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Ch. 29 - Plant Diversity I: How Plants Colonized Land
Chapter 29, Problem 7

EVOLUTION CONNECTION DRAW IT Draw a phylogenetic tree that represents our current understanding of evolutionary relationships between a moss, a gymnosperm, a lycophyte, and a fern. Use a charophyte alga as the outgroup. (See Figure 26.5 to review phylogenetic trees.) Label each branch point of the phylogeny with at least one derived character unique to the clade descended from the common ancestor represented by the branch point.

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Identify the outgroup, which is the charophyte alga, and place it at the base of the phylogenetic tree.
Determine the first branch point after the outgroup, representing the divergence of mosses. Label this branch point with a derived character unique to mosses, such as the presence of a cuticle.
Identify the next branch point, representing the divergence of lycophytes. Label this branch point with a derived character unique to lycophytes, such as the presence of vascular tissue.
Determine the next branch point, representing the divergence of ferns. Label this branch point with a derived character unique to ferns, such as the presence of true leaves (megaphylls).
Identify the final branch point, representing the divergence of gymnosperms. Label this branch point with a derived character unique to gymnosperms, such as the presence of seeds.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Phylogenetic Tree

A phylogenetic tree is a diagram that represents evolutionary relationships among various biological species based on their shared characteristics and genetic information. Each branch point, or node, indicates a common ancestor from which descendant species diverged. The tree helps visualize the evolutionary history and the relative timing of species' divergence.
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Derived Characters

Derived characters are traits that are present in a clade but absent in the last common ancestor of that clade. These traits are crucial for defining evolutionary relationships and are used to distinguish between different groups in a phylogenetic tree. Identifying derived characters helps clarify how species are related and the evolutionary adaptations that have occurred over time.
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Shared Derived Characters

Outgroup Comparison

An outgroup is a species or group of species that is closely related to the ingroup (the main group being studied) but not part of it. In phylogenetic analysis, outgroups are used to help determine the direction of evolutionary changes and to root the tree. By comparing the ingroup to the outgroup, researchers can identify which traits are ancestral and which are derived.
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Ingroups, Outgroups, & the Character Matrix