Phylum Chordata: Introduction to Phylum Chordata, Features of Chordates (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction to Phylum Chordata

• Phylum Chordata possess a bilaterally symmetrical body and presence of notochord is most distinguishing character that all animals belonging to this phylum.
• It belongs to the Kingdom Animalia and includes all the vertebrates, i.e.. , animals with a backbone along with several invertebrates, i.e.. , organisms without a backbone.

Features of Chordates

Notochord

• Its main function is to support the nerve cord.
• The vertebral column replaces the notochord in vertebrate animals.
• Notochord further consists of a longitudinal rod that is made of cartilage and runs between the nerve cord and the digestive tract.

Dorsal Nerve Cord

A bundle of nerve fiber which connects the brain to the muscles and other organs.

Post-Anal Tail

The tail has skeletal muscles in some chordates which help in locomotion.

Pharyngeal Slits

• These are the openings connecting the mouth and the throat.
• The entry of water through the mouth is allowed without entering the digestive system.
• This is the third largest phylum in the subphylum Vertebrata.

Division of Phylum Chordata

Urochordata

• It is also known as Tunicata because the body of an adult is enclosed within a tunic made up of cellulose like substance known as tunicin.
• A dorsal ganglion in adults replaces the nerve cord present in larva.
• The larva can move and undergoes metamorphosis.
• For e. g. Ascidia, Salpa, Doliolum.

Cephalochordata

• The tail is present throughout the life.
• Progressive metamorphosis is shown.
• The notochord is found throughout life.
• For e. g. Lancelets possess the notochord and nerve cord throughout their life.

Vertebrata

• These contain advanced chordates and have cranium around the brain.
• A high degree of cephalization is observed.
• They have a well-developed coelom (the principal body cavity in most animals) .
• The alimentary canal is complete.
• For e. g. in Humans.