Biology - Lesson 5

Hypothesis Testing involves two key steps:

1. Stating the hypothesis as clearly as possible and listing the predictions it makes

2. Designing an observational or experimental test for the validity of those predictions.

Prediction – Something that can be measured and that must be correct if a hypothesis is valid.

The predictions are the pegs upon which a hypothesis is hung. The predictions must be sound for the hypothesis to hold weight. When this doesn't happen, when predictions do not prove accurate, then more testing must be done to clarify and confirm the results and/or the hypothesis must be modified or completely revised.

The example the text gives for the necessity of hypothesis testing is the prior hypothesis for why giraffes have long necks. For decades, scientists have accepted the validity of the hypothesis that giraffes' long necks developed as an adaptation to living where there are abundant food sources in high locations. With long necks, giraffes can eat from high locations in the trees. However, more recently, scientists have discovered that giraffes use their long necks for a different purpose. When competing with each other during mating seasons, male giraffes use their necks to beat each other up, slamming each other with their necks by swinging their long necks at each other. The longer their necks are the harder they can swing at their opponent. Oftentimes, giraffes are injured (even seriously) during these fights where giraffes have been known to knock their opponent unconscious or even kill them. This wasn't at all taken into account by the original hypothesis about why giraffes have long necks. The original hypothesis therefore needed to be revised to reflect this new data. Scientists are now hypothesizing that competition among males may constitute part of the reason for the development of long necks and that they may also use their long necks for feeding in high places during droughts so that their long necks contribute to the fitness of individual giraffes in more than one way.

The other example given in this section is the hypothesis as to why chili peppers are hot. Connected to this hypothesis is the proposal that natural selection should favor fruits that taste bad to animal species that would destroy the seed if they ate it and should taste good to animal species that wouldn't destroy the seed but would disperse it after eating it. This is the directed dispersal hypothesis.

Further definitions from this section:

Null hypothesis – what we should observe if the hypothesis being tested doesn't prove accurate.