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Vertebrates

Vertebrates are a large and very diverse group of animals, among which we can find birds, amphibians, mammals, fish and reptiles. As a characteristic of the group, and as their name indicates, they all have a backbone or vertebral column through which part of their nervous system runs, which is relatively complex. This characteristic of vertebrates has allowed them to adapt very efficiently to different environments (air, land and water), but also within these environments we can find vertebrates that live in inhospitable situations, such as sub-zero temperatures and great depths, to mention a few examples.

Another characteristic of vertebrates is that they are provided with a skull that protects the brain, and have either a cartilaginous or bony skeleton. There are many species that develop their entire life in the water, carrying out gaseous exchange through their gills, such as fish. Others have specialized organs (lungs) for gas exchange, and therefore those marine species with lungs will regularly need to come to the surface to breathe.

Currently there are approximately 69,000 different vertebrate species described, of which approximately 33,000 are fish, 11,700 are reptiles, 10,000 are birds, 8,000 are amphibians and 6,400 are mammals. Despite being a very numerous subphylum, vertebrates represent less than 5% of all currently known living species. In this diverse subphylum of species we find from species that do not exceed 1 cm in length, such as the small frog Paedophryne amauensis, to the largest living species on the planet, the blue whale (Balaenoptera musculus) whose records exceed 30 meters in length and up to 170 tons in weight.

Vertebrates reproduction is mostly sexual, through the production of haploid gametes and cross-fertilization. There are some exceptions of self-fertilization in certain species of fish (Cyprinodontidae family) and even a few species of reptiles that are able to reproduce without fertilization, through a process known as parthenogeneis.



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