18. The geological timescale was first developed using the fossil record, but this provided only a system of relative dating; absolute dates weren't established until the discovery of:radioactive decay.isotopes.sedimentary rocks.fossil series.
19. The diagram below depicts three phylogenetic trees. Which of the three show the same sister group relationships among groups A, B, and C?
20. Phylogenetic trees can be built using:
21. The phylogeny below represents a hypothesis for the evolutionary relationships among major groups of plants. If it is correct, in what order should we predict to find the fossils of these groups, in order from oldest to youngest?<br /><img src="[~]/resources/chapter_23/q136-1.jpg" width="384" height="405" />ferns, moss group, conifer group, flower groupferns, conifer group, moss group, flower group