- spiral embryonic cleavage
- mesoderm splits=coelom formation
- blastopore becomes the mouth
- radial embryonic cleavage
- gut outpocket=coelom formation
- blastopore becomes the anus
features of chordates
(Anthro.Palomar.Edu, and Vertebrates, p.82):
1 - a dorsal, nerve tube;
2 - lateral, pharyngeal gill slits or pouches, to extract O2 from water in embryonic stage;
3 - notochord - a rudimentary, dorsal (along back), internal skeleton of stiff cartilage, above which runs a hollow nerve cord;
4 - a post-anal tail; and
5 - an endostyle.
(3 SUB-PHYLA OF CHORDATES)
Emergent Vertebrates II
vertebrate: also called craniata, an animal derived from the phylum: chordates, sub-phylum vertebrata, having a backbone and bony skull that partly encloses a central nervous system. The hollow, dorsal nerve tube is now replaced by the spinal cord, which is now protected by a segmented vertebral, or spinal, column, composed of cartilage and/or bone. The head and brain house paired sense organs, that coordinate movement and sensation. Fish were the first vertebrates. Sub-phylum vertebrata includes 8 classes, including 4 classes of fish (including agnatha, chondrichthyes, and osteichthyes), and the additional classes: amphibia, reptilia, aves (birds), and mammalia (Anthro.Palomar.edu).