Definition of a Tangent Plane We all have and intuitive idea of what the tangent plane to a point on a given surface should be. It is the plane that goes through that point and that it is tangent to the surface at that point. Suppose. z = f(x,y) is a smooth surface above the xy-plane (see the picture below).
The two prokaryotic domains (or empires),  Bacteria  (or  Eubacteria ) and  Archaea  (or  Archaeobacteria ), are subdivided into 35 phyla (or divisions): 30 phyla in the domain  Bacteria , and 5 phyla in the domain  Archaea .
Bacteria are classified in two different kingdoms Archaebacteria and Eubacteria The difference between Eubacteria and Archaebacteria is their cell walls and the lipids in their plasma membranes. in addition, the structure and function of the genes of Archaebacteria are more similar to eukaryotes than to eubacteria.