The current clarity of how the actual phylogenetic relationship among members of Eukarya is uncertain and hotly contested. Hypothetical relationships in this group are continually challenged by an ever-increasing body of data and analytical tools. While it is fairly certain that all eukaryotes share a common ancestor, early eukaryotes diverging from that ancestor appear to have undergone an extraordinary radiation (extremely rapid divergence) event. This series of divergences generated several groups of eukaryotes that are exceedingly dissimilar to each other (other than the presence of a nucleus, linear DNA and membrane-bound organelles. This dissimilarity has led evolutionary biologists to visualize the divergence of Eukarya equally into several group (some argue there are 5 groups, while others provide evidence for up to 10 groups). While it is known this artificial visualization of Euarya’s early divergences is clearly inaccurate, we are simply unsure how the major groups are related to each other.
In 2005, the International Society of Protistologists established a hypothetical division of Eukarya into six “supergroups” based on genetic analyses (Fig. 1). While this division is not without its critics, it represents “a majority vote” of our best understanding of higher order organization of Eukarya. Rather than attempting to resolve how these groups diverged from each other, you will be required to identify specific characteristics common (synapomorphic) to each “supergroup”, and investigate variability within specific groups.