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Questions and Answers
What is the term for a lineage that evolved early from the root and remains unbranched?
What is the term for a lineage that evolved early from the root and remains unbranched?
What is the common ancestor of Taxon D, E, and F represented by in the phylogenetic tree?
What is the common ancestor of Taxon D, E, and F represented by in the phylogenetic tree?
What is the term for a characteristic that is shared by two or more taxa, but is not present in their common ancestor?
What is the term for a characteristic that is shared by two or more taxa, but is not present in their common ancestor?
What is the term for a feature that has changed from an ancestral state to a derived state?
What is the term for a feature that has changed from an ancestral state to a derived state?
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What is the term for a pattern of divergence where multiple taxa emerge from a single branch point?
What is the term for a pattern of divergence where multiple taxa emerge from a single branch point?
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What is the term for the study of the history of the evolution of a group of organisms?
What is the term for the study of the history of the evolution of a group of organisms?
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What is the primary tenet of phylogenetic systematics?
What is the primary tenet of phylogenetic systematics?
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What is the basis of the relationship between taxa in phylogenetic systematics?
What is the basis of the relationship between taxa in phylogenetic systematics?
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What do molecular homologies, such as DNA and RNA sequences, indicate?
What do molecular homologies, such as DNA and RNA sequences, indicate?
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What is a clade in a phylogenetic tree?
What is a clade in a phylogenetic tree?
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What is a paraphyletic clade?
What is a paraphyletic clade?
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What is the purpose of a cladogram?
What is the purpose of a cladogram?
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What is the primary characteristic of a polyphyletic clade?
What is the primary characteristic of a polyphyletic clade?
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What is the purpose of identifying homologies in constructing a cladogram?
What is the purpose of identifying homologies in constructing a cladogram?
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What is the role of an outgroup in constructing a cladogram?
What is the role of an outgroup in constructing a cladogram?
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Why is it essential to select an appropriate ingroup when constructing a cladogram?
Why is it essential to select an appropriate ingroup when constructing a cladogram?
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What is the purpose of constructing a character table in cladogram construction?
What is the purpose of constructing a character table in cladogram construction?
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Study Notes
Reading a Phylogenetic Tree
- A basal taxon is the oldest and most primitive, representing the earliest lineage that evolved from the root and remains unbranched.
- Sister taxa are two lineages that stem from the same branch point, sharing a common ancestor.
- A polytomy is an unresolved pattern of divergence, where multiple branches emerge from a single point.
- Branch points represent the common ancestor of two or more species.
Key Concepts
- Apomorphic features are derived from an ancestral state, representing evolutionary change.
- An autapomorphy is a unique feature of a single taxon.
- Synapomorphies are shared characteristics among multiple taxa, indicating evolutionary relationships.
- Polytomous taxa form unresolved patterns of divergence.
Phylogenetic Trees
- Represent a hypothesis about evolutionary relationships.
- Each branch point represents the divergence of two species.
- Tree branches can be rotated around a branch point without changing the evolutionary relationships.
- A rooted tree includes a branch to represent the last common ancestor of all taxa in the tree.
- A basal taxon diverges early in the history of a group and originates near the common ancestor group.
Primary Tenet of Phylogenetic Systematics
- All forms of life share a common ancestor.
- Taxa that share a common ancestor more recent in time are more closely related to one another than they are to a taxon whose common ancestor is further back in time.
Molecular Homologies
- DNA and RNA sequences of nucleic acids provide evidence for evolutionary relationships.
- Each change in a nucleic acid represents one evolutionary event.
- More events indicate a more distant relationship, while fewer events indicate a closer relationship.
Cladograms and Clades
- A cladogram is a type of phylogenetic tree.
- A clade is a group of species that includes a common ancestor and all its descendants.
- Monophyletic clades consist of a common ancestor and all its descendants, meeting the cladistic criterion.
- Paraphyletic clades consist of an ancestor and some but not all of the descendants, failing the cladistic criterion.
- Polyphyletic clades consist of various species with different ancestors, lacking a common ancestor.
Constructing Cladograms
- Identify homologies, or shared characteristics derived from one ancestor.
- Select species for the ingroup and outgroup.
- Select an outgroup with no shared derived characters but shared primitive characters.
- Construct a character table and tabulate the data.
- Construct a cladogram based on the number of shared characters.
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Description
Learn to read and understand phylogenetic trees, including concepts like basal taxon, sister taxa, polytomy, and branch points. Discover how to identify ancestral and derived states and more!
