Simulation · Biology · Class 11
Chordate or not, and where the notochord goes
From the lesson Chordates and non-chordates in Animal Kingdom. Change the values and watch what happens.
Chordate or not, and where the notochord goesBiology · Class 11
The idea behind it
NCERT §4.2.11, Table 4.1
- Chordates are defined by three features: a notochord, a dorsal hollow nerve cord and paired pharyngeal gill slits. They are also bilateral, triploblastic, coelomate, organ-system level, with a post-anal tail and closed circulation.
- Table 4.1 in brief. Chordates: notochord present; central nervous system dorsal, hollow and single; pharynx pierced by gill slits; heart ventral; post-anal tail present. Non-chordates: no notochord; nerve cord ventral, solid and double; no gill slits; heart dorsal where there is one; no post-anal tail.
- Chordata has three subphyla: Urochordata (Tunicata), Cephalochordata and Vertebrata. The first two are called protochordates and are all marine.
- In Urochordata the notochord is found only in the larval tail. In Cephalochordata it runs from head to tail and lasts through life. Examples: Ascidia, Salpa, Doliolum (urochordates); Branchiostoma, also called Amphioxus or lancelet (cephalochordate).
- Vertebrates have a notochord only in the embryo; in the adult it is replaced by a vertebral column of cartilage or bone. So every vertebrate is a chordate, but not every chordate is a vertebrate.
- On top of the chordate features, vertebrates have a muscular ventral heart with two, three or four chambers, kidneys that excrete and osmoregulate, and paired appendages in the form of fins or limbs.
- Vertebrata splits into Agnatha (no jaws: class Cyclostomata) and Gnathostomata (jaws). Gnathostomata has two super classes: Pisces with fins (Chondrichthyes, Osteichthyes) and Tetrapoda with limbs (Amphibia, Reptilia, Aves, Mammalia).