It belongs to the subphylum Vertebrata of phylum Chordata. The name Vertebrata is derived from the presence of serially arranges “vertebrae” or vertebral column or the BACKBONE which comprise a major part of their axial exoskeleton. Another diagnostic character is the elaboration of the anterior skeletal elements into the “cranium” or skull which houses various sensory organs and the brain. Therefore also called CRANIATA.
Vertebrae may be defined as a special kind of chordate animal that has a cartilaginous or bony endoskeleton consisting of a cranium, housing a brain vertebral column through which the nerve cord passes. No other group of animals possess these two fundamental and related characteristics which have existed since the late Cambrian and Ordovician.
GENERAL CHARACTERISTICS:
- +nce of the vertebral column.
- +nce of skull or cranium hence the name Craniata.
- +nce of the notochord, pharyngeal gill slits and dorsal hollow nerve cord.
- Lower vertebrates are aquatic, and higher vertebrates are predominantly terrestrial.
- Body medium to large
- Bilaterally symmetrical
- Metamerically segmented
- Body made of —–head
——trunk
——postanal tail
the neck might be present, especially in the terrestrial form
- The trunk bears 2 pairs of jointed appendages, reduced or absent in some, but if present serves as support and locomotion primarily
- INTEGUMENTS is stratified epithelium made of an outer epidermis made of the outer—–epidermis
inner—–dermis
- presence of mucosal glands in aquatic species
- Skin is covered by a protective exoskeleton comprising scales, feathers, hairs, claws, nails, horns, etc.
- Colome—–large
—–develops as schizocoel
—–largely filled with the visceral systems
- notochord stops short beneath the forebrain, invested by cartilage or bone, or replaced by a vertebral column
- a living jointed endoskeleton of bone or cartilage or both including the skull, vertebral column, girdles and limb bones.
- A living jointed endoskeleton of bone or cartilage or both, including the skull, vertebral column, girdles and limb bones.
- Many muscles are attached to the endoskeleton for motion and locomotion
- DIGESTIVE CANAL —-convoluted
- LIVER—–massive, not tubular
- PHARYNGEAL GILL SLITS—-not more than 7 except for some cyclostomes
- RESPIRATION—-lower aquatic and aquatic forms
by gills
—–in terrestrial form by lungs
- BLOOD VASCULAR SYSTEM—closed
- HEART—-ventral
—-muscular
—-contractile
—-2/3/4 chambers
- EXCREATION—-paired by kidneys
—–mesonephric(the embryonic organ which is the second of the three excretory organs, permanent kidneys in amphibians and fishes replacing protonephrons during developmental and larval stages)
—–metanephric(permanent fully functional and highly complex kidney present in mammals)
segmental/non-segmental discharging through ducts into the cloacal or anal region.
- ANTERIOR END OF DORSAL NERVE CORD
- enlarges into a complex brain, protected by the skull.
- remaining nerve cord forming the spinal nerve cord surrounded and protected by vertebrae.
- 10 to 12 pairs of cranial nerves in the head, except in cyclostomes, the spinal nerves formed by the union of the dorsal and ventral roots which are given out in each segment.
- The dorsal and ventral nerve roots are separate in lower vertebrates like cyclostomes.
- In higher vertebrates, the two nerve roots are united and form a common spinal nerve.
- The ventral nerve in efferent or motor in nature carries impulses from the central nervous system to the effector organ
- while the dorsal nerve is mixed, it bears a swelling called SPINAL GANGLION.
- SPECIAL SENSORY ORGANS include pair of eyes and a pair of auditory organs, derived from part of the brain.
- ENDOCRINE SYSTEM of ductless glands scattered through the body regulating, body processes, growth and reproduction.
- SEXES separate
- gonad paired, Discharging sex cells through duct opening into the anus(cloaca), or near the anus(separate sex organs)
- DEVELOPMENT —-Direct/indirect
They are highly diverse groups of 49,000 species that exhibit Vertebrata and count in the Chordata group
40,000— extinct.
Kinds of vertebrates —–fishes
——–birds
——–amphibians
——–mammals
