CHAPTER 9 • HOW DO LIVING THINGS 



GET AND MANAGE THEIR FOOD? 



1 What happens to food after it is eaten? 



2 How does the food which we place in the mouth and swallow 



get to the other organs of the body? 



3 How is it that grass is suitable for the buffalo, flesh for the tiger, 



and wood for the termite? 



4 Could meat-eating animals thrive if they were fed exclusively 



on vegetable matter? Or could cattle live on meat? 



5 How do growing plants get at the food stored in seeds, roots, or 



underground stems? 



6 How can some animals eat their meal and chew it later? 



7 What connection is there between body build and feeding 



habits ? 



8 How are the activities of animals related to food-getting? 



9 Why are some kinds of food more easily digested than others? 



Some animals eat but a limited number of things. Others, like man, 

 feed on a great variety. Species that feed on meat alone differ in structure 

 and in behavior from those that feed on grass alone, for example. The 

 talons and beak of a hawk, the rough, grasping tongue of the ox, the pierc- 

 ing mouth of a mosquito, and the biting mandibles of the grasshopper all 

 seem to be especially related to getting particular kinds of food. In fact, the 

 whole nature of an animal seems closely connected with his eating habits. 

 Do the digestive systems of different animals vary, as the food-getting 

 habits do? 



How Do Plants Manage the Food They Make? 



Digestion^ The sugars which are first produced during photosynthesis 

 are in many plants later changed into starches. Most of our common plants, 

 however, produce starch in their leaves. Now starches are colloids — that is, 

 they are like glue and cannot diffuse through cell walls — whereas sugars are 

 crystalloids, or like crystals, and can diffuse through a membrane. Experi- 

 ments show that in both animals and plants starches are changed into sugars. 



When grains and other starch-bearing seeds germinate, the starch slowly 

 changes into sugar. We can wash out of such sprouting seeds a substance 

 called diastase. And we can show that in the presence of water, diastase 

 converts starch into sugar. This process is called digestion. 



iSee Nos. 1, 2 and 3, pp. 182-183. 

 163 



