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Classification of chordates:

They have 45,000 species

    Generally, classified into 3 Sub-Phylums.

(1)

Sub-Phylum Urochordates

(2)

Sub-Phylum Cephalochordates

(3)

Sub-Phylum Craniata

1. Sub-Phylum Urochordates:

  • Their notochord, nerve cord, and post-anal tail are present only in free-swimming larvae.

  • Adult are sessile, Plankton depender, and enclose in a tunic
  • They are marine

They have three classes

 (i)

Class-Ascidiacea

(ii)

Class-Appendicularia

(iii)

Class-Thaliacea

i.    Class-Ascidiacea:

These all are sessile, solitary, or colonial

Example:

Sea squirts, ascidians, ciona.

ii.    Class Appendicularia:

  • They are Planktonic.
  • Their adults retained the tail and notochord
  • Barrel-shaped
  • They are lacking cellulose-containing tunic

Example:

Fritillaria

iii.    Class-Thaliacea:

  • They are also Planktonic or filter feeders
  • Their adults are tailless
  • They are also barrel-shaped
  • They have a tunicates

Example:

Salpa

2. Subphylum Cephalochordates:

  • Their body lateral compressed and transparent
  • They have 5 distinguish characters throughout the life

Example: Amphioxus or Branchio-Stomata

3.    Sub-Phylum Craniata:

  • Skull surrounds the brain's olfactory organs, eyes, and inner ears.

Craniata divided into 2-infra-Phylum

(i)    Sub-Phylum Craniata:

Sub-Phylum Craniata has two infra-Phylum:

(a)

Infra-Phylum Hyperotreti

(b)

Infra-Phylum Vertebrata

(a)    Infra-Phylum Hypertreti:

  • Fish-like, skull consisting of cartilaginous bars, jawless, 4-pairs of Tentacles.
  • 5-15 pairs of pharyngeal slits.
  • Ventrolateral slime glands.

Example: Hag-Fishes

(b)    Infra-Phylum Vertebrata:

  • Notochord, nerve chord, Post anal tail, and pharyngeal slits are present at least in embryonic stages.
  • Vertebrae surround nerve chords and serve as primary axial support.

Vertebrata have 8-classes

(i)

Class Pteromyzontida

(ii)

Class Chondrichthyes

(iii)

Class Actinopterygii

(iv)

Class Sarcopterygii

(v)

Class Amphibia

(vi)

Class Reptilia

(vii)

Class Aves

(viii)

Class Mammalia

i.    Class Pteromyzontida:

  • They are fish-like
  • Jawless
  • No pair appendages
  • Cartilligenous skeleton
  • Sucking mouth with teeth and rasping tongue.

Example: Lamprey

ii.    Class Chondrichthyes:

  • Fish like or cartilaginous fishes.
  • Jaws pair appendages and cartilaginous skeleton is present
  • No swim bladders

Examples:    Skates, rays, sharks

iii.    Class Actinoptyrygii:

  • Bony fishes have paired fins supported by dermal rays.
  • The basal portion of paired fins is not especially muscular.
  • Pneumatic sacs functions as a swim bladder

Examples: Ray-finned fishes

iv.    Class Sarcopterygii:

  • Bony fishes have paired fins with muscular lobs.
  • Pneumatic sacs functions as lungs
  • Atria and ventricles are at least partially divided.

Examples: lungs fishes and tetrapods

v.    Class Amphibia:

  • Skin with mucoid secretion
  • Possessing lungs and gills
  • Moist skin serves as a respiratory organ

Examples: frogs, toads, and salamanders

vi.    Class Reptilia:

  • Dry skin with epidermal scales.
  • Amniotic eggs
  • Terrestrial embryonic development

Examples: snakes, lizards, alligators.

vii.    Class Aves:

  • They have feathers used for flight
  • Pneumatic bones
  • They are endothermic (warm-blooded)
  • Having amniotic eggs

Examples: birds, such as crow

viii.    Class Mammalia:

  • Body at least partially covered by hairs.
  • Endothermic
  • Young nourishes from mammary glands.

Examples: mammals such as humans, cats, dogs.


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