52 TYPICAL ANIMAL CELL 



Simple animals are very similar to simple plants in structure and 

 function. The main differences are that animals have the function 

 of locomotion, and are adapted to perform this function. Very few 

 plants have the power of locomotion. Green plants manufacture 

 their own food by means of their chlorophyll, and do not have to 

 seek food as most animals do. In addition to the plasma mem- 

 brane, there is a protective wall in the plant cells made of a non- 

 living material, cellulose. This is missing in animal cells. Amoebas 

 are bounded by the plasma membrane only. 



A cell, either plant or animal, has been shown to be a tiny mass 

 of protoplasm, generally having a nucleus and having a boundary, 

 a cell wall, or an animal membrane. The cell theory as first stated 

 by Schleiden and Schwann has been checked by many scientists 

 over a long period of years. To-day, it is no longer considered 

 a theory but is accepted, somewhat modified, as a doctrine. 

 Among other things this theory states that the cell is the unit of 

 structure and of function and that all plants and animals are 

 made up of cells and cell products. 



QUESTIONS 



1. Name the forms of energy needed by the amoeba or Para- 

 mecium. 



2. Classify the physiological functions into nutritive, adaptive, and 

 reproductive. Give the functions of each class. 



3. Why is digestion necessary in animals ; in plants ? 



4. What is the main difference in the nutrition of a plant and 

 animal ? 



5. Discuss some positive and negative examples of tropisms. 



6. In outline form, compare the structure and function of a one- 

 celled plant and a one-celled animal. 



7. Discuss the importance of chlorophyll to animals. 



8. What is meant by physiological division of labor and speciali- 

 zation of protoplasm ? 



9. Make a library report on the economic importance of protozoa. 



