Why eukaryotes need 3 rna polymerase?
Each of the 3 RNA polymerase in eukaryotes perform a different function. For example, RNA pol 2 is involved in mRNA synthesis, RNA pol 1 synthesizes most rRNAs and RNA pol 3 synthesizes tRNNA, the 5S rRNA and other small nuclear RNAS. Eukaryotes are more complex than prokaryotes, hence why eukaryotes would require more RNA polymerases.