48 



FUNCTIONS OF LIVING THINGS 



Functions of the Parts of a Plant. We are all familiar with 

 the parts of a plant, the root, stem, leaves, flowers, and fruit. 

 But we may not know so much about their uses to the plant. Each 

 of these structures differs from every other 

 part, and each has a separate work or func 

 tion to perform for the plant. The root 

 holds the plant firmly in the ground and takes 

 in water and mineral matter from the soil; 

 the stem holds the leaves up to the light and 

 acts as a pathway for fluids between the root 

 and leaves; the leaves, under certain condi 

 tions, manufacture food for the plant and 

 breathe; the flowers form the fruits; the fruits 

 hold the seeds, which in turn hold young 

 plants which are capable of reproducing adult 

 plants of the same kind. 



The Functions of an Animal. As we 

 have already seen, the grasshopper has a 

 head, a jointed body composed of a middle 

 and a hind part, three pairs of jointed legs, 

 and two pairs of wings. Obviously, the 

 wings and legs are used for movement ; a 

 careful watching of the hind part of the 

 animal shows us that breathing movements 

 are taking place ; a bit of grass placed before it may be eaten, 

 the tiny black jaws biting little pieces out of the grass. If 

 disturbed, the insect hops away, and if we try to get it, it jumps 

 or flies away, evidently seeing us before we can grasp it. Hundreds 

 of little grasshoppers on the grass indicate that the grasshopper 

 can reproduce its own kind, but in other respects the animal seems 

 quite unlike the plant. The animal moves, breathes, feeds, and 

 has sensation, while apparently the plant does none of these. It 

 will be the purpose of later chapters to prove that the functions 

 of plants and animals are in many respects similar and that both 

 plants and animals breathe, feed, and reproduce. 



Organs. If we look carefully at the organ of a plant called a 

 leaf, we find that the materials of which it is composed do not ap- 



A weed notice the un 

 favorable environment. 



