An Online Introduction to the Biology of Animals and Plants





Key Concepts




Section 1

Chapter 3

Development of Science Methods  









We accept today that science follows certain rules and processes that make it a dependable source of information, but those rules have not always been in place.  Until as recently as the 1700's, for instance, it was widely believed that living things could arise spontaneously from non-living, dead, or waste materials (this is called spontaneous generation), because people saw such materials "generate" living things like mold, or maggots.   In 1688, Italian naturalist Francisco Redi set out to test the idea with decaying meat in two containers:  one open to the air, the other sealed.  The open container meat eventually became infested with maggots.  And when critics insisted that it was simply that sealing the second container kept spontaneous generation from occurring, Redi did the test with an open container and one covered with cheesecloth, through which air could circulate (he suspected what we now know, that flies were the actual source of the maggots, but there is no record of whether he tested that idea), and the cheesecloth-covered sample produced no maggots.  However, even after many aspects of spontaneous generation were tested and became recognized as wrong, the basic concept persisted:  when germs were first discovered it was thought that they were a spontaneous product of sick tissues, rather than independent-living organisms that reproduced in the body.

It was a long road from that basic test by Redi to today's scientific method, but some of the approach he used persists:  modern science is about testing suspected explanations of ones observations. Observations can be made directly through ones own personal senses, or indirectly through instruments or second-hand from someone elses direct observations.  An explanation for one or more observations is properly called a hypothesis.  A hypothesis should produce testable predictions or it isn't much use scientifically, and the tests are most reliably done under controlled conditions.  The whole system is like puzzle-solving, in that you have to notice things, decide if what you're noticing is important, come up with explanations for those things, and test those explanations.  A good imagination is really valuable in doing science.

In biology
, complete control over conditions is hard to achieve, but scientists still strive for it.  If no alternative exists, testing may be done in the field, with well-planned and organized series of observations that look for evidence for the hypothesis predictions.  Controlled experiments may be done in a laboratory environment with different test groups, similar to how Redi did his experiment.  One group, the experimental group, is specifically set up to test some critical aspect (called the variable, sometimes the independent variable) of the hypothesis;  another group, the control group, duplicates the experimental group but removes the variable (or, if that isn't possible, changes it in some significant way).  In Redis second test, the experimental group was the cloth-covered containers (the cloth barrier as a test of air access but fly blockage was the variable), with the control test being containers with no cloth over them.   Control tests may also be run to try to figure out how outside influences (Confounding factors, discussed below) may be affecting an experiment. 

usually in some sort of number form (quantitative data, as oppose to non-number qualitative data) are collected from each group and compared.  The comparison is absolutely critical - just running an experimental group is possible (we could give a new headache remedy to a group of 100 people with headaches and record how much their headaches improved), but how would you know whether your results were directly connected to your variable - how many headaches would have improved on their own, or improved just because the subjects were given a pill and the expected to feel better (improvement based solely on expectations is called the placebo effect, placebo being an "empty" treatment)?  In a proper experiment, a control group would have been treated identically, given pills with the remedy ingredient removed;  the difference in effects in the two groups could then be said to be an effect of the remedy itself.

Aspects of your results that appear not from the variable, but rather from the process of experimenting itself - the act of treating can produce a placebo effect, for example - are called artifacts.  Parts of the experimental procedure that produce artifacts are one type of confounding factor.







200 people with headaches will be gathered in a comfortable setting.  The basics of the tests will be explained to them, including that they may be receiving a placebo treatment.  Each person will rate, on a scale of 0 (no headache) to 10 (the worst headache theyve ever had), the severity of their headache when given the treatment.  After one hour, they will be asked to rate their headache again;  the change for each individual will be added to the others in their group and averaged, and that average change will be compared between the groups.  Our prediction is that the experimental group average will be a larger negative number than the control groups.  The numbers are changes in headache strength  from the beginning to the end of that first hour.

    Experimental Group Average Change:  -4.15
                              Control Group Average Change:     ???

The Control Group change is -4.00?  or +2.2?   or -1.33?

A conclusion is made based upon your results.  You may have strong evidence for your hypothesis, weak evidence, or evidence that your hypothesis is mistaken (this condition is often called the null hypothesis).  A good scientist avoids saying that things are proved, because there may always be another and better explanation than yours that might produce the same results.  The history of science is a long series of new explanations for old results.






Modern science is based upon a descendant of that original scientific method, with some additions and minor changes.  A good experiment should be clearly designed and stated, and reproducible, so that someone else running the same test will get approximately the same results.  Research also generally is subject to peer review, scrutiny by others in the same field, usually when results are being published (in peer-reviewed journals) but sometimes at other stages of the process.  Peer review can be a double-edged sword:  on the one hand, it should help to assure that research is being properly done and conclusions make sense, but on the other hand, established scientists can be resistant to truly innovative ideas and approaches.

Modern biology, including medical research, can be confusing for a number of reasons, especially for the general public.  Often different studies seem to be completely at odds with one another, when in reality they were not looking at the same thing, or the results were misinterpreted by the media.  How data is collected can affect results (how would the headache study above be influenced if the rating system went from "1 = barely there, to 10 = the worst headache you could imagine"?), and experiments with living organisms are affected by a wide range of confounding factors, things that might be influencing the results.  One of the most  common confounding factors is pure chance -  if the mice you've picked to test happen to be particularly prone to cancer, anything you test will look cancerous - which requires that, whenever possible, test groups must be of sufficiently large size, or tests should be repeated many times.  If you use 100 mice, one cancer-prone mouse will not significantly change your results;  if that one mouse were in a group of five, the risks will look much greater.  Conclusions based on a single instance or a very limited group are said to be based upon anecdotal evidence and are not considered to be reliable.  You know the basic logic here as a part of life:  just because you were lucky enough to get away with something once doesn't mean you'll always be able to get away with it.  Good science can't be based on lucky happenings.

, if a test subject knew they were receiving a placebo, that would influence their responses;  this is why they are not told, producing what is called a blind test.  It was determined decades ago, however, that if the people giving out the treatments themselves knew which were real and which were placebos, they tended to treat the patients differently, sending subtle messages that could alter patient responses and results.  To eliminate those confounding factors, modern drug tests are double-blind:  those giving the treatments deal with numbered samples packaged and recorded elsewhere, not knowing which are real and which are not - there's no way they can alert the patients if they don't know which dose is which.  There is even talk of going to triple-blind testing, where the statisticians who work with the data don't know which group is which.

A researcher tries to recognize potential confounding factors while designing an experiment, and either eliminate them or set up separate control tests to determine their influence, but they are limited to what they can think of.  Often peer review will reveal a possible confounding factor never recognized, and it's back to running the test again.






Additional Information Links



A discussion about making qualitative data - ancient texts - quantitative for comparison purposes.

A fairly bizarre page on research done with marshmallow peeps that sort of follows scientific method but uses groups that are too small to eliminate chance as a confounding factor.  The peeps haven't protested.

A lab exercise on scientific method.

Why is the placebo effect stronger now than it used to be?

An interesting perspective piece on science and values.

Several views of ideas that persisted long after being scientifically shown to be false.






Click on term to go to it in the text.
Terms are in the order they appear.



Spontaneous generation
Francisco Redi
Scientific method
Field tests
Controlled experiments
Experimental group
Control group
Quantitative vs qualitative data
Placebo effect 
Peer review
Confounding factors
Chance, Role of
Test Group - Need for Numbers / Size

Anecdotal Evidence

Blind & Double-blind tests












Online Introduction to the Biology of Animals and Plants.

Copyright 2001-2017, Michael McDarbyContact.

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