Protoplasm 317 



SUMMARY 



All living things have certain activities, called functions. They 

 are : sensation, motion, respiration, food-taking, digestion, absorp- 

 tion, circulation, assimilation, excretion, and reproduction. 



All living matter consists of protoplasm. 



Protoplasm when examined under the compound microscope 

 appears to be a thin, nearly transparent fluid. It has the same ap- 

 pearance in all living things. 



Protoplasm has the same chemical composition and performs 

 the same functions in all living things. It consists of oxygen, 

 hydrogen, nitrogen, carbon, sulphur, and phosphorus. 



Nearly every organism contains lifeless as well as living mat- 

 ter. There is no protoplasm in lifeless matter. 



A tiny unit of protoplasm is called a cell. A typical plant or 

 animal cell consists of three essential parts: the nucleus, 

 a denser, rounded portion; the cytoplasm, the substance around 

 the nucleus ; and the cell wall. Cells may assume various irregular 

 forms. 



A living thing consists either of a single cell or of groups of 

 cells. 



Cells make up tissues. Tissues makt up organs. Organs are 

 essential parts of every higher living thing. This make-up of 

 cells, tissues, and organs is called structure. The cell is the unit 

 of both structure and function. 



Air, food, water, heat, and light are necessary to sustain life 

 in all living things. They make up what is known as environ- 

 ment. 



FACT AND THOUGHT QUESTIONS 



1. Describe the appearance of protoplasm. 



2. In what forms of plant and animal life can protoplasm be observed? 



3. Why does it hurt to pluck a hair from the head but not to cut it? 



4. Name some parts of the human body and of birds that contain no 

 protoplasm. 



5. Make a drawing of a typical cell, labeling each important part. 



6. Define (a) structure, (b) function. Give illustrations of each. 



7. Define cell, tissue, organ, organism. 



8. Why is a cell called the unit of both structure and function? 



9. What is meant by environment? 



