In experiments, scientists create artificial situations to test the hypotheses because they cannot make the necessary observations under normal conditions. Hypotheses are accepted for as long as they are supported by available evidence. This type of hypothesis is called as an alternative hypothesis.

Real marine biologists rarely have it as easy as our imaginary one, who was able to construct and then test his hypotheses about gills with just a few observations. Hypothesis testing reuires planned observations. The scientific process is a gradual one in which hypotheses are continually refined and modified, and new alternatives are produced, as more information becomes available.