If the hypothesis of evolution is true, the species that lived in the remote past must be different from the species alive today.
Natural selection can be operative only if more offspring are born than survive.
If the hypothesis of evolution is true, there must be differences between the offspring that survive and reproduce and those that do not. If the members of a taxonomic unit, such as the phylum chordata, share a common ancestry, that fact should be reflected in their structure. If evolutionary divergence is the basis of organic diversity, that fact should be reflected in the system of classification. If there is a unity of life based on descent from a common ancestor, this should be reflected in the structure of cells. This page is suitable for direct copying off the internet.