Introduction 19 



2. The formulation of hypotheses. During the initial gathering 

 of facts, certain trends may be observable. From these the investigators 

 formulate various suppositions or hypotheses which they believe sum- 

 marize the observed facts. Most of these early hypotheses will prove 

 untrue, but they are of value in directing further experimentation or 

 observation. 



3. The checking of the hypotheses. This represents a very im- 

 portant phase of the investigation, for the methods of science require 

 the continuous discarding of invalid generalizations and the formulating 

 of new. Experiments are devised which either validate or invalidate 

 the hypotheses. 



4. The formulation of a theory. When finally a hypothesis is 

 shown to be correct by thorough testing, a theory is formulated which 

 is in accord with the observed facts. 



5. The discovery of a scientific law. When the theory has been 

 tested by numerous other investigators in many different situations, a 

 scientific lazv is discovered. Even though the law may seem to be 

 entirely correct at the time of its formulation, the open-mindedness of 

 science is such that it requires changes in the law if new techniques or 

 additional facts are not in accord with it. 



6. The utilization of the scientific law. Once the law has been 

 established, it may be used to explain newly observed phenomena. 



The Scientific Experiment. — One of the most useful techniques 

 for accumulating facts and testing generalizations is the scientific ex- 

 periment (Fig. 1). Although there is infinite variety in scientific ex- 

 periments, all have certain characteristics in common. 



First of these is the fact that all conditions of the experiment are 

 constant with the exception of the variable under consideration. 



Second, a control group must be utilized. The control is treated 

 in exactly the same manner as the experimental group, but the variable 

 under investigation is kept constant. 



Finally, a sufficient number of experimental units must be used 

 to give statistically valid results. 



BIOLOGY AS A SCIENCE 



The application of the scientific method to many phases of human 

 activity has made possible the rise of the diverse sciences which we 

 recognize today. Many of these various sciences such as chemistry, 

 phvsics, mathematics, and engineering deal primarily with nonliving 



