I offer a few examples for you and hope you can use them.
Look at a tree that has cow, dog, seal, giraffe, lion, bat, bird.
Now that would be a valid tree of currently living species.
Look at a tree that has cow, dog, seal, giraffe, lion, bat. That would be a valid tree of mammals but the bird would lack features that allow it to be called a mammal.
Phylogenetic trees are not just random associations. They are based on the actual physical evidence that is found in each item in the list.
Even critters as different as a bat, a seal, a lion and a giraffe share common features that allow them to be classified under the broad tree called mammals.