EXERCISE 133 



In animals that have two or more similar parts (or pairs of structures) arranged from front to rear, 

 such as vertebrae, rings of a worm, paired appendages, etc., these parts are considered to be homologous, 

 or of identical origin. Among backboned animals and among arthropods (insects, crustaceans, spiders, 

 etc.), where the appendages are numerous, it is possible to find species that show one or more special 

 modifications of structure related to protection. 



In some suitable specimen (for example, grasshopper, crayfish, crab, beetle, frog, cat, etc.) study the 

 homologous structures, to find in what ways any of them show adaptation to protection of the individual. 



Record your findings, using diagrams to bring out the differences between the protecting structures 

 and the homologous structures that are not protecting. 



[146] 



