Vertebrates are animals that have a spine and a skull. Hagfish, lampreys, fish, amphibians, reptiles, birds and mammals are some groups of vertebrates.

The sloth is a vertebrate of the mammalian group.
Vertebrates are animals that have a spine and a skull. They are extremely diverse beings, varying in size, form of feeding, habitat and type of reproduction. Although invertebrates are more numerous than vertebrates, these are undoubtedly the most remembered when we talk about animals.

All vertebrate animals can be classified into three groups: Myxiniformes, Petromyzontiformes and Gnathostomata. In the first group, there are the so-called hagfish or sorceresses. In the Petromyzontiformes group, there are animals popularly known as lampreys. Finally, in the Gnathostomata group, there are fish, amphibians, reptiles, birds and mammals.

Summary about vertebrates

  • Vertebrates are chordate animals that have a spine and a skull.
  • Chordates share four basic features: the presence of a notochord, hollow dorsal nerve cord, pharyngeal slits, and postal muscular tail.
  • All vertebrates can be classified into three groups:
    • hagfish are part of the Myxiniformes group;
    • lampreys are part of the Petromyzontiformes group;
    • fish, amphibians, reptiles, birds and mammals are part of the Gnathostomata group.
  • Invertebrate animals differ from vertebrates in that they do not have a vertebral column and a skull.

Chordates and the relationship with vertebrates

To better understand what vertebrates are, we must first know the phylum chordates. Chordates (phylum Chordata) are animals that have bilateral symmetry and share four basic characteristics, which despite being observed in all chordates , in some species are present only during embryonic development.

  • notochord

The notochord is one of the most striking features when we talk about a chordate. It is characterized by being a flexible rod located between the digestive tube and the nerve cord. In vertebrates, the skeleton develops around the notochord , and the adult retains only traces of this embryonic structure.

  • hollow dorsal nerve cord

The hollow dorsal nerve cord, another characteristic present in a chordate, develops and gives rise to the central nervous system of these animals.

  • pharyngeal clefts

In all chordates, along the outer surface of the pharynx, arches separated by grooves are observed . In most chordates, grooves develop into slits, called pharyngeal clefts. The slits ensure that water enters the mouth and leaves the body without passing through the digestive tract.

In vertebrates, with the exception of tetrapods (four-limbed vertebrates), pharyngeal slits and arches form the gills. In tetrapods, the pharyngeal arches that surround the sulci form parts of the ear and other structures present in the neck and head region.

  • Post anal muscle tail

Finally, there is the muscular postcard tail, a tail that extends past the anus. In many species, it is greatly reduced during embryonic development .

What are vertebrates?

Vertebrates are animals that are part of the chordate group, and can be defined as chordate animals that have a spine and skull . Both the skull and the vertebral column are important structures for the protection of the vertebrate nervous system, which is very complex when compared to other animal groups.

All vertebrates can be classified into three categories:

  • In the Myxiniformes group are the animals known as witches, or hagfish, jawless vertebrates that have a skull formed by cartilage and highly reduced vertebrae.
  • In the group of Petromyzontiformes are the animals known as lampreys. Like hagfish, they stand out for being jawless vertebrates.
  • In the Gnathostomata group is the largest number of vertebrates, which stand out for having mandibles. Fish, amphibians, reptiles, birds and mammals are part of this group.

vertebrate groups

Let us know, below, some characteristics of the main categories of vertebrates.

  • agnatha

Agnatha are vertebrates that do not have a jaw.

 ▝ Hagfish

Hagfish do not have a jaw.

Hagfish are jawless vertebrates that are part of the Myxiniformes group. Along with lampreys, they form the Agnatha group. They have a skull formed by cartilage and reduced vertebrae .

They are marine animals and swim in a similar way to a snake . Most species are scavengers and feed on dead or diseased fish and worms. The mouth of these animals has tooth-like formations that are made of keratin.

 ▝ Lampreys

Most lampreys are parasitic.

Like hagfish, lampreys are animals that do not have a jaw. The skeleton of these animals is made up of cartilage . Most lamprey species are parasitic and feed by adhering their mouth and tongue to the surface of fish, drawing blood and tissue from their hosts. They can be found in both freshwater and saltwater environments.

  • gnathostomate

Gnathostomata are vertebrates that have a jaw.

 ▝ Pisces

Fish are animals adapted to live in an aquatic environment.

Fish are animals that live in an aquatic environment and stand out for being extremely diverse and adapted to life in water . Some characteristics observed in this group are gill breathing, presence of fins and hydrodynamic body . They are ectothermic animals, that is, they do not have the ability to maintain a constant body temperature using physiological mechanisms.

They can be classified into two major groups: chondritis and osteichthyes . Chondrocytes are the so-called cartilaginous fish, which have a skeleton composed predominantly of cartilage. Rays and sharks are cartilaginous fish. Osteichthyes, also known as bony fish, have an ossified endoskeleton. Catfish and carp are examples of bony fish.

 ▝ Amphibians

Amphibians are highly dependent on the aquatic environment.

Amphibians are animals whose most striking feature is the fact that some species have a double life, that is, an aquatic life stage and another terrestrial stage. They are ectothermic, and most of them live in humid habitats . These animals, in general, need to keep their skin moist, in order to ensure gas exchange with the environment ( cutaneous respiration).

Amphibians can be classified into three basic groups: Anura, Urodela and Gymnophiona. Toads, frogs and tree frogs are anuran amphibians. Salamanders are urodels. The caecilians belong to the Gymnophiona group, also known as Apoda.

 ▝ Reptiles

Turtles are reptiles that have a shell.

Reptiles are vertebrates that have definitively conquered the terrestrial environment evolutionarily. They are animals that have a thick epidermis with scales and/or osteoderms (bone deposits) that help prevent dehydration. In addition, most reptiles lay eggs, which have a thick shell that prevents the embryo from drying out.

Like amphibians and fish, reptiles are ectotherms. They can be classified into four groups: Testudines ( turtles , tortoises and tortoises), Crocodylia (crocodiles and alligators), Squamata (lizards and snakes) and Rhynchocephalia (tuatara).

 ▝ birds

Birds are animals that have a body full of feathers. Some of them have colorful plumage, which attracts the attention of animal traffickers.

Birds are vertebrates whose bodies are covered with feathers . Animals have adaptations to flight , such as the presence of wings, feathers, large pectoral muscles and the absence of a urinary bladder and teeth.

Despite being well known for their ability to fly, not all birds are able to fly , which is the case of the ostrich and the penguin. They are endothermic animals, that is, they regulate their body temperature using their own metabolism.

 ▝ Mammals

Platypuses are mammals that lay eggs.

Mammals are animals with fur and mammary glands on their body. The mammary glands produce milk , which is provided to the pup early in its development. Hair, in turn, is related to maintaining temperature. Mammals, like birds, are endothermic animals.

They can be classified into three groups: monotremes (chidnas and platypuses ) , marsupials ( kangaroos , koalas and skunks) and placentals (dogs, cats, horses , oxen, monkeys and humans).

Difference between vertebrates and invertebrates

Unlike vertebrate animals, invertebrate animals do not have a backbone or a skull . Due to this characteristic, many of its representatives have a soft body, as is the case of nematodes, cnidarians and molluscs . Like vertebrates, invertebrates show great variation in their diet, habitat, shape, size, and reproduction.

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