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Problem : What characteristics distinguish archaebacteria from eubacteria?

The cell walls of eubacteria are made of peptidoglycan, while archaebacterial cell walls can be composed of several diffferent compounds. Also, archaebacteria tend to live in much harsher environments than eubacteria.

Problem : How closely related are archae- and eubacteria?

The two Moneran groups are no more closely related to each other than each is to the eukaryotes.

Problem : What characteristic unifies archae- and eubacteria in the Kingdom Monera?

The archae- and eubacteria are prokaryotes.

Problem : By what characteristic are archaebacteria classified? What are the four types of archaebacteria?

They are classified according to the environments in which they live. The four types are methanogens, thermoacidophiles, sulfur reducers, and halophiles.