Phylogeny quiz #1 Flashcards
Phylogeny quiz #1
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What is a phylogenetic tree and what information does it convey about organisms?
A phylogenetic tree is a branching diagram that shows the evolutionary relationships among organisms, illustrating how groups are related through common ancestors. How do you determine which organisms are most closely related on a phylogenetic tree?
Organisms are most closely related if they share a recent common ancestor, which is found by tracing their branches back to the nearest connecting node. What is the difference between homology and analogy in evolutionary biology?
Homology refers to similarities due to shared ancestry, while analogy refers to similarities that arise from convergent evolution, not common ancestry. Define the terms 'monophyletic group', 'paraphyletic group', and 'polyphyletic group' in cladistics.
A monophyletic group (clade) includes a common ancestor and all its descendants; a paraphyletic group includes a common ancestor and some, but not all, descendants; a polyphyletic group includes organisms from different ancestors. What is a synapomorphy and why is it important in phylogenetic analysis?
A synapomorphy is a shared derived trait found in two or more taxa and their most recent common ancestor, helping to define evolutionary relationships. What is the function of an outgroup in phylogenetic studies?
An outgroup is a taxon outside the group of interest, used for comparison to help determine which traits are ancestral or derived within the ingroup. What do the terms 'branch', 'node', 'root', and 'sister taxa' mean in the context of a phylogenetic tree?
A branch represents a lineage, a node is a common ancestor where lineages split, the root is the most recent common ancestor of all taxa in the tree, and sister taxa are two groups that share an immediate common ancestor. What is a polytomy in a phylogenetic tree, and what does it indicate?
A polytomy is a node with more than two branches, indicating either simultaneous divergence of multiple lineages or uncertainty about their exact relationships. How can the same phylogenetic relationships be represented by trees with different shapes or orientations?
Phylogenetic trees can be drawn in various shapes or orientations (e.g., rotated, circular, or with different branch arrangements), but as long as the branching order and common ancestors are preserved, the relationships remain the same. What are the possible meanings of branch length in a phylogenetic tree, and how should you interpret them?
Branch length can mean nothing (just showing relationships), represent time (with a timeline), or indicate the amount of evolutionary change (number of mutations); unless specified, assume branch length has no meaning.
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