^(52 The Earth and Its Inhabitants Change unit x 



Questions 



1. What is one important question that still remains to be answered in 

 regard to evolution? What was De Vries's contribution to this an- 

 swer? Define mutation. 



2. How do gene (or chromosome) changes differ in their effect on an 

 organism? Give two examples. 



3. Tell a few important facts about Charles Darwin's life. How did Dar- 

 win arrive at the conclusion that evolution had occurred? What im- 

 portant body of knowledge had not yet been discovered in Darwin's 

 day? What did Darwin call his theory to explain how species 

 originate? 



4. Who developed a theory of evolution at the same time Darwin did? 



5. Name the five steps in Darwin's theory of natural selection. Describe 

 or explain each step. What is one of the weaknesses in his theory? 



6. State Darwin's theory of evolution briefly without numbering the 

 steps. 



7. Tell how De Vries modified Darwin's explanation of the origin of 

 new species. Which of the steps of Darwin's theory did De Vries 

 accept? 



8. What is the name of Lamarck's theory? Describe the two parts of his 

 theory. Why do most biologists nowadays reject it? 



9. Describe two or more examples of protective adaptation. How does 

 De Vries's theory explain the presence of such adaptations? 



10. Sum up the idea of evolution and the best theory we have at the 

 present time for explaining how new species originate. 



Exercises 



1. List certain types of changes in the corn plant and the deer (or other 

 organism) that might weaken them. 



2. What kinds of changes in corn plants and deer might make it easier 

 for them to meet the competition of other organisms? 



3. Would you say that Darwin is known as one of the world's great sci- 

 entists because of his results, because of his methods, or both? Explain 

 fully by stating his results and describing his methods and his traits of 

 character. 



4. Prepare a list of your own observations of overproduction of or- 

 ganisms. Compare it with the lists prepared by your classmates. 



5. Name in order the steps of Darwin's theory of natural selection, and 

 explain each. 



6. Keeping in mind the five steps of Darwin's theory of natural selec- 

 tion state how De Vries would have explained the origin of the modern 

 species of horse from the Eohippus. Remember that this change is be- 

 lieved to have occurred in very many different steps. 



