Subphylum Vertebrata

Introduction

What is Subphylum Vertebrata?

Subphylum Vertebrata or simply Vertebrata is a subphylum of the phylum Chordata. The phylum Chordata is a classification of animals that have a notochord. In the subphylum Vertebrata, the notochord is replaced by vertebral columns. Hence, the name vertebrates. Vertebrata is classified under the category phylum Chordata because animals belonging to the subphylum Vertebrata had notochord at some point in their development. The subphylum Vertebrata is further classified into subdivisions Agnatha and Gnathostomata. Both Agnatha and Gnathostomata are further divided into more classes. On looking upon these terms, you might feel overwhelmed but rest assured. These terms have been explained to boost your understanding in the following article. Before we get further, we need to have a quick crash course of the taxonomic hierarchy.

What is a taxonomic hierarchy?

Taxonomic hierarchy is a system of organisation of animals. It classifies animals based on their similar characteristics and ranks them in increasing or decreasing order. The highest rank is the kingdom, and the lowest position is species. Here is the list of ranks in the taxonomic hierarchy in reducing demand.

• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species

As you can see, the second rank is of the species. In the animal kingdom, we talk about ten species, of which Chordata is one. And as mentioned already, the phylum Chordata can be divided into three further subphylums, of which Vertebrata is one.

Subphylum Vertebrata Classification

The classification of subphylum Vertebrata is based on the presence and absence of jaws. In other words, the division is based on animals that have jaws in their mouths and animals that are not supported by the jaws. Subphylum Vertebrata is divided into two; Agnatha and Gnathostomata. The animals belonging to the category of Agnatha do not have jaws in their mouths. On the other hand, the animals belonging to the Gnathostomata class have jaws in their mouths.

Agnatha

In Agnatha, the mouth is not supported by the jaws. The organisms belonging to this class are also called jawless vertebrates. In this group, the animals have a circular mouth that performs the function of sucking, also known as the suctorial funnel—for example, Petromyzon. Petromyzon is a jawless vertebrate that fits the animals belonging to Agnatha. Other important characteristics do not have paired appendages, limbs, or fins. The exoskeleton is also absent. Instead, the endoskeleton is made up of cartilages. Agnatha is further divided into a single class known as Cyclostomata. Myxine or Hagfish is the animal belonging to this class. The distinctive feature of this class is that they have oral tentacles in their mouth.

Gnathostomata

Animals supported by jaws in their mouths belong to the category of Gnathostomata. They can be divided into two superclasses; Pisces and Tetrapoda. Fishes belong to the superclass of Pisces and animals with legs or four limbs belong to the superclass of Tetrapoda. Pisces can be further divided into two major classes; Chondrichthyes and Osteichthyes. Fishes composed of cartilage belong to the class of Chondrichthyes and fishes collected of bones belong to the type of Osteichthyes. Tetrapoda are organisms that have four limbs or leg-like structures. They are classified into four classes; Amphibia, Reptilia, Aves, and Mammalia. The animals in this category are primarily terrestrial but live in water. For example, frogs belong to the class of amphibians and they can live in both land and water just like other amphibians. The classes of Tetrapoda are elaborated below –

• Amphibia has two pairs of limbs and can live in both land and water. For example, Salamander and Frogs
• Reptilia – The animals belonging to the reptilia class mostly live on land and are crawlers. Scales and limbs are present—scales in snakes and limbs in alligators and crocodiles
• Aves – Birds belong to this class. Aves have a bony endoskeleton, and they use feathers and forelimbs for their movement. They are warmblooded and have four-chambered heart. Examples are ducks, pigeons, and sparrows, etc
• Mammalia -The distinctive feature of this class is the presence of mammary glands and hairs on the body. They are warm-blooded and have four-chambered heart. They are milk-producing creatures: Humans, rats, monkeys, and lions belong to the Mammalia class

Some characteristic features of subphylum Vertebrata

• The animals belonging to the subphylum Vertebrata have vertebral columns
• The central nervous system of the animals under this subphylum has the spinal cord and brain. The brain is enclosed in the skull (brain box)
• The subphylum Vertebrata have 2 to 4 chambered heart. 2 chambered heart are found in fishes. Three chambered in amphibians and four chambered in human and birds
• Another distinctive characteristic of vertebrates is the presence of a hepatic portal system. The hepatic portal system is a system of veins that carry deoxygenated blood to the liver for detoxification. They are present in all vertebrates
• Haemoglobin is found in the red blood cells in the vertebrates
• A pair of kidneys are present in vertebrates to eliminate the waste for excretion
• Gills, skin and lungs are used for respiration. Fishes use Gills and frogs use skin in particular conditions. Lungs are used by amphibians, reptiles, birds and mammals
• The endoskeleton of animals in the subphylum Vertebrata is either made up of bones or cartilage or both in some animals
• The exoskeleton is made up of hairs, scales and feathers. Hair in the case of mammals. Scales in the case of  fishes and feathers in the case of birds
• Vertebrates are unisexual

Conclusion

In short, the subphylum Vertebrata is a subdivision of the phylum Chordata. The organisms grouped under Chordata have a notochord (a primitive backbone form). The distinctive features of the subphylum Vertebrata are the vertebral columns in place of the notochord. The central nervous system of vertebrates is properly distinguished into the brain and spinal cord. Other unique features include the hepatic portal system and chambered hearts. Subphylum Vertebrata is divided into Agnatha and Gnathostomata. Animals in Agnatha are jawless vertebrates and Gnathostomata have jaws in their mouths. Agnatha is further classified into Cyclostomata. Finally, Gnathostomata is divided into Pisces and Tetrapoda.