Essential Knowledge 1.B.2

Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested.

Phylogenetic trees and cladograms can represent traits that are either derived or lost due to evolution. Illustrative examples include:

• Number of heart chambers in animals
• Opposable thumbs
• Absence of legs in some sea mammals.

Phylogenetic trees and cladograms illustrate speciation that has occurred, in that relatedness of any two groups on the three is shown by how recently two groups had a common ancestor.

Phylogenetic trees and cladograms can be constructed from morphological similarities of living or fossil species, and from DNA and protein sequence similarities, by employing computer programs that have sophisticated ways of measuring and representing relatedness among organisms.

Phylogenetic trees and cladograms are dynamic (i.e., phylogenetic trees and cladograms are constantly being revised), based on the biological data used, new mathematical and computational ideas, and current and emerging knowledge.

Students should be able to:

LO 1.17 Pose scientific questions about a group of organisms whose relatedness is described by a phylogenetic tree or cladogram in order to (1) identify shared characteristics, (2) make inferences about the evolutionary history of the group, and (3) identify character data that could extend or improve the phylogenetic tree.

LO 1.18 Evaluate evidence provided by a data set in conjunction with a phylogenetic tree or a simple cladogram to determine evolutionary history and speciation.

LO 1.19 Create a phylogenetic tree or simple cladogram that correctly represents evolutionary history and speciation from a provided data set.