554 ^^^ Earth and Its Inhabitants Change unit x 



Exercises 



1. In what ways are some of the vertebrate skeletons alike? In what 

 ways different? Study the skeletons of a frog, a reptile, and a cat. How 

 are the hind legs attached in each case? The ribs are attached to the verte- 

 brae; to what are thev attached at the other end? How does the breast- 

 bone of the bird differ from those of other vertebrates? What other re- 

 semblances and differences do you note in these skeletons? 



2. How do the embryos of vertebrates resemble each other? Use 

 museum preparations, models, charts, and pictures. In what kind of en- 

 vironment does each embryo spend the early part of its life? Which 

 structures appear first? Which structures change last? Among which 

 embryos do you find the greatest degree of resemblance? Is there greater 

 resemblance between embryos of animals that appeared on the earth in 

 closer succession? Sum up your observations. 



3. What is meant by precipitation? You can see a simple precipitation 

 by adding some silver nitrate solution to a test tube containing some 

 sodium chloride (table salt) solution. Suppose a rabbit had formed anti- 

 bodies against police dog serum so that a precipitate would be formed 

 when the blood of the two animals was mixed in a test tube. If you mixed 

 blood from the following animals with rabbit serum, which should theo- 

 retically form the largest precipitate, which next, and so on to the 

 smallest: spaniel, fox, wolf, cat, robin, crocodile, trout, and toad? 



4. Reread Problem 3, Unit I on classification, {a) Why are insects 

 and vertebrates classified in different phyla? {b) Why do fish and mam- 

 mals belong to different classes but the same phylum? {c) Why do the 

 horse and the cat belong to different orders but the same class? (d) Why 

 do the cat and the dog belong to different families but the same order? 



5. Can you show by diagram what you learned in Exercise 4? 



Further Activities in Biology 



1. By using college textbooks, find other examples of resemblances in 

 structure between vertebrates. Prepare a report. Make a list of resem- 

 blances among groups of invertebrates. 



2. There are many examples of vestigial organs in man. Look up this 

 subject in college textbooks. 



3. If you are good at using clay prepare a series of models showing 

 vertebrate embryos at various stages. If you use several colors you can 

 show similar organs and how they change. 



4. Prepare a report on the life of Linnaeus. Donald Culross Pcattie's 

 book, Gree?} Lajirels, is an interesting source of information. 



5. Draw a large map to show the distribution of certain types of plants 

 and animals. Which organisms will you choose? Why? 



