Question

Julia is trying to place a duckbilled platypus, lizard, bear, and monkey on a phylogenetic tree. She learns that the duckbilled platypus, bear, and monkey are classified as mammals. She also learns that mammals share a common ancestor with reptiles. Which additional piece of information will be most helpful to Julia to properly build her phylogenetic tree?
The platypus has fur like other mammals.
The platypus does not have feathers like a bird.
The platypus lays eggs like a reptile.
The platypus does not have fins like a fish.

Answer 1

"The platypus lays eggs like a reptile."

Why: that trait links the platypus to reptiles in retaining the ancestral egg-laying condition and indicates monotremes branched off before the evolution of live birth in other mammals. The fur fact just repeats that it's a mammal; the egg-laying trait is what helps resolve its position on the tree.