write the main characteristics of chordates
Answers
They are bilaterally symmetrical and triploblastic.
Chordates are coelomate and show an organ system level of organisation.
They have the characteristic notochord, dorsal nerve cord, pharyngeal slits.
Also, they have a post-anal
In this phylum, the nervous system is dorsal, hollow and single.
The heart is ventral, with a closed circulatory system.
The habitat of these animals is widespread. So we can find them in the marine environment, fresh waters as well as terrestrial environments.
Four distinctive derived characteristics of chordates distinguish them from their ancestors:
A. Notochord, or a rod of vacuolated cells, encased by a firm sheath that lies ventral to the neural tube in vertebrate embryos and some adults.
B. Hollow nerve cord that lies dorsal to the notochord
C. Pharyngeal pouches
D. Endostyle - elongated groove in the pharynx floor of protochordates that may develop as the thyroid gland in chordates
In the subphylum Vertebrata, all members possess the four chordate characteristics at some time in development, but often these structures are altered significantly in adult animals.
These four characteristics may be found in some of the ancestors of chordates and are commonly placed in an informal grouping called Protochordates. These serve as living representations of the missing fossils in vertebrate evolution.