This suborder includes all multicellular animals. The set of cells can be organized into more or less complex tissues. The life of all individuals originates from a single cell, which by successive divisions gives rise to the remaining ones that will form the organism, then differentiating into the various tissues and forming the corresponding organs.
It is difficult to establish the origin of the Metazoans. It is admitted that the first animal organisms evolved to form the Protozoa, separating these into several branches, mainly that of the Flagellates and the Poriferos. From the common line, forms with added cells emerged that ended up constituting multicellular organisms. However, they did not form tissues so they remained at the level of Mesozoans. The next step was the organization of these cells in real tissues, appearing the Coelenterates . These animals are called diblastic because their body is made up of two unique cell layers, an outer (ectoderm) and an inner (endoderm). With the appearance of a third intermediate cell layer (mesoderm), the rest of the Metazoa appear, which are called triblastics.
In the embryonic development of triblastics, a simple digestive tube is first formed with two openings: a mouth and an anus. Later, to give the adult individual, in some this disposition is maintained, while in others the mouth appears in a different place. In this way, two main lines of Metazoans are distinguished: the Prostostomes (where the embryonic mouth, the blastópore, is still preserved in the adult) and Deuterostomes (the blastopore closes and the adult mouth appears in a different place).
A small list of species in Aragon would be the following:
images about the fauna in Aragon.|
photographs on invertebrates.
beneficial animals for agriculture.
Ebro | Landscape | Monegros | Moncayo | Ordesa
Zh2o | Photografies
Document | Nature in Aragon
The pasapues project is an extension of the Aragón project is like that, and tries to collect and relate all possible types of documentary information about Aragon: texts, books, articles, maps, illustrations, photographs, narrations, etc., and proceed to its publication and diffusion.
Metazoans. Invertebrates. Animal Kingdom. Fauna. Zoology, reproduction, physiology, metazoa, ecology, zoogeography, stone, earth, air
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