Exercises XII and XIII 



PLANT AND ANIMAL CLASSIFICATION 67 



(7) Appendages present or absent? If pres- 

 ent, jointed or not? 



(8) What is the nature and position of the 

 skeleton (exoskeleton or endoskeleton)? 



(9) Notochord or vertebral chord present or 

 absent? 



(10) What is the structure and position of vari- 

 ous organ systems? 



I. Protozoa (unicellular animals) 



1. PHYLUM PROTOZOA (Gr. protos, first; 

 zoon, animal). Single cells or loosely ag- 

 gregated colonies of single cells. Amoeba, 

 Euglena, Paramecium, Stentor, Volvox, etc. 



II. Metazoa (multicellular animals containing 

 specialized tissues) 



A. Parazoa (no true digestive cavity) 



2. PHYLUM PORIFERA (L. pours, porc ; ferre, 

 to bear). Sponges. Sessile; aquatic; diplo- 

 blastic; radially symmetrical body consist- 

 ing of cylinder closed at one end: budding 

 and folding of body often present; digestion 

 does not occur in central cavity but rather 

 in individual cells; generally a skeleton 

 present. 



B. Enterozoa (true digestive cavity present) 

 (a) Enterocoela (only cavity in the body is 

 the digestive cavity) 



3. PHYLUM COELENTERATA (Gr. koUoS, hol- 



low; enteron, intestine). Hydroids, jelly- 

 fishes, sea anemones, and corals. Diplo- 

 blastic; body may be tubular (polyp) or 

 bell- or umbrella-shaped (medusa); in some 

 organisms these forms alternate during life 

 cycle; budding to form colonies is common; 

 body is a double- walled sac; body cavity 

 is not separate from digestive tract; radiate 

 symmetry. 



4. PHYLUM CTENOPHORA (Gr. kterjos, comb; 

 p/wros, bearing). Sea walnuts, comb jellies. 

 Triploblastic (ectoderm, endoderm, and 

 mesoderm); radial combined with bilateral 

 symmetry; body with eight meridionally 

 arranged rows of swimming plates; a few 

 species are ribbon-shaped. 



(b) Coelomocoela (coelom present, tube- 

 within-tube structure) 

 (i) Nonsegmented 



5. PHYLUM PLATYHELMINTHES (Gr. platys, 



broad; helmintlws, worm). Flatworms. 

 Bilaterally symmetrical; no true segmenta- 

 tion, flattened dorsoventrally, no blood 

 vascular system; no anus; mostly parasitic. 

 The flatworms are triploblastic but don't 

 have a definite coelom. They do, however, 

 have gonocoels which represent a primitive 

 form of coelom. 



6. PHYLUM NEMATHELMINTHES (Gr. nematos, 

 thread; hehninthos, worm). Roundworms. 

 Bilaterally symmetrical; unsegmented; usu- 

 ally long and thin; most often contain an 

 alimentary tract with mouth and anus; 

 body cavity present; papillae or spines at 

 anterior extremity of body; both parasitic 

 and free-living forms. 



7. PHYLUM ROTIFERA (L. rota, v^\itt\; ferre, 

 to bear). Common small aquatic forms; 

 usually found in fresh water but also may be 

 marine and parasitic; ciliary movements on 

 anterior end suggest a rotating wheel; ner- 

 vous system present; body enclosed in flexi- 

 ble cuticle; body usually roughly cylindrical 

 tapering at posterior end to form a foot; 

 well-developed digestive system with mouth, 

 pharynx, glandular stomach, intestine, and 

 anus. 



8. PI YLUM BRYOZOA (Gr. bruon, moss; 

 zoon, animal). Moss animals and sea mats. 

 Small; aquatic, sessile, unsegmented; usu- 

 ally colonial; ciliated tentacles surround 

 mouth; U-shaped intestine with anus near 

 mouth; colonies often look superficially 

 like hydroid colonies. 



9. PHYLUM BRACHIOPODA (L. bracluum, arm; 

 Gv. podos,foo\). Lamp shells. Unsegmented 

 body covered with calcareous bivalve shell; 

 mouth is between two spiral, ciliated arms 

 which lie within shell; many fossil forms. 



10. PHYLUM ECHINODERMATA (Gr. ecllinOS, 



hedgehog; derma, skin). Sea lilies, starfish, 

 sea cucumbers, sea urchins. Marine; radi- 



