shaped section of the
neck of the ask. As a control he boiled broth in other long-necked asks, but then broke the necks o
so that room air (and any microbes in that air) could fall on the broth. No organisms grew in the asks
with intact necks; organisms were found in abundance in the asks with the broken necks.
It was widely believed in ancient times that living things arose spontaneously if conditions were right.
One of the observations that led to this belief was that molds, bacteria, maggots and other life forms appeared
if one left a piece of meat out in the air for a while. This concept of spontaneous generation was tested in
1860 by Louis Pasteur, using an experimental setup diagrammed above (Figure 2).
Pasteur heated meat
broth, in glass asks, to a temperature where he imagined that no living things were left alive in the broth.
If he left this broth out in the open, it developed active bacterial and mold growth, an observation which was
consistent with the notion of spontaneous generation. But Pasteur, having recently learned about microbes,
suspected that the mold and bacteria arose not from spontaneous generation, but from microbes present in
the air. So he devised a set of experiments to test this hypothesis: Living microbial cells present on dust
particles in the air are the source of the living cells growing in the heated meat broth.
What prediction could one make with this hypothesis? You can probably think of a couple, but the one
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that Pasteur came up with was that if the meat broth was in a vessel which excluded cells dropping into it
from the air above, there would be no bacterial or mold growth in the broth. So he heated batches of broth
in long-necked glass asks until he thought the broth was sterilized, and also heated the necks of the ask
to allow him to bend them into an S shape. The ends of the asks remained open to the outside air, but
dust settled in the trap in the neck of the ask and did not reach the surface of the meat broth. In other
experiments, he broke o the neck after heating the asks, allowing dust particles to settle on the broth, or
waited a few days and then tilted the asks so that the broth came into contact with the dust trapped in the
bottom of the trap in the neck of the ask. Then he observed the results. Just as importantly, he repeated
the experiments several times to make sure that his observations were correct.
We've already discussed the hypothesis, and one prediction, above. But what are some other important
aspects of this experimental approach? One is the concept of a
variable.
A variable is some condition of the
experimental setup that can be manipulated by the experimenter. Ideally, the experimenter should change
only one variable at a time (keeping all other conditions identical); this makes interpretation of the results a
lot more straightforward. What was the variable in Pasteur's experimental setup? In this case, the variable
was access of dust to the surface of the broth. In asks that were left open, access was allowed. In the asks
that had an intact S-shaped trap in the neck, access was not allowed. Pasteur also manipulated this variable
by tilting the S-shaped asks so that accumulated dust could contact the broth.
The other important part of this experimental approach is the concept of
known by a shorter term as just
controls.
control experiments,
also
A control experiment is a setup where the variable is not
introduced, so that it can be directly compared to the experimental situation where the variable (access
of dust particles to the broth) is included.
So a control experiment for Pasteur's incubation of broth in
an open-necked ask would be incubation of broth in the S-necked asks. If the variable is introduced by
tilting the asks, the control would again be the S-necked asks. All other conditions (heating temperature,
amount of broth, size of asks, etc.) were the same in the experimental and control situations. The only
thing that was dierent was a single variable (access of dust particles to the meat broth), because that was
the hypothesized source of the living cells that grow in meat broth left out in the open. A single control
experiment is usually all that is needed if there is only a single experimental variable being manipulated.
But it is not always possible to simplify a system so that there is only one variable. In those cases, as you
will learn in the studio exercises for this class, you might need multiple control experiments. Experiments
and controls will also be repeated before the investigator reports the results. It will be described in a way
such that other investigators can readily repeat it as well. In some situations the results will be subjected to
statistical analysis, although this was not necessary in Pasteur's experiment. Statistical analysis is critical
in many scientic approaches, particularly in studies involving hypotheses about human subjects (e.g., the
hypothesis that smoking causes lung cancer), where experimental manipulation of the subjects is dicult
or impossible. A scientic experiment, no matter how the results are analyzed, should lead to a conclusion
that either supports, or fails to support, the hypothesis.
Finally, the experimental results should lead to
additional hypotheses, and additional predictions, that can generate further support (or lack of support) for
the hypothesis. Try to think of a few additional experiments that you might have suggested to Louis Pasteur
if you were alive in 1860, and if you could speak French!
5 Other aspects of science
The characteristics inherent in the scientic process lead to another property of science, and that is that
science is
self-correcting.
By that we mean that errors can be made, but that continued application
of the tools and processes of science will usually lead to elimination of the errors and a more accurate
understanding of the natural world.
Science never really and nally proves anything to be true; it can,
however, prove things to be untrue.
To some people, in fact, that characteristic of science, its uid and
changing nature, is maddening. If you require solid ground to stand on, and immutable truth in all aspects
of your life, you probably shouldn't become a scientist. If you nd excitement in being part of an enterprise
that is constantly changing the extent, and even the nature, of knowledge, then you have some of what it
takes to be a scientist. But even if you don't become a scientist, a bit on scientic knowledge, and a bit of
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practice with the scientic process, will help you understand the things you need to understand in order to
make intelligent decisions about many things, such as health care, climate change, or other concepts that
are in your future.
Science is also a curious mix of intuitive and counter-intuitive behaviors.
You practice the scientic
method intuitively every day, whether you realize it or not. If you ip on the light switch in your bathroom
in the morning, and the light doesn't come on, you probably take a scientic approach to solving that
problem. You might hypothesize that the bulb is burnt out, and if that hypothesis is correct, replacing the
bulb should solve the problem. So you do that experiment, and replace the bulb, and the light goes on, and
you can continue with your daily activities blissfully unaware of the fact that you acted scientically already
that day. Intuitive science in action!
