Podcast
Questions and Answers
Which type of taxon includes an ancestral species and only some of its descendants?
Which type of taxon includes an ancestral species and only some of its descendants?
What is a key characteristic of a polyphyletic taxon?
What is a key characteristic of a polyphyletic taxon?
Why is it important for contemporary systematics to identify monophyletic groups as taxa?
Why is it important for contemporary systematics to identify monophyletic groups as taxa?
What distinguishes a polyphyletic taxon from a paraphyletic taxon?
What distinguishes a polyphyletic taxon from a paraphyletic taxon?
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In what circumstances have biologists historically named non-monophyletic taxa?
In what circumstances have biologists historically named non-monophyletic taxa?
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What is a common feature of a monophyletic taxon?
What is a common feature of a monophyletic taxon?
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Why is the Felidae considered monophyletic?
Why is the Felidae considered monophyletic?
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What does a monophyletic taxon include?
What does a monophyletic taxon include?
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Why are gorillas and chimpanzees considered sister taxa?
Why are gorillas and chimpanzees considered sister taxa?
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Why are orangutans classified in the Hominoidae group?
Why are orangutans classified in the Hominoidae group?
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What does a node represent in a phylogenetic tree?
What does a node represent in a phylogenetic tree?
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Why are New World monkeys classified separately from Old World monkeys in the anthropoid group?
Why are New World monkeys classified separately from Old World monkeys in the anthropoid group?
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Which system is proposed for identifying and naming organisms based on unique synapomorphies?
Which system is proposed for identifying and naming organisms based on unique synapomorphies?
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Why are shared ancestral character states like a vertebral column and four legs not useful in defining the mammal clade?
Why are shared ancestral character states like a vertebral column and four legs not useful in defining the mammal clade?
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What type of evolutionary lineages and taxa are described using cladistic analyses?
What type of evolutionary lineages and taxa are described using cladistic analyses?
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How are the results of a cladistic analysis typically presented?
How are the results of a cladistic analysis typically presented?
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What does each branch in a phylogenetic tree portray?
What does each branch in a phylogenetic tree portray?
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What is the purpose of identifying an outgroup in phylogenetic studies?
What is the purpose of identifying an outgroup in phylogenetic studies?
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Study Notes
Monophyletic Taxa
- A monophyletic taxon includes all descendants of a common ancestor and is defined at every level of the taxonomic hierarchy.
- Example: Felidae (family-level taxon) includes all cat species, which are descendants of a common ancestor that lived 25 million years ago.
Monophyletic vs. Polyphyletic vs. Paraphyletic Taxa
- Monophyletic taxon: an ancestor and all of its descendants are included.
- Polyphyletic taxon: includes species from different evolutionary lineages, and the most recent common ancestor is not included.
- Paraphyletic taxon: includes an ancestral species and only some of its descendants, excluding some descendants of the common ancestor.
Defining Taxa in a Classification
- A major goal of contemporary systematics is to identify taxa that are monophyletic groups, which are descendants of one common ancestor.
- Biologists have not always defined strictly monophyletic taxa, sometimes due to missing data or convenience.
PhyloCode and Cladistic Analysis
- PhyloCode is a strictly phylogenetic system that identifies and names clades instead of using traditional taxonomic categories.
- Cladistic analysis is used to describe evolutionary lineages and taxa, presenting results in a phylogenetic tree that illustrates the hypothesized sequence of evolutionary branchings.
- Every branch in the tree portrays a strictly monophyletic group, and a common ancestor is hypothesized at each node.
Identifying an Optimal Phylogenetic Tree
- Systematists use several techniques to identify an optimal phylogenetic tree, including collecting data on hundreds of characters in dozens of species.
- Researchers identify a suitable outgroup to analyze the evolutionary relationships between organisms.
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Description
Explore the concept of monophyletic taxa in the taxonomic hierarchy using the example of Felidae family and Animalia kingdom. Understand how monophyletic groups are small, complete branches on the Tree of Life.
