A phylogenetic tree is shown for the three domains of life (Eukarya, Archaea, and Bacteria). The tree branches in two directions from the first point, labeled Common ancestor of all life. One branch leads in the direction of Eukarya and Archaea, and the other branch leads to Bacteria. The branch leading to Eukarya and Archaea divide, one branch leading to each domain. The branch leading to Eukarya divides into four branches. One leads to Euglenozoans, and the other three lead to branching points. The first leads to Forams in one direction, and another branching point in the other that leads to Diatoms and Ciliates. The second branching point leads to Red algae in one direction, and a branching point that leads to green algae and land plants in the other direction. The third branching point leads to amoebas in one direction, and a branching point that leads to fungi and animals in the other direction. Land plants, Fungi and Animals are all highlighted.
Examine the figure. If you were a graduate student trying to develop a thesis project that would resolve polytomies, which of the following groups would you study?
A) animals and fungi
B) euglenozoans, euryarcheotes, and gram-positive bacteria
C) forams, red algae, and amoebas
D) red algae, green algae, and cyanobacteria

Question

A phylogenetic tree is shown for the three domains of life (Eukarya, Archaea, and Bacteria). The tree branches in two directions from the first point, labeled Common ancestor of all life. One branch leads in the direction of Eukarya and Archaea, and the other branch leads to Bacteria. The branch leading to Eukarya and Archaea divide, one branch leading to each domain. The branch leading to Eukarya divides into four branches. One leads to Euglenozoans, and the other three lead to branching points. The first leads to Forams in one direction, and another branching point in the other that leads to Diatoms and Ciliates. The second branching point leads to Red algae in one direction, and a branching point that leads to green algae and land plants in the other direction. The third branching point leads to amoebas in one direction, and a branching point that leads to fungi and animals in the other direction. Land plants, Fungi and Animals are all highlighted.
Examine the figure. If you were a graduate student trying to develop a thesis project that would resolve polytomies, which of the following groups would you study?
A) animals and fungi 
B) euglenozoans, euryarcheotes, and gram-positive bacteria 
C) forams, red algae, and amoebas 
D) red algae, green algae, and cyanobacteria

Quizplus · Accepted Answer

Polytomies are unresolved branching points in evolutionary trees. In the figure, the branch leading to Forams, Red algae, and Amoebas has multiple branching points, suggesting unresolved relationships. Therefore, studying these groups may help resolve these polytomies. Animals and fungi (choice A) are already well-established groups with resolved relationships, and euglenozoans, euryarcheotes, and gram-positive bacteria (choice B) are not involved in the unresolved branching point of the tree. Red algae, green algae, and cyanobacteria (choice D) are part of a resolved branching point and are not involved in unresolved relationships.

A Phylogenetic Tree Is Shown for the Three Domains of Life