What do a tree and a house fly have in common?

a tree and a horse fly have several thing in common 1. they live on this earth 2. they are both living 3. they need energy to survive 4. they are both multi-cellular 5. and both need water. *EDIT* Those traits they share in common with a majority of all living things, what makes the relationship between the fly and the tree unique, is that they both have exoskeletons.