Question

Explain how scientists can determine relationships

Answer 1

When animals first crawled onto land, one of the greatest obstacles they had to contend with was figuring out how to breathe. No longer bathed in oxygen-rich marine waters, their gills would surely have dried out. Scientists have analyzed fossils from 500-million-year-old rocks that show one way these early pioneers may have dealt with this problem--the first terrestrial animals carried a shell on their backs.