Electroreception is limited to aquatic environments because on here is the resistivity of the medium is low enough for electric currents to be generated as the result of electric fields of biological origin. In air, the resistivity of the environment is so high that electric fields from biological sources do not generate a significant electric current. Electroreceptor are found in a number of species of fish, and in at least one species of mammal, the Duck-Billed platypus.
A fold occurs when an originally flat or a plane surface of sedimentary rocks undergoes a bent or a curve and that may lead to permanent deformation.
And are formed due to the slumping of the sedimentary materials. They can form under the conditions of the compressional stress, hydrostatic pressure, and temperature gradient.
A set of folds is distributed at a region scale makes the fold belt and is commonly found in the orogenic zones or the mountain building areas. These folds are of various types as Anticlines, Synclines, and Antiforms.