What clues indicate that dogs are more closely related to cats than to lizards?  

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pacorz eNotes educator| Certified Educator

While dogs, cats, and lizards are all related in that they are all vertebrate animals, dogs and cats have a number of traits in common that they do not share with lizards. Generally, the more traits two species share, the more closely they are considered to be related. In this case, traits that both dogs and cats share but lizards do not would include:

A) Warm bloodedness - cats and dogs are homeotherms, while lizards are poikilotherms

B) Body hair - cats and dogs have fur, while lizards have scales

c) Placental pregnancy and live birth - cats and dogs bear live young, while lizards lay eggs

D) Parental care of young - cats and dogs care for the newborns and feed them via mammary glands, while most species of lizards simply lay their eggs and leave them

In sum, both cats and dogs are mammals, while lizards are reptiles.

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