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Vertebrates are the most organized organisms on Earth. They belong to the sub-phylum Vertebrata. They are not the most numerous group of animals, they are the most advanced group of animals.The characteristics that makes vertebrates special are the presence of the spinal cords, vertebrae and notochords.


Most vertebrates have a very well developed nervous system. The vertebrates also have muscles and skeletons which help them move around efficiently and perform complex moves.

 Vertebrates include the majority of the Phylum Chordata, having about 64,000 species described. Vertebrates make about 4% of all described species. 

Vertebrates have a long history on earth - more than 500 million years, from the Cambrian era until date. First Vertebrates have said to be appeared around the Cambrian period of the Paleozoic era about 525 million years ago, they are said to be adapted to feeding algae in shallow waters and moving around from place to place. 


Vertebrates Defintion

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Vertebrate are the animals belonging to the sub-phylum Vertebrata. They belong to the Phylum Chordata. The characteristics of phylum chordata is the presence of notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. The members of subphylum Vertebrata possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult. All vertebrate are chordates but all chordates are not vertebrates. Special characteristics of vertebrates other than the vertebral column are, they have a muscular heart which is two, three or four chambered. For excretion they have kidneys and appendages that are paired which may be fins or limbs.

Vertebrate Characteristics

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General characteristics of the sub-phylum Vertebrata are as follows: 
  • Vertebrates have a well developed brain.
  • Brain is set inside a bony box, known as cranium.
  • Notochord is present in all chordates during sometime of development, it is formed on the dorsal side of the primitive gut in the early embryo stage.
  • Most vertebrates possess guts with a non-terminal anus. 
  • The mouth cavity and the oesophagus is connected by the pharyngeal gill slits to a muscular tube pharynx, which opens to the exterior.
  • They possess a dorsal hollow nerve tube at some stage of their life. 
  • Possess a dorsal cartilaginous nerve rod known as the notochord. 
  • At some stage of their life possess gill slits in the pharyngeal region.
  • Have partially open circulatory system.
  • Possess two pairs of appendages.
  • The endoskeleton is made of cartilage or bone.
  • The first vertebrates were jawless fishes with single caudal fin.
  • The advancement of vertebrates with a hinged jaw which opened new food options and jawed fishes became the dominant creatures in the sea.
  • All vertebrates have a heart and closed circulatory system.
  • Reproduction is normally sexual.
  • Feed on variety of organic materials.
  • Unisexual animals, have one pair of gonads.

Vertebrate Classification

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Vertebrata Classification
                                                              Classes of Vertebrates

Class - Cyclostomata

The living members of this class are all ectoparasites on some fishes. They have a elongated body. They bear 6-15 pairs of gills through which they respire. The mouth of the cyclostomes is sucking circular mouth without jaws. They do not have body scales and paired fins. The vertebral column and the cranium is cartilaginous. Circulation is closed type. These are marines organisms but  they migrate to fresh water for spawning. After metamorphosis their larvae returns to the ocean.

Example: Petromyzon (Lamprey), and Myxine (Hagfish).

Class - Chondrichthyes

These organisms are marine and have streamlined body. The endoskeleton is cartilaginous. Mouth is located ventrally and the notochord is present throughout life. The gills are separate and are not covered by the operculum. The skin contains minute placoid scales. The placoid scales are modified as teeth and the jaws are powerful. They are predaceous animals. Air bladder is absent in these animals, hence, they have to swim constantly to avoid shrinking.

Example: Scolidon, Pristis, Trygon.


Class - Osteichthyes

This class includes animals that are both marine and fresh water fishes with bony endoskeleton. Their body is streamlined. Mouth is terminal in position. The gills are covered with operculum on each side and are in four pairs.The skin is covered by ctenoid/cycloid scales. Air bladder is present, it regulates buoyancy. Two-chambered heart is present, with one auricle and one ventricle. They are poikilothermic animals. The sexes are separate, fertilization takes place externally. Most of them are oviparous animals and development is direct, with no larval stages.

Example: Hippocampus, Clarias.

Sea Horse

Class - Amphibia

The name Amphibia indicates - from Greek, Amphi meaning dual and bios meaning life. 

Ampibians can live both in aquatic and terrestrial habitats. These animals have two pairs of limbs. Body is divisible into head and trunk and tail is present in some animals. The skin of these animals are scaleless and moist. The eyes have eyelids, and the ears are represented by a tympanum. Cloaca is a opening to the exterior, it is a common chamber for the alimentary canal, urinary and reproductive tracts.Gills, lungs and skin aids in respiration. Heart is three-chambered. They are cold-blooded animals. Sexes are separate, fertilization is external. They are oviparous animals and development is indirect. 

Example: Toad, frog, salamander.


Class - Reptilia

In Latin repere or reptum means to creep or crawl, hence, the class name refers to locomotion that is of creeping or crawling mode. 

These animals are mostly terrestrial and their body is covered dry and cornified skin, epidermal scales or scutes. External ear opening is absent, tympanum represents the ear. Limbs, if present are of two pairs. Usually heart is three-chambered, but is four chambered in crocodiles. They are poilkilothermic animals. Some animals like the snake and the lizards shed their skin. Sexes are separate, internal fertilization takes place. They are oviparous and development is direct. 

Example: Turtle, Chameleon, crocodile.


Class - Aves

Most of the members can fly, except the flightless birds. The characteristic feature of birds is the presence of feathers. The forelimbs are modified as wings. The hind limbs are modified for walking, swimming or clasping and generally have scales. The skin is dry and does not have glands, except a oil gland at the base of the tail. Endoskeleton is bony, and the bones are hollow with air cavities known as pneumatic bones. Heart is four-chambered completely. They are warm-blooded animals. Lungs are the organs of respiration. Sexes are separate, fertilization is internal. They are oviparous animals and development is direct. 

Example: Crow, Pigeon, Parrot etc.


Class - Mammalia

Mammals are present in almost all habitats - polar ice caps, deserts, mountains, forests, and grasslands.The unique characteristic of the class mammalia is the presence of milk producing glands (mammary glands), by which the young ones are nourished. The limbs are of two pairs. The skin is covered with hairs. External ear 'pinna' is present. Heart is four-chambered and they are homeothermic animals. Respiration is through lungs. Sexes are separate and fertilization is internal. They viviparous animals, with direct development. 

Example: Kangaroo, Tiger, Lion, Platypus etc. 

List of Vertebrates

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The vertebrates are a very diverse group of animals ranging from Hag-fish to Man. There are not the most numerous group of animals. Vertebrates are interesting because we are intimately familiar with them, or species Homo sapiens is included within the sub-phylum vertebrata. Vertebrates are easy to find as we co-exist with them and often aware of their presence in our environment. 

Below are the list of few very familiar vertebrates: deer, fish, dogs, cats, birds, snakes, lizards, kangaroo, bears, foxes, wolves, bat, monkeys, eagles, penguins etc.

Examples of Vertebrates

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Below are the examples of vertebrates:

Pisces: Sharks, trouts, eels, tunas, seahorse, pirahnas, salmons, etc.

Amphibians: Salamanders, frogs, toad, newts, caecilians, etc.

Reptiles: Snakes, lizards, tortoise, turtles, crocodiles, gharials, alligators, etc.

Birds: Penguins, emu, eagles, ostrich, parrot, crow, pigeon, ducks, owls, kites, robins, woodpeckers, albatross etc.

Mammals: Kangaroo, echidna, platypus, bats, mice, tigers, moles, dolphins, whales, deer, gorrilas, lemurs, rabbits, wolves, lions, leopards, jackals, etc.

More topics in Vertebrates
Animal Tissue
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