The Process of Science. Scientific Theories in Biology

Science helps human beings understand the natural world. Science aims to be objective rather than subjective even though it is very difficult to make objective observations and to come to objective conclusions because we are often influenced by our own particular prejudices. Still, scientists strive for objective observations and conclusions. We also keep in mind that scientific conclusions are subject to change whenever new findings so dictate. Quite often in science, new studies, which might utilize new techniques and equipment, tell us when previous conclusions need to be modified or changed entirely.

Scientific Theories in Biology. The ultimate goal of science is to understand the natural world in terms of scientific theories, concepts based on the conclusions of observations and experiments. In a movie, a detective might claim to have a theory about the crime, or you might say that you have a theory about the win-loss record of your favorite baseball team, but in science, the word theory is reserved for a conceptual scheme supported by a large number of observations and not yet found lacking. Some of the basic theories of biology are as follows:

Evolution is the unifying concept of biology because it pertains to various aspects of living things. For example, the theory of evolution enables scientists to understand the history of life, the variety of living things, and the anatomy, physiology, and development of organisms—even their behavior. Because the theory of evolution has been supported by so many observations and experiments for over a hundred years, some biologists refer to the principle of evolution. They believe this is the appropriate terminology for theories that are generally accepted as valid by an overwhelming number of scientists.

The Scientific Method Has Steps. Scientists, including biologists, employ an approach to gathering information that is known as the scientific method. The approach of individual scientists to their work is as varied as they themselves; still, for the sake of discussion, it is possible to speak of the scientific method as consisting of certain steps (Fig. 1.5).

Figure 1.5 Flow diagram for the scientific method. On the basis of observations and previous data, a scientist formulates a hypothesis. The hypothesis is tested by further observations or a controlled experiment, and new data either support or falsify the hypothesis. The return arrow indicates that a scientist often chooses to retest the same hypothesis or to test a related hypothesis. Conclusions from many different but related experiments may lead to the development of a scientific theory. For example, studies in biology of development, anatomy, and fossil remains all support the theory of evolution

After making initial observations, a scientist will most likely study any previous data, which are facts pertinent to the matter at hand. Imagination and creative thinking also help a scientist formulate a hypothesis that becomes the basis for more observation and/or experimentation. The new data help a scientist come to a conclusion that either supports or does not support the hypothesis. Because hypotheses are always subject to modification, they can never be proven true; however, they can be proven untrue—that is, hypotheses are falsifiable. When the hypothesis is not supported by the data, it must be rejected; therefore, some think of the body of science as what is left after alternative hypotheses have been rejected.

The Discovery of Lyme Disease. In order to examine the scientific method in more detail, we will relate how scientists discovered the cause of Lyme disease, a debilitating illness that affects the whole body.

Observation. When Allen C. Steere began his work on Lyme disease in 1975, a number of adults and children in the city of Lyme, Connecticut, had been diagnosed as having rheumatoid arthritis. Steere knew that children rarely get rheumatoid arthritis, so this made him suspicious and he began to make observations. He found that (1) most victims lived in heavily wooded areas, (2) the disease was not contagious—that is, whole groups of people did not come down with Lyme disease, (3) symptoms first appeared in the summer, and (4) several victims remembered a strange bull's-eye rash occurring several weeks before the onset of symptoms.

Hypothesis. Inductive reasoning occurs when you generalize from assorted facts. Steere used inductive reasoning; that is, he put the pieces together to formulate the hypothesis that Lyme disease was caused by a pathogen most likely transmitted by the bite of an insect or a tick (Fig. 1.6).

Figure 1.6. Flow diagram for Lyme disease study

Deductive reasoning helps scientists decide what further observations and experimentations they will make to test the hypothesis. Deductive reasoning utilizes an "if . . . then" statement: If Lyme disease is caused by the bite of a tick, then it should be possible to show that a tick carries the pathogen and that the pathogen is in the blood of those who have the disease. However, when Steere tested the blood of Lyme disease victims for the presence of infectious microbes, not a single test was positive. Finally, in 1977, one victim saved the tick that bit him, and it was identified as Ixodes dammini, the deer tick. Then Willy Burgdorfer, an authority on tick-borne diseases, was able to isolate a spirochete (spiral bacterium) from deer ticks, and he also found this microbe in the blood of Lyme disease victims. The new spirochete was named Borrelia burgdorferi, after Burgdorfer.

Conclusion. The new data collected when Burgdorfer applied deductive reasoning supported the hypothesis and allowed scientists to conclude that Lyme disease is caused by the bacterium Borrelia burgdorferi transmitted by the bite of the deer tick.

Reporting the Findings. It is customary to report findings in a scientific journal so that the design and the results of the experiment are available to all. For example, data about tick-borne diseases are often reported in the journal Clinical Microbiology Review. It is necessary to give other researchers details on how experiments were conducted because results must be repeatable; that is, other scientists using the same procedures must get the same results. Otherwise, the hypothesis is no longer supported.

Often authors of a report suggest what other types of experiments might clarify or broaden the understanding of the matter under study. People reading the report may think of other experiments to do, also. In our example, the bull's-eye rash was later found to be due to the Lyme disease spirochete.