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Characteristics of vertebrates


The animal world is very important on our planet, being ourselves part of that world. There are many ways to classify animal species, but the most accepted way is to differentiate between vertebrates and invertebrates. To know in depth the part of the animal world to which we belong, today in this lesson of a we will talk about the characteristics and classification of vertebrate animals .

Characteristics of vertebrate

Vertebrates are all those animals that do not belong to invertebrates , that is, those that have a backbone or spine . Vertebrates are animals with great adaptability, which over the centuries have managed to move from a freshwater habitat to terrestrial and marine habitats.

Vertebrates can vary their characteristics depending on the environment in which they live, but there are a number of common characteristics. Some of these features are as follows:

Vertebrate body structure

All vertebrates have 3 parts of the body:

  • Head
  • Trunk
  • Extremities or limbs

Organs of the vertebrate body


  • Nervous system . They have a central and peripheral nervous system . They also have muscles and skeleton that allow them to perform movements.
  • Circulatory system . They have a circulatory system composed of a heart and blood vessels.


  • Multi-layered epidermis : The epidermis differentiates into several superimposed cell layers. Within the vertebrates, the formation of the “skin” with several layers and associated structures such as scales, feathers, etc. occurs.


It has a skeleton , which can be bone or cartilaginous, which has an axial part, that is, the spine.


Vertebrate sexuality

In these type of animals there is sexual dimorphism. That is, males and females are distinguished. Its form of reproduction is also sexual although fertilization can be external or internal.

  • External fertilization ( Oviparous ). They are vertebrate animals that lay eggs. In other words, the offspring develop outside the mother’s body. For example: the chicken, ostrich, reptiles and many species of fish.
  • Internal fertilization ( Viviparous ). Fertilization is provided within the mother’s body. For example, mammals and a variety of fish.Examples of viviparous animals



The brain and the major sensory organs are protected by a capsule called the skull


Their breathing

Breathing can be gill or lung .

According to the aforementioned classification, two types of breathing can be indicated : through a pulmonary apparatus or through bronchial tubes.

  • Pulmonary. Reptiles possess lungs. Mammals, birds and amphibians in adult status too.
  • Branchial On the other hand, fish and amphibians in the larval state have gills.


Vertebrate body temperature

This temperature and its variation (or not) will depend on the subgroup to which the vertebrate belongs. Thus, it is divided into 2 large groups: those with hot blood and those with cold blood.

  • Hot blood. Mammals maintain an invariable body temperature type . Within this group are also birds.
  • Cold blood. Reptiles, for example, have a variable body temperature depending on the environment where they are found. For this reason (and together with amphibians) they are said to be cold- blooded animals . In the case of fish their body temperature is also variable. For this reason there are cold water and other tropical (warm) water fish.


Body sizes 

Vertebrates are significantly larger than invertebrates. Most invertebrates are only a few inches tall, very often the sizes are given in millimeters. Exceptions among the invertebrates are only the cephalopods , some crustaceans ( lobsters , lobsters ) and giant clams . Vertebrates of a few centimeters in size, on the other hand, always belong to the smallest species of their taxon .

The smallest aquatic vertebrates are some gobies (eg Schindleria brevipinguis ) and carp fish (eg Paedocypris progenetica with a length of 7.9 mm in the female and 10 mm in the male), the smallest terrestrial vertebrate of the frog Paedophryne amauensis ( with a length of 7.7 mm).  The Etruscan shrew ( Suncus etruscus ) having a body length of 2 cm and a weight of 1 g and Hummel bat ( Craseonycteris thonglongyai ) are having a weight of 1.5 to 3 g as the smallest mammals.

The largest vertebrate is the blue whale ( Balaenoptera musculus ) with a maximum length of 30 meters and a maximum weight of 200 tons. The largest recent terrestrial vertebrate is the African steppe elephant ( Loxodonta africana ) with a maximum weight of 7 tons. The largest extinct vertebrates of the mainland were the sauropods (Sauropoda), a very diverse group of dinosaurs.

Prerequisites for this increase in size of the vertebrates were their unique, consisting of bone and cartilage inner skeleton , the development of a very powerful muscles and the closed cardiovascular system .

Bilateral symmetry

When the animal can be divided into two equal halves only by one plane. Animals with bilateral symmetry are more complex and show a greater degree of cephalization (greater development of the nervous system and sense organs).

In animals with this symmetry, a right and a left part, a dorsal and a ventral surface are distinguished; an anterior or cephalic limb and a posterior or caudal limb.

The active movement implies a bilateral symmetry of the animals’ body, which is distinguished by elongated shapes. One of the ends of the elongated body, the first that comes into contact with the explored terrain, constitutes the head that tends to be differentiated. In the head the main organs of the senses, the nerve centers and the organs responsible for the capture of food are concentrated; waste products from the feed are expelled by the opposite end of the body.

These characteristics are usually contrary in animals that live fixed to a substrate, which have radial symmetry and undifferentiated head, that is, that the animals have a symmetry or arrangement of body parts in relation to an axis or plane.


Classification of vertebrate animals

To continue with this lesson on the characteristics and classification of vertebrate animals, we must talk about the different classes into which vertebrates are divided.


Mammals are the best known vertebrate class. They are characterized by being warm-blooded, possessing mammary glands thanks to which they can produce milk, and by being viviparous, with the exception of monotremes that are oviparous.

More than 5000 different species of mammals are known, of which 5 belong to monotremes, 272 to marsupials and the rest to placentals. Placentals are those mammals whose offspring are retained in the mother’s womb to be fed by a placenta. Placentals are the most extensive subclass of mammals, being divided into  16 orders.



The birds are warm-blooded vertebrates whose hind limbs only serve to walk, jump or stay on the ground, while the former are wings, which allow them to fly. They have a body full of feathers and a beak without teeth, and their reproduction is oviparous.

One of the most relevant characteristics of birds is their migration process . Due to the climatic difference of both hemispheres many birds migrate, although these migrations can also be due to the search for food or the availability of a habitat.


Fish are aquatic vertebrates that inhabit oceans and rivers around the world. They are characterized by being ectothermic , being able to regulate their temperature through the habitat, by their gill breathing, and have a body full of scales and with swimming fins.



Reptiles are vertebrates characterized by cold-blooded animals , having skin full of scales, and their origin millions of years ago. Reptiles cannot control their body heat, they are oviparous and usually populate warm climates.



Amphibians are very special vertebrates, since they are capable of undergoing a transformation during their development, a kind of metamorphosis. Among its characteristics are not being able to control your body heat and having a gill breath during your larval phase and a lung breath in your adult phase.

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