1. What ere the historical limitations of previous classification systems that led to and are solved by the three domain system that is in use today?
2. Why is the gene coding for ribosmal RNA(rRNA) used for establishing phylogenetic relationships and how does this compare to previous methods for placing organisms in appropriate taxa?
3. What are the factors that limit our ability to fully classify and understand microbial diversity and what implications do these challenges have for environmental and health management?

Each answer has to be a minimum of 125 words. I will also need references.