6 BIOLOGY FOR BEGINNERS 



Respiration. Another point in which our two examples are alike 

 is that they both breathe. If we keep either one in an air-tight 

 box it will die. The cat breathes by means of its lungs and it is 

 easy to see the muscular movements involved. The leaves of the 

 plant breathe too, although our eyes cannot detect the way in 

 which this is done. The process of breathing is called respiration 

 in both cases. 



Excretion. Both cat and geranium use the food that they 

 assimilate to build up their bodies or to give them energy, and 

 both throw off from their bodies unused and changed food materials 

 by a process called excretion. The animal does this by means of 

 the lungs, skin, intestines and kidneys; the plant by means of 

 the leaves. 



Motion. Another way in which all living things are alike is in 

 the power of motion. It is easy to see the cat move, but few observe 

 how the geranium turns its leaves to the light and its roots to the 

 water. Though animals usually have greater freedom of motion, 

 plants do not lack it altogether. 



Sensation. In a general way, all plants and animals have the 

 power of responding to touch, heat, light, and other forces outside 

 of themselves. This is sensation, and may vary in its expression, 

 from the mere turning of leaves toward light to the delicate opera- 

 tion of a wonderful sense organ like the human eye. 



Reproduction. Both plants and animals reproduce others like 

 themselves. Kittens are born and grow to be cats, and the plant 

 bears seeds which will produce other plants like itself. By this 

 wonderful provision of nature, although all organic things die, 

 others like them are left to take their places. The processes of 

 reproduction and nutrition are the two most important charac- 

 teristics of all living things. 



Likeness of all Living (Organic) Things. The cat before the 

 fire and the geranium on the window sill, though apparently 

 different, are really alike in all of the necessary processes of life. 

 It is, therefore, possible and easy to study plants and animals 

 together. Biology is not merely botany plus zoology, but a study 

 of the life processes of all living things. 