But some aspects of science, and particularly the scientic process, are not intuitive. All of us have the
ability to think that our explanation of some phenomenon is correct, even if there are other observations that
contradict that explanation. In fact, we often search for additional evidence to conrm our conclusion, and
ignore any evidence that we might nd that casts doubt on the conclusion. This is known as
bias,
and is particularly strong in situations where we have an large emotional or nancial
conrmation
stake in the
conclusion. For example, you might consider yourself a pretty good basketball player. So when you have
missed 10 shots in a row, you keep shooting until you make a shot, and then you feel better about your belief
that you are a good basketball player, even if those shooting percentages contradict that belief. Or you might
make a visit to the chiropractor when your neck hurts, and the chiropractor might make your neck feel better.
But a few days later, when it hurts again, you might not take this as a sign that chiropractic manipulation
is not a cure. You might go back to that chiropractor, to have the same manipulation, because you have
already invested money there, and you'd like to think that you are not wasting your money. Conrmation
bias, of the active sort rather than the passive version in the previous examples, is particularly evident in
people who buy into conspiracy theories. They seek out others with the same beliefs, or they only look at
websites that are dedicated to that belief. It's only human nature that people like to hear what they think
they already know. As a character in Terry Pratchett's Discworld series observes, . . .what people think
they want is news, but what they really crave is olds. . .Not news but olds, telling people that what they
think they already know is true. We all like to think that we know everything that we need to know, and
scientists are no exception.
So scientists have to actively guard against conrmation bias. If a scientist has an hypothesis, she has to
come up with predictions and experiments that will
disprove that hypothesis.
If the experiments indicate
that the hypothesis is wrong, the scientist has to abandon that hypothesis and generate a new one, and it has
to include the results of those disconrming experiments. This is a very dicult assignment, and certainly
goes against lots of human impulses. As the physicist Richard Feynman wrote, you must not foolyourself, and you are the easiest person to fool.
The rst principle is that
Every good scientist has abandoned many
more hypotheses than he or she has conrmed; science teaches humility that way, for certain.
Scientists
must be able to change their minds if observations warrant it; there is no shame for a scientist who admits
being wrong. Exactly the opposite, in fact. There are many sad examples of individuals who hung on to
a hypothesis too long, and ended up with a tarnished reputation. But as we all know, admitting you are
wrong is dicult for most people, and scientists are human too.
6 The science of biology
It's now time to shift from a discussion of science in general to the specic scientic discipline that you will
be learning about, biology. Biology is the study of life. that naturally leads to the question What is life?
Suprisingly, that has proven to be a dicult question to answer in just a few words! Most textbook-level
denitions of life are merely a list of characteristics; anything that exhibits all of those characteristics is said
to be alive. Here's a typical list.
Living things:
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Respond to the environment.
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Assimilate and use energy from their environment.
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Reproduce (at the level of organisms) and can evolve (at the level of populations).
Maintain a relatively constant internal environment, even as the external environment changes (
ostasis).
home-
Are highly organized, relative to their environment.
These are general characteristics, and might describe all organisms, even those which have not yet been
discovered yet (e.g., those on other planets or solar systems).
Until those organisms are discovered and
studied, however, that statement is provisional. In addition, scientists have discovered that all living things
discovered to date (i.e., the ones on this planet).are composed of one or more cells, and have DNA as
their hereditary/genetic material. Some textbooks include these characteristics in their denition of life as
well. More importantly, the commonality of DNA as the genetic molecule in all known life forms is strong
evidence that all living things on this planet are related, i.e., they have a common ancestor.
A putative
common ancestor was a prediction made by Charles Darwin when he elucidated his theories about evolution
and natural selection. The fact that his prediction proved to be correct is one (of many) pieces of evidence
that support that theory. You'll learn about some of the other evidence later in this course.
One productive way to study and understand living things is to recognize that there is a biological
hierarchy, which is basically an organizational concept map that allows us to focus on various levels of life.
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Figure 3: The organization of life . Work by Eva Horne.
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This hierarchy (Figure 3)extends from atoms and molecules, through cells, tissues, organs, organ systems,
organisms, populations, communities, and ecosystems all the way to the biosphere (Planet Earth and the
living organisms populating it). Biologists often focus on one or another of these levels, simply because it
is far easier to study one level than to try to understand the entire spectrum, and the interactions between
those levels. But all biologists recognize that there ARE many interactions between these levels, and those
interactions lead to some very interesting and important processes as well.
Consideration of this hierarchy, coupled with the diculty in coming up with a simple denition of life,
leads some scientists to another perspective as well.
These scientists argue that it is pointless to try to
dene life. If life arose from self-replicating chemical systems, which is the working hypothesis in the eld
of science known as abiogenesis, and if there is a continuum running from atoms to molecules to cells, etc.,
then it is not possible to point to some arbitrary place on the continuum and dene it as living. Nobel
Prize-winning abiogenesis researcher Jack Szostak writes None of this matters, however, in terms of the
fundamental scientic questions concerning the transitions leading from chemistry to biology.
Indeed, as
you come to learn more about viruses in this course or elsewhere, you will probably have some sympathy
for this perspective. Are viruses alive? Or would it be better to say that they are somewhere along this
continuum, and bypass that question altogether?
As you proceed to learn biology in the studio classroom this semester, you will expand your understanding
of the details underlying those characteristics of living things. For example, in regard to organisms responding
to the environment, you will learn some of the ways that bacteria, plants and animals sense and respond to
environmental conditions. You will learn how bacteria, plants and animals reproduce, and how that process
of reproduction is integral to the process of evolution. You will learn about cells and tissues and organs, all
of which are highly structured and organized arrangements, and how energy is obtained and expended so
that these organized structures can be produced and maintained. Hopefully you will come to the realization
that life, in all of its diverse incarnations, is amazing. Which is why biologists continue to study it!
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