Question

1: disscus the phylum chordata.

2: Is chordata a monophyletic group? how?

3? when does this group first appear in the fossil record?

4? list and explain the four synapomorphies of the phylum overall.

5? briefly describe the three subphla within chordata and also describe the evolutionary inovations unique to the groups vertebrata and Gnathostomata.

thank you.

Answer 1

Answer 1 phylum chordata. The main characteristics are.

Presence of notochord, dorsal hollow nerve cord, pharyngal slits, post anal tail.

Answer 2. Yes chordata is monophyletic group because it consist of all the chordates which are descendants of common ancestor which was also a chordate.

Answer 3. The synapomorphies of chordates are Notochord, single dorsal hollow nerve cord, pharyngeal pouches/slits, endostyle, and postanal tail.

Answer 5 there are three subphyla of chordata.

Urochordata : they have common characteristics such as gill pouches (slits), notochord, dorsal nerve cord. These are commonly small, sessile marine organisms. They do not have notochord, they just have ganglion. Notochord appear in only larval stage .

Cephalochordata: it has Amphioxus, which is a marine small and found in shallow region. It have true notochord, also there is a dorsal hollow nerve cord but brain is not true.

Vertebrate : they posses the vertebratal column. Includes all chordata characters.

Vertebrate unique character are they have vertebral column, they are craniata means have brain. They have skeleton made up on bones.

Gnathastomata : they have mouth which jaws structure, they include amphibians, mammals, aves and fishes.