learning objectives 6 Flashcards
What is a phylogeny/phylogenetic tree?
A phylogeny or phylogenetic tree shows the evolutionary history of a species or a group of species. It is a branching tree diagram that displays relationships among taxa, using data such as DNA, morphology, and fossils.
What does nested hierarchical categorization of organisms mean?
Nested hierarchy refers to the organization of organisms into progressively larger groups based on shared characteristics. It starts from a smaller group and moves to larger ones. This system is still in use today and is explained by Darwin’s idea that similarity often results from shared ancestry.
Why are phylogenetic trees considered hypotheses?
Phylogenetic trees are hypotheses because they represent proposed evolutionary relationships among a group of taxa, based on the best available data, but they are not definitive proofs.
What are the key components of a phylogenetic tree?
- Branch point: Represents the common ancestor of two lineages.
- Taxon (plural - taxa): A named level in the hierarchy.
- Root: The most recent common ancestor of all the taxa shown.
- Sister taxa: Share an immediate common ancestor and are each other’s closest relatives on the tree.
- Time: Flows from the root to the tips.
Define “lineage” and “character/trait.”
- Lineage: The entire history of a species traced back through time.
- Character/trait: Observable features of organisms, which can be morphological, behavioral, genetic, etc.
How is topology useful in reading phylogenetic trees?
Topology, the branching pattern of a tree, is informative about the relationships between taxa. The branch length may also be informative if a time scale is provided.
How are characters used to build a phylogenetic tree?
- Measure as many characters (traits) as possible.
- Score the characters to see which species have which traits.
- Mark character transitions on possible trees.
- Choose the most parsimonious tree.
What is the principle of parsimony in phylogenetics?
Parsimony is the principle that the tree with the fewest evolutionary changes (i.e., fewest character transitions) is most likely correct, based on the idea that change is rarer than staying the same.
How can phylogenetic trees be used to answer evolutionary questions?
hylogenetic trees can be used to determine evolutionary relationships, patterns of evolutionary change, divergence times, and to organize the totality of evolutionary history.
