Question

Julia is trying to place a duckbilled platypus, lizard, bear, and monkey on a phylogenetic tree. She learns that the duckbilled playpus, bear, and monkey are classified as mammals. She also learns that mammals share a common ancestor with reptiles. What additional piece of information will be most helpful to Julia to properly build her phylogenetic tree?

Answer 1

To properly build the phylogenetic tree, Julia needs information that can connect any of mentioned mammals (bear and monkey) to reptiles. And that could be only the fact that a duckbilled platypus lays eggs similarly like reptiles. So, the platypus is a mammal and relationship with bear and monkey in that way exist, but laying eggs is not characteristic for other mammals.