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 are often classified according to the manner in which they gain energy. Photoautotrophic Eubacteria manufacture their own energy through photosynthesis. Cyanobacteria, often called blue-green algae, are common photoautotrophic Eubacteria that are found in ponds and wetlands.