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 .
Eubacteria The domain that comprises the single kingdom Bacteria, containing the true bacteria. There are 11 main groups: purple (photosynthetic), Gram-positive, cyanobacteria, green non-sulphur, spirochaetes, flavobacteria, green sulphur, Planctomyces, Chlamydiales, Deinococci, and Thermatogales.ubacteria A kingdom (or subkingdom) of prokaryotic organisms that comprise present-day bacteria. They include aerobic and anaerobic species and occur in virtually all habitats. Some live in or on the bodies of other organisms, and may cause disease.