Phylum Chordata
Phylum Chordata
• The chordates occupy the highest position in the food chain.
• The name phylum was derived from the characteristic which all chordates share, the notochord – a long, elongated, and flexible cartilaginous structure that runs the entire length of the body. (Gr. noto = the back; chorde = string)
Characteristics:
• A dorsal nerve cord located above the notochord, it runs the entire length of the body. The nerve cord is a bundle of nerve fibers that connects the brain to the different parts of the body.
• Presence of pharyngeal slits which are openings between the throat and the outside it’s also modified to filter food and gaseous exchange. The pharyngeal slits are supported by gill arches which also had been greatly modified.
• Presence of post-anal tail, an extension of notochord that extends beyond the anus.
• They are bilaterally symmetrical body plan.
• Important: It differentiates them from other animals is the presence of two appendages. These appendages are highly modified for locomotion.
Different Groups of Chordates:
• Invertebrate chordates
-are the chordates whose notochords remain during the entire life of the organisms.
• Vertebrate chordates
-are the chordates that have notochord and pharyngeal slits during early stages of development.
Invertebrate chordates
• Cephalochordota(cephalo = head)
- Is represented by the lancelet or amphioxus, a chordate with a fishlike appearance.
• Tunicata
-Is an unusual chordate that lives attached to the seabed. The swimming larva of the organism contains the notochord, and all the rest of the distinguishing features of the chordates.
Vertebrate chordates(7 classes)
Three Classes of Fish:
• Class Agnatha(a = not, without; gnathos = jaw).
-This is represented by the lamprey, an eel shaped jawless fish that is considered as
• The chordates occupy the highest position in the food chain.
• The name phylum was derived from the characteristic which all chordates share, the notochord – a long, elongated, and flexible cartilaginous structure that runs the entire length of the body. (Gr. noto = the back; chorde = string)
Characteristics:
• A dorsal nerve cord located above the notochord, it runs the entire length of the body. The nerve cord is a bundle of nerve fibers that connects the brain to the different parts of the body.
• Presence of pharyngeal slits which are openings between the throat and the outside it’s also modified to filter food and gaseous exchange. The pharyngeal slits are supported by gill arches which also had been greatly modified.
• Presence of post-anal tail, an extension of notochord that extends beyond the anus.
• They are bilaterally symmetrical body plan.
• Important: It differentiates them from other animals is the presence of two appendages. These appendages are highly modified for locomotion.
Different Groups of Chordates:
• Invertebrate chordates
-are the chordates whose notochords remain during the entire life of the organisms.
• Vertebrate chordates
-are the chordates that have notochord and pharyngeal slits during early stages of development.
Invertebrate chordates
• Cephalochordota(cephalo = head)
- Is represented by the lancelet or amphioxus, a chordate with a fishlike appearance.
• Tunicata
-Is an unusual chordate that lives attached to the seabed. The swimming larva of the organism contains the notochord, and all the rest of the distinguishing features of the chordates.
Vertebrate chordates(7 classes)
Three Classes of Fish:
• Class Agnatha(a = not, without; gnathos = jaw).
-This is represented by the lamprey, an eel shaped jawless fish that is considered as