SURVEY QUESTIONS 



Can you distinguish between invertebrate and vertebrate animals? 

 How many kinds of insects can you recognize? How many mollusks 

 live in your locality ? How many kinds of fishes, reptiles, and birds can 

 you identify ? How many mammals can you identify ? What is a fossil ? 



UNIT VIII 



HOW DO WE CLASSIFY ANIMALS? 



Preview. In the classification of animals, as well as of plants, 

 there is one underlying principle which is used to show relationships. 

 Living things which have similar structures or organs in similar 

 parts of their bodies are almost certainly related to each other. 

 Where structures are similar and are found in corresponding 

 positions, they are said to be homologous. For example, the wing 

 of a bat, the wing of a bird, the foreflipper of a dolphin, the fore- 

 leg of a dog, and the arm of a man are homologous structures and 

 show that these animals are, in a way, related to one another. On 



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