Phylum: Chordata, its classification and characteristics

The characteristics of this phylum are as follows:

  1. Presence of notochord
  2. Presence of dorsal hollow (tubular) nerve cord.
  3. Presence of pharyngeal gill slits.
  4. Post anal tail is present.

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This phylum is classified into four sub-phylum. They are as follows:

Sub- phylum 1: Hemichordata

  • Marine animals.
  • Simple worm-like soft bodied animal.
  • Remain buried under mud or sand along the sea shore.
  • Body is divisible into three regions. They are proboscis, collar and trunk.
  • Notochord is restricted in the anterior region. Also called buccal diverticulum due to its doubtful nature.
  • Many pairs of gill slits are present.
  • Nervous system is simple consisting of subepideural nerve plexus.
  • Blood vascular system is simple.
  • Sexes are separate. Fertilization external in sea water.
  • Free swimming tornaria larvae present which resembles to echinoderm larva.
  • Includes about 80 species.
  • Examples: Balanoglossus, Cephalodiscus, Atubaria, etc.

Phylum Chordata: An Overview, Classes, Characteristics, Examples

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Sub-phylum 2: Urochordata (Tunicata)

  • Gr. Uros- tail +chordate– notochord.
  • Marine animals found in all parts of the sea and at all depths.
  • Commonly called “ascidians” because of general appearance to askidian.
  • Usually sedentary or some are free living.
  • Called tunicate as the entire body is covered by tunic or test made of tunicine.
  • Distal end with two openings called bronchial or oral pore and the atrial siphons.
  • Notochord and nerve cord are found in tail region of tadpole larvae.
  • Adult animals show perforated pharynx.
  • Adult body degenerate, sac-like, unsegmented usually without tail.
  • Heart is ventral, tubular and enclosed in pericardium.
  • No locomotory organ.
  • Hermaphrodite in nature.
  • Fertilization cross and external.
  • Development indirect.
  • Asexual reproduction by budding.
  • Includes about 2100 species.
  • Examples: Herdmania, Salpa, Doliolum, etc.

Chordates An Introduction. Kingdom Animalia- All inverts & verts 1.Phylum  Chordata: All have nerve cords. 3 subphyla : A- Urochordata (tunicates aka  sea. - ppt download

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Sub-phylum 3: Cephalochordata

  • Gr. Kephalo- head + Chorde– cord.
  • Small fish like animals, live in the sand of sea shore.
  • Notochord and nerve cord are persistent and extend along the body.
  • Mostly sedentary.
  • Nerve cord is tubular and dorsal.
  • Pharynx is large and sac like perforated by numerous gill slits.
  • Ciliary feeding animals.
  • Definite coelom is present.
  • Excretion through definite nephridia.
  • Lacks distinct head and paired appendages.
  • Body has trunk and tail.
  • Circulatory system well developed, closed and without heart.
  • Respiratory pigment is absent.
  • Sexes are separate.
  • Fertilization external in sea water.
  • Development is indirect including a free swimming larva.
  • No asexual reproduction.
  • Includes only 15 species.
  • Examples: Amphioxus (Branchiostoma),  Asynnetron, etc.

Sub-phylum 4: Vertebrata (Craniata)

  • Notochord replaced by vertebrae and called vertebral column or back bone.
  • Brain inside cranium so called craniata as well.
  • Body triploblastic and bilaterally symmetrical.
  • Lower vertebrates aquatic, higher terrestrial.
  • Body consists of head, trunk and post-anal tail.
  • Two pairs of lateral appendages in trunk region.
  • In some cases appendages are reduced or absent.
  • Skin consists of two layers outer epidermis and inner dermis.
  • One pair of kidneys as excretory organ.
  • Circulatory system is closed type.
  • Blood is red and hemoglobin is present in RBCs.
  • Organ-system grade of body organization.
  • Endoskeleton of cartilages or bones or both.
  • Endocrine glands secreting hormone to regulate body function.
  • Sexes are separate.
  • Examples: Labeo, Scoliodon, Homo sapiens, etc.




Phylum: Chordata, its classification and characteristics