CHORDATE ANATOMY 



rentury, and called the Linnaean, or binomial, system. Thus all birches 

 are called by their Latin name Betula, and that is their genus. White, 



4AMMALS^ 

 17000 SPJ 



BIRDS 

 20.000 SP. 



INSECTS 

 500. 000 SP. 



AMPHIBIANS^ 

 180*0 SR 



:ptii 

 iooosp; 



IRUSTACEAl 

 8000 SR 



Varachnidsi 

 »,5ooosp; 



annelids 

 4boosf 



R0TIFERS1 

 850^ 



THREADWORMS, 

 1600 SR 



MOLLUSCS. 

 61.000 SR 



uroch6rds 



I40p SB 

 |MOL^~^ 

 LUSCOIDS 

 l>00S 



/HE Ml 

 /CHORDS 



FISHES. 

 J2.000SR 



CYCLOSTOMES 



CEPHALOCHORDS 

 22 SR 



J. 



-SP^ECHINODERMS. 

 10,000 SR, 



FLAi;WORMS^ 

 4500 SR 



SPONGE 

 250 OSE 



(COELENTERATES 

 V7000 SP.y 



>ROTOZOA] 

 10,000 SP.. 



A PHYLOGENETIC TREE OF THE ANIMAL KINGDOM. 



Fig. 



-A phylogenetic tree of the animal kingdom, showing the dichotomy 

 animals into Prnterostomians and Deuterostomians. 



yellow, and black birches are therefore respectively, as species, Betula 

 alba, Betula lutea, and Betula nigra; but the American white birch is 

 Betula papjrrifera, that is, the paper birch; and the common gray birch 



