| A | B |
|---|
| Hemichordata | the "link" between vertebrates and invertebrates |
| Hemichordata | phylum to which the acorn worm belongs |
| birds and mammals | vertebrates with 4-chambered heart |
| amphibians and reptiles | vertebrates with 3-chambered hearts |
| fish, amphibians, reptiles | cold-blooded vertebrates |
| birds and mammals | warm-blooded vertebrates |
| notochord | rod-like supporting structure |
| nerve cord | conducting rod between the body and the brain |
| urochordata | phylum to which sea squirts belong |
| urochordata | phylum which loses its notochord in adult stage |
| amphioxus | another name for the lancelet |
| cephalochordata | subphylum to which the lancelet belongs |
| vertebrata | subphylum to which animals with backbones belong |
| agnatha | class to which hagfish and lamprey belong |
| agnatha | the jawless fishes |
| chondrichthyes | the cartilaginous fishes |
| chondrichthyes | sharks and rays |
| fish | vertebrates with two-chambered hearts |
| amphibians and reptiles | vertebartes with three-chambered hearts |
| birds and mammals | vertebrates with 4-chambered hearts |
| aves | another name for the class, "birds" |
| reptiles, birds, mammals | vertebrates with internal fertilization |
| mammals | the only class of vertebrates which gives live birth |
| amphibia | name meaning "two lives" |
| agnatha, chondricthyes | vertebrate classes with cartilaginous skeletons |
| osteichtyes | have an operculum and swim bladder |
| chondrichtyes | have placoid scales |
| amphibians | breathe using gills then with lungs |
| reptilia | first to lay eggs with amniotic sac |
| birds | toothless vertebrates |
