Vertebrata General Characteristics, Classification and Examples | Free Biology Notes

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Vertebrata General Characteristics

• Presence of brain box and vertebral column
• Notochord initially is embryonic, replaced by vertebral column in adult
• The circulatory system is closed with ventral chambered heart
• The blood plasma contains RBC and WBC
• Gill slits are limited in number (usually 5 pairs)
• Two pairs of appendages present
• Nerve cord is differentiates into brain and spinal cord

Classification of Vertebrata

Subphylum vertebrata is divided into 2 divisions such as, Agnatha, the division which lacks jaw and Gnathostomata, the division which bears jaw.

Division 1. Agnatha

• Most of the members of this class are marine
• These fishes are ectoparasite as well as scavenger
• They have elongated body with 6-15 pairs of gills slits for respiration
• They have a sucking and circular mouth without jaws
• Scales and paired fins absent
• Notochord and vertebral column both are present. bones are absent
• Circulation is closed type, 2 chambered heart.
• Animals unisexual, fertilization external and larval stage is absent
• E.g. Petromyzon, Myxine etc.

Division 2. Gnathostomata

• Two well formed jaws encircle the mouth aperture in all members of this group.
• Paired and in some cases jointed appendages are present in Gnathostomata.
• Calcified, bony skull and vertebra are characteristic features of Gnathostomata.
• Divided into 2 super classes:- Pisces and Tetrapoda

Superclass 1. Pisces

• All aquatic and cold blooded fishes
• Body is long, spindle shaped and streamlined, which is divided into head, trunk and tail
• Body is covered by dermal scales, denticles or bony plates
• Locomotion with the help of various fins
• Respiration by gills
• Heart is two chambered, having one auricle and one ventricle
• External and middle ears are absent
• Lateral line system is well developed. help to sense water current vibrations
• Fishes are unisexual. Fertilization is internal or external and Development is direct
• Oviparous, viviparous or ovoviviparous
• Super class Pisces classified into two classes:- Chondrichthyes and Osteichthyes

Superclass 2. Tetrapoda

• Tetra-four, podos-feet
• Primarily terrestrial, some are secondarily aquatic in.
• Two pairs of pentadactyl limbs.
• Body covered by an exoskeleton of epidermal hair, feathers or scales.
• Lungs are main respiratory organs. Amphibian may respire by gills, skin or lungs.
• 3 or 4 chambered heart present.
• They are divided into 4 classes: Amphibia, Reptilia, Aves and Mammalia