QUESTIONS 423 



Animals take their energy indirectly from the foods pre- 

 pared by green plants or by other animals. They are 

 usually classed as invertebrate and vertebrate. The lowest 

 form of invertebrate is the protozoon. Worms and insects 

 are other forms of invertebrates, the importance of which is 

 seldom realized. 



The bony skeleton in the higher forms of vertebrates 

 consists of a backbone, skull, ribs, and appendages. In the 

 skull is the brain, connected with the various parts of the 

 body by nerves. Vertebrates breathe by receiving air 

 through the windpipe into the lungs. This is done by the 

 muscles of the chest and the diaphragm. The lungs purify 

 the blood, which circulates from the heart through the 

 arteries and capillaries and returns through the veins. 



The five senses are taste, smell, touch, sight, and hearing. 

 These sensations are carried to the brain by the nerves, 

 which come from the nose, the mouth, the skin, the eye, and 

 the ear, respectively. Sound is a wave motion in a material 

 medium. The ear is a sound transmitter, which conveys 

 sound vibrations by way of the auditory nerve to the brain. 



For all the activities of body and brain food is required. 

 As the food passes through the alimentary canal, various 

 juices are mixed with it and certain parts of it are digested 

 and absorbed into the circulatory system of the body. 



QUESTIONS 



What are the three parts into which many plants can be readily 

 separated ? 



In what three respects are plants and animals alike? 



Of what use to the plant are the roots ? Why are roots necessary 

 to the higher plants ? 



Describe some different kinds of stems that you have seen and 

 explain their adaptability or lack of adaptability for making 

 the best of the conditions where they were. 



