Based on the phylogenetic tree in Figure 28.5, which of the following statements is correct? (A)Excavata and SAR form a sister group. (B)The most recent common ancestor of SAR is older than that of Unikonta. (C)The most basal (first to diverge) eukaryotic supergroup cannot be determined. (D)Excavata is the most basal eukaryotic supergroup.

Verified step by step guidance

1. Analyze the phylogenetic tree to understand the relationships between the groups.
2. Identify the position of Excavata, SAR, and Unikonta on the tree.
3. Determine the most recent common ancestors for SAR and Unikonta.
4. Check if the tree indicates which eukaryotic supergroup diverged first.
5. Compare the statements with the tree to find the correct one.

Key Concepts

Phylogenetic Tree

A phylogenetic tree is a diagram that represents evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics. It illustrates how species are related through common ancestry, with branches indicating divergence points. Understanding how to read and interpret these trees is crucial for analyzing evolutionary relationships and determining the correct statements about groups like Excavata, SAR, and Unikonta.

Eukaryotic Supergroups

Eukaryotic supergroups are major lineages within the domain Eukarya, which includes all organisms with complex cells. The main supergroups are Excavata, SAR (Stramenopiles, Alveolates, Rhizarians), Archaeplastida, and Unikonta. Each supergroup encompasses a diverse range of organisms, and understanding their evolutionary relationships helps in determining the most basal groups and their common ancestors.

Sister Groups

Sister groups are pairs of taxa that are more closely related to each other than to any other group. In a phylogenetic tree, sister groups share a common ancestor that is not shared with any other group. Identifying sister groups is essential for understanding evolutionary relationships and can help clarify statements regarding the relative ages of common ancestors among different eukaryotic supergroups.