Why do we use a dichotomous key and how does it work?

Actinobacteria sp. are fermenting organisms (which do you use oxygen to breathe) referred to as chemoorganohetereotrophs this means they break down organic material and convert it to inorganic material. which part of the carbon cycle does this describe

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

Hershey and chase confirmed that dna, not protein, was the genetic material. how do the results of their two experiments support this conclusion?