66 The Living Things of the Earth unit i 



Class 2. Spiders (Araclmoidea): Two body parts and four pairs of legs. 

 Spider and scorpion. 



Class 3. Centipedes (Chilopoda): Segmented body. Each segment has one 

 pair of legs. 



Class 4. Millipedes (Diplopoda): Segmented body. Each segment has two 

 pairs of legs. 



Class 5. Crustaceans (Crustacea) : Five or more pairs of legs. Two pairs of 

 antennae. Live in salt water, fresh water or in damp earth. Lobster, crab, 

 barnacle. 

 Phylum III. Alollusks (Molhisca) : Soft-bodied invertebrates with a shell. In some 



the shell is internal and reduced in size. Live in fresh or salt water or on land. 



Snail, slug, clam, octopus. 

 Phylum IV. Echinoderms (Echinoderviata) : Radial symmetry, usually with five 



divisions. A spiny skin. Live only in salt water. Starfish, sea urchin, brittle star. 

 Phylum V. Segmented AVorms (Annelida) : Long cylindrical body with segments 



or rings. Thin moist skin; most without legs. Earthworm, clam worm, leech. 

 ?Hvi u,M \T Roundworms iN einatbclmmtbes) : Cylindrical body without seirments. 



Alany very small, causing disease and living within other animals. Hookworm, 



trichina worm. 

 Phy'lum VII. Flatworms (Platyhehuinthes) : Many live within bodies of other 



animals, causing disease. Planaria, tapeworm, liver fluke. 

 Phylum VIII. Coelenterates (Coelenterata) : Baglike with one opening. Tentacles 



and stinging cells. Some free-swimming, some attached, some forming colonies. 



Jellyfish, sea anemone, coral. Hydra. 

 Phylum IX. Sponge Animals (Porifera) : Baglike with many small openings through 



the sides. Attached. Some form colonies. Mostly salt water forms. Sponges. 

 Phylum X. Protozoans (Protozoa): Single-celled. Live in fresh or salt water or 



where it is moist. Some live within bodies of other animals and may cause 



disease. Some form shells and build up limestone rock. 



Questions 



1. How do the numbers of yertebrate and invertebrate species compare? 

 Cite an example of each of the nine phyla of invertebrates mentioned. 



2. What name is given to the most complex invertebrates? Give the two 

 characteristics in which they differ from all other animals. Into Y\hat 

 five groups (classes) do most of them fit? 



3. Describe the principal characteristics of the insects. Be sure to use 

 the correct terms. Describe the sense organs of a typical insect. How 

 do some insects make noises? 



4. Describe the life story of a buttcrflv, an insect that has complete 

 metamorphosis. How is incomplete metamorphosis different? 



5. Describe the insects with scaly wings. By what three characteristics 

 can you distinguish moths from butterflies? Name a moth of com- 

 mercial importance. 



6. Which common insects belong to the group of two-winged insects? 

 What name is given to the larval stage of the fly? 



7. Ijst tour relatives of the grasshopper. Describe body regions and ap- 

 pendages of the grasshopper. Discuss the importance of the grass- 

 hopper to man. 



