1. _______ are traces of ancient organisms from which we can infer the ancestry and relationship of living forms.

2. Homologous structures may perform______functions door species in different environment, or it may have the___________functions for species in different origin but different functions.

3._______ structures have similar functions but different origin.

4. Patterns in animal development suggest that some organisms may have______ ancestor.

5. The ______ amino acid differences there are, the closer the relationship of organisms.​