<span>Some of the things that would make the experiment invalid would be, if there was a variation in the behavior of the class with respect to food - for example, if some people ate their breakfast earlier than the others. This then would mean that some students would have already digested their breakfast during the morning classes and the others would still be digesting. </span>
They leave their stoma closed during the day and opened during the night. Hope this helps.
No, not really because if nothing is near them they cant sense any type of danger. But if something is close they may be afraid but don't sense danger. It basically a spiderman myth.
Hope I helped!
- LILBLAKEYOUT