Question

Which of the following is not a characteristic feature of all the chordates ?

• A. Presence of coelom
• B. Pharyngeal gill clefts in the early embryonic stages
• C. A diaphragm that separates thorax from abdomen
• D. Dorsal nerve cord

Answer 1

The Correct Option is C

Main characteristics of phylum Chordata are as follows :
1. Bilateral symmetry; segmented body; three germ layers; well developed coelom.
2. Notochord (a skeletal rod) present at some stage in the life cycle.
3. Single, dorsal, tubular nerve cord; anterior end of cord usually enlarged to form brain.
4. Pharyngeal pouches present at some stage in the life cycle; in aquatic chordates these develop into gill slits.
5. Postanal tail, usually projecting beyond the anus at some stage but may or may not persist.
6. Segmented muscles in an unsegmented trunk.
7. Ventral heart, with dorsal and ventral blood vessel; closed blood system.
8. Complete digestive system.
9. A cartilaginous or bony endoskeleton present in the majority of members (vertebrates).
10. Presence of diaphragm is the characteristic feature of vertebrates $eg$, Mammals.