Stress prompts sexual reproduction in many unicellular protists. The diploid phase produces spores that grow into a haploid phase, which then produces gametes, two of which then fuse to form the diploid zygote, the first cell of the multicellular diploid phase. As many characteristics as possible are used in a phenetic analysis. Statistically-determined significant characters are given more weight or emphasis in phenetic analysis. Analogous structures are structures that are similar in appearance or function, but do not share a common evolutionary descent.
Homologous structures share a common evolutionary descent.
Features reflecting evolutionary relatedness are used in cladistics. The resulting cladogram shows the historical order in which evolutionary branches arose during the history of the group.