PROBLEM I. The Kijids of An'mials 



groups. This system is called classifica- 

 tion. You first studied the mammals, the 

 animals A\'hich are most closely related 

 to you, yourself. Then you spent some 

 time with the birds, the reptiles, the am- 

 phibians, and the fish. The fish were the 

 last vertebrates you studied. All of these 

 had a backbone just as you have. You 

 then met the invertebrates, the animals 

 without backbones. It took a long time to 

 get acquainted with man's insect friends 

 and enemies and the other, less familiar, 

 arthropods. From then on you saw mostly 

 water forms: the shelled mollusks, the 

 spiny echinoderms; the worms, some of 

 which burrow in the moist earth; the 

 coelenterates whose beautiful colors and 

 unusual shapes remind one of flowers; 

 and the sponges. 



of the Earth 65 



There were still many animals for you 

 to see, but in order to see them it was 

 necessary for you to equip yourself with 

 a microscope. Then suddenly a whole 

 new world opened itself out to you: the 

 world of Protozoa. A glimpse at these 

 and you finished your study of the ani- 

 mal kingdom. 



You saw only very few of the almost 

 one million difl^erent kinds of animals. If 

 you were to examine each living species 

 for only one minute and if you were to 

 keep at it day and night, it w^ould take 

 you almost two years to review the ani- 

 mal kingdom. Study of the summary be- 

 low will give you a scientific view of the 

 journey you have just completed. 



Our attention must now be turned to 

 the plant kingdom. 



Summary 



This simpHfied table will help you review the animal kingdom. 



Phylum I. Chordates (Chordata): The name is from the word "cord" and refers 

 not to the spinal cord but to the notochord which is present in adults of some 

 subphyla and which develops into the backbone of the vertebrates. Most zoolo- 

 gists recognize four small subphyla other than the vertebrates we have studied. 



SuBPHYLUM. Vertebrates (Vertebrata) 



Class i. Mammals (Ma?mnalia) : Hair covering. Feed young on milk from 



mammary glands. 

 Class 2. Birds (Aves) : Feathers. 



Class 3. Reptiles (Reptilia): Dry scaly skin. Breathe by means of lungs. 

 Class 4. Amphibians (Amphibia) : Thin, moist skin. All spend first part of 



life in water; most later hve on land. 

 Class 5. Fish (Pisces) : Scaly skins that are moist. Breathe by means of gills. 



The sharks discussed on page 32 along with certain other animals make 

 up another small class. All the other phyla are invertebrate phyla. We 

 studied the following: 



Phylum II. Arthropods (Arthropoda) : A hard outside covering. Segmented bodies 



and jointed legs. 



Class i. Insects (Insecta): Head, thorax, and abdomen with three pairs of 

 legs on thorax. Complete or incomplete metamorphosis in their develop- 

 ment. May live on land or in water. Grasshopper and butterfly. 



