Lecture 7: Phylogenies Flashcards
What is a phylogenetic tree?
A phylogeny is an evolutionary history of a species or group of species
Define these parts of a phylogeny
- Branch
- Node
- Tip
- Outgroup
- Root
- Polytomy
- Branch: Lines of the phylogeny
- Node: Connecting points (a hypothesized common ancestor)
- Tip: Endpoints of the trees that represent living species
- Outgroup: A taxon that split early from the other taxa
- Root: Denotes the oldest part of the tree
- Polytomy: A node that divides into more than one branch
What is a homology? How is this different from homoplasy?
Dolphins and icthyosaurs
A homology is a similarity due to common ancestry.
A homoplasy is a similary NOT due to common ancestry. This
Streamlined bodies, flippers, and dorsal fins are adaptations that help any aquatic species. Came up from convergent evolution
What is a monophyletic group?
A monophyletic group is a set of taxa on a phylogeny that includes an ancestral species and all of its descendents ONLY.
What is a synapomorphy?
A synapomorphy is a trait that is found in a set of taxa that was probably present int heir most recent common ancestor but not in more distant species.
What is a molecular phylogeny and how is it used? What is the most common gene sequence that is compared?
A molecular phylogeny is determined by comparing DNA sequences between organisms. The most common sequence is that of ribosomal DNA, since all organisms make proteins they all have ribosomes.
