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.

Explanation:

Phylogenetic trees are built using shared derived traits to show evolutionary relationships. Julia knows mammals (platypus, bear, monkey) share a common ancestor with reptiles (lizard). To place the platypus correctly, a trait that links it to reptiles (showing its more basal position among mammals) is most helpful. The other options either describe shared mammal traits, irrelevant non-traits, or traits unrelated to the reptile-mammal relationship.

Answer:

The platypus lays eggs like a reptile.