Why is it important to set a control group in a scientific experiment, like in the pillbug experiment?

What is the control substance in this experiment?  

The outer wall of the esophagus is referred to as the: 

In which layer of the digestive tract would you find simple columnar epithelium cells? 

The outer wall of the esophagus is referred to as the: 

Trypsin, an enzyme produced by the pancreas, helps in breaking down _____________ into ______________. 

Lacteals absorb ________________ and are located in the_______________.

Trypsin, an enzyme produced by the pancreas, helps in breaking down _____________ into ______________. 

Muscular development, such as in competitive body building, is an example of:

Immediately after a large meal, one would expect: