the areas of the sea.
the enormous mass of the marine waters, is a medium in which there are very variable conditions and determine the existence of one type or another of life.
the bottom, in which the areas receive enough light is covered with vegetation, serves as a substrate for the benthonic fauna. part of it resides on its same surface, as for example, is the case of lobsters or octopi and another is buried inside, as many worms do.
The area of free waters is called pelagic, and it is possible to distinguish two large areas: the neritic one, with shallow waters close to the coasts, and the oceanic, which is what is commonly known as the high seas. shallow waters is formed by plant plankton, which floats freely, and the numerous species of algae and some phanerogams that lay their roots on the rocks and the shallow bottoms of the coast. in this zone, the fauna reaches a great diversity, exploiting all the possible forms and configurations apt to survive. there are times that they are buried in the sand and their body takes the form of a sheet, with the eyes arranged in the upper part as is the case with flounders, sole or monkfish. others, for example, moray eels, acquire aspects of snakes so they can be introduced between the cracks in the rocks. the fish of the corals, in disc form, are able to move very quickly from one point to another, although unable to swim long distances at a constant speed. however, its brilliant coloring and that ability to jump out of reach of the enemy is the necessary quality to survive among the coral banks. These same plant-like, are actually invertebrates of colors and shapes more like a vegetable.
on the high seas, on the contrary, the environment imposes different conditions. the non-existence of an attainable fund prevents the development of the varied forms found on the coast. among fish, the typical form is general in all pellasgic representatives, with the back darker than the belly. They are gifted, in addition to good swimming abilities. the florase reduces the plant plankton and the occasional types of floating algae such as, for example, sargasso. In all cases, as with the animal plankton, the existence of flotation elements is necessary, be it grease droplets, gas bubbles or at least large surfaces that prevent a rapid fall to the depths. Many Platonic organisms also have swimming elements such as cilia, flagella or series of eyelashes, with which they are able to make small displacements.
if we ignore the big jellyfish, which are actually microscope components of the plankton, and the squids and nautiluses, which show a different form, the rest of the pelagic inhabitants of the oceans, both fish and mammals, have a similar appearance . this is a consequence of the molding action of the waters, in which a hydrodynamic form allows to offer the minimum resistance to the advance, with the consequent saving of energy.
next to this horizontal zonation of the marine waters there is the vertical, in which a first division, of great importance for life, allows us to distinguish between the euphotic and abyssal zones, or afotica. the first one covers from the surface up to about 200m deep, which often coincides with the continental shelf. The main characteristic of the area is the presence of light, in decreasing quantities as we go down, which allows the existence of plant life.
