An entomologist is a zoolist interested in insects. The are interested in finding and studying the classification of the life cycle, insects environments, how they relate to humans and their organisims
Prokaryotic cells also have loose/free/a ring of DNA (not confined to a nucleus) and they can also sometimes have a capsule (slimy outer layer). Also they have slightly smaller ribosomes- 70s instead of 80s.
Because they supply much energy to the food by preparing their own food because the above one can't prepare it own their own