1. How is both the external and internal stimuli involved in doing this:

Question

You are hungry so you reach for an apple in a fruit bowl.

2. Why is a hypothesis important to controlled experiments?

Is it becasue you are trying to explain the effect that it would have to a substance if it is challenged to a difference in it's regularity?

Answer 1

Internal stimuli is when you feel something like, hunger, pain, sleepy, etc.
External stimuli is usually what you do in response to the internal stimuli. Ex. You fell and now your head is pounding (internal stimuli), so you go take some medicine (external stimuli). So in the case of the apple, You are hungry (internal), so you reach for an apple in a fruit bowl(external).

A hypothesis is important to a controlled experiment because, it states only one change in the experiment, if there were more than one change, it would not be a controlled experiment.