The Term Vertebrates and it’s Characteristics.


These are animals with backbone or vertebral column in their body. They are called Chordata. They are divided into five classes, these are:

  • 1. Pisces (Fishes).
  • 2. Amphibian (Amphibians).
  • 3. Reptilian (Reptiles).
  • 4. Aves (Birds).
  • 5. Mammalians (Mammals).


1. They possess an internal jointed skeleton made up of cartilage or bone.

2. They have bilaterally, symmetrical bodies.

3. They have two pair of limbs. The Pectoral limbs from the fore-limbs or wings while the pelvic limbs from hind limbs or legs.

4. They have well developed central nervous system with brain and spinal chord.

5. They have a closed blood vessels and the heart.

6. They have efficient excretory organs such as Kidneys.

7. They possess Skin, which may have a covering of Scales, Hairs or Feathers.


The term Pisces (Fishes) is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail.


  • 1. They are aquatic animals i.e. they can be found in marine or fresh water, ponds, lake and rivers e.t.c.
  • 2. The skin is covered by scale but few are without scales.
  • 3. They have fins which are used for movement in water.
  • 4. They are Pokilothemic or cold-blooded animals i.e. their body temperature varies with that of its environment.
  • 5. They have gills which are used for gaseous exchange.
  • 6. They have lateral line system, this is used for dictation of vibration and pressure in water.
  • 7. Reproduction is sexual and they have external fertilization.
  • 8. They are Oviparous animals i.e. they lay eggs which develop to adult stage outside the body of the adult female fish.


1. BONY FISH: These are fishes with bony skeleton e.g. Tilapia, Corp, Salmon, Mackerel and Unerring e.t.c.

2. CARTILAGINOUS: These are fishes whose bones are made of cartilages.


Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.


  • 1. They are poikilothermic or cold-blooded animals.
  • 2. They have two pair of limbs- forelimbs and hind-limbs.
  • 3. They carry out gaseous exchange (Respiration) by Gills, Lungs, Skin and Mouth.
  • 4. A Reproduction is sexual while fertilization is external.
  • 5. The young ones (Tadpoles) are herbivores while adult are carnivores.
  • 6. They have poisonous glands on their skin which are used for defense.
  • 7. They exhibit dual li fe, i.e. they can live in water and land.

Examples are: Toads, Frogs, Salamander and Newts.


Reptiles, as most commonly defined, are the animals in the class Reptilia, a paraphyletic grouping comprising all amniotes except synapsids and Aves.


  • 1. They are poikilothermic or cold-blooded animals.
  • 2. They have dry skin covered with scales.
  • 3. They have two pairs of limb except snakes.
  • 4. Some are aquatic animals e.g. Crocodile and Turtles while others are terrestrial animals e.g. Snakes and Lizard.
  • 5. They have lungs which are used for gaseous .
  • 6. Reproduction is sexual and fertilization is internal.
  • 7. They have oviparous mode of reproduction i.e. the female lay fertilized eggs.
  • 8. They have Homodont dentition.
  • 9. They do not show parental care to their offsprings (young ones).

Examples are: Lizard, Wall gecko, Tortoise, Snake and Crocodilians e.t.c.


Birds are a group of warm-blooded vertebrates constituting of the class Aves, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.


  • 1. They are homoeothermic or warm-blooded animals they have constant body temperature.
  • 2. Their entire bodies are covered with feathers except the hind legs which are covered with scales.
  • 3. They have wings which are used for flight.
  • 4. They have beak (without teeth) which is used for feeding.
  • 5. They have rigid and hallow with air sacs which make them light during flight.
  • 6. Reproduction is sexual and fertilization is internal.
  • 7. They exhibit oviparous mode of reproduction.
  • 8. They have lung which are used for gaseous exchange.
  • 9. They show parental care for young ones.

Examples are: Pigeons, Domestic fowl, Ducks, Ostrich, Weaver, Birds, Wood Peckers, Hawks, Sparrow e.t.c.


Mammals are a group of vertebrate animals constituting the class Mammalia, and characterized by the presence of mammary glands (Breast) which in females produce milk for feeding their young, a neocortex, fur or hair, and three middle ear bones.


  • 1. They are homoeothermic or warm-blooded animals.
  • 2. Their bodies are covered with hairs.
  • 3. They have heterodont dentition i.e. they have different sets of teeth.
  • 4. Their internal cavity is divided into chest and abdomen by muscular diaphragm.
  • 5. They have ling which are used for gaseous exchange.
  • 6. They have two pairs of limbs.
  • 7. The skin contains glands e.g. Sweat, Sebaceous and Mammary gland.
  • 8. Reproduction is sexual and fertilization is internal.

Examples are: Man, Rabbit, Rat, Whale, Bats, Monkey, Goat and Lion e.t.c.


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