The Saint Peter
Ornate Wrasse Peacock
Ponte de dogfish
General characteristics of Vertebrates
It is not for nothing that they are represented in the most "high" part of the tree phylogenetic fauna and flora!
Indeed, they are composed of many complex organs that work well together:
– A digestive tract : Two jaws, often differentiated teeth, a stomach, liver, pancreas, intestine and anus,
– The Respiratory organs Effective, lungs or gills,
– A Circulatory system With a Heart – atrium (s) and ventricle (s) – A dissolved oxygen distribution network and digested foods to consumer, vessel and capillary tissues;
– The Reproductive organs With well-differentiated sexes, male or female. (not counting the Ascidians).
– A Internal Central Frame Supple that serves as a tie to the muscles, it is composed of several hundred bones of which many are articulated and allow a rapid locomotion, the limbs. We guess, with the stacking of the vertebrae, the indices of a Métamérisation That we have encountered previously in other less evolved groups: in annelids worms and crustaceans, for example.
– and, let's not forget the "top": a highly developed central nervous system, protected in the solid cranial box and extended by the spinal cord well sheltered in the vertebral holes, behind the column of the same name.
– You will have noticed that the fish, which are the oldest vertebrates, have scales and that these scales are found in turtles and birds (paws). The same goes for their eggs. These characteristics do not exist in marine mammals, whales and dolphins.
The branching of vertebrates is not, as many think, the culmination of an evolution whose ultimate goal would be man, an anthropogenic evolution. Fish, first vertebrates, go back to early primary, like most invertebrate metazoan. Some scientists claim that Pikaïa – a fossil of the famous Burgess shales in Canada (RB053)-570 million years – would be the ancestor of vertebrates... What can be said without reservation is that the differentiation in several Classes (RB003) has gradually been made, during the various geological Eres, surviving all the large extinctions of mass (RB054) as is attested by the Fossils encountered around the world.
Mammals and birds are the most "recent" Classes. These are also the two most advanced Classes. These are Homeotherms : The temperature of their body is kept high. A "plus" that allows them an active life in conditions that can be difficult. But they must feed their "boiler" permanently!
Our beloved " Homo sapiens Only a few million years old, a trifle, the variety Subaquaticus is even newer: 1943, Cousteau-Gagnan, with their first regulator!
If the first vertebrates – the fish – lived exclusively in the water, their descendants gradually freed themselves from the major aquatic environment – innovation (RB056) of the fins ' replacement legs – to conquer the land surface. Some even ended up reigning in the air, the birds. Others have returned, very recently, to the marine environment such as whales, sea birds and some species of turtles without recovering the radiated fins of their ancestors.