Question

Three organisms have four shared characteristics. They all have a backbone and scales, lay eggs, and walk on land.

What can be determined based on this information alone?

They are members of different species.
They are members of the same species.
Their common ancestor has the same four shared characteristics.
Their common ancestor has none of the shared characteristics.

Answer 1

None of the four statements can be determined from that information alone.

- You cannot tell whether they are the same or different species just from shared traits.
- You cannot conclude their common ancestor had (or did not have) those traits from the fact that the living organisms share them — the traits might be inherited (homology) or might have evolved independently in different lineages (convergence/analogy).

To decide ancestry or species status you'd need additional data (morphology in more characters, genetic/phylogenetic analysis, fossil evidence, etc.).