Bacteria, archaea, fungi, algae
<u>Answer</u>: Weber's/Weber-Fechner's law of just noticeable difference
This phychologoical law is used to quantify the perception of change for a given stimulus. The perceived change is proportional/constant ratio to the initial stimulus. Thus, it is the minimum amount of a stimulus intensity change that will produce noticeable variation in sensory experience.
As in the example, it has been shown that this law is not function very well for extremes of stimulation.
The hypothesis would be: Consumption of a single apple every day will reduce the number of visits to the doctor.
The hypothesis is a proposed explanation that is a starting point for further investigations. So, in this case, we assume that eating one apple a day will keep us healthy, without the need for the doctor.