Lecture 39 Flashcards
What is a phylogenetic tree?
A hypothesis of evolutionary relationships where more closely related taxa are clustered
Temporal order in which divergences occurred are shown
Can show amount of change which has occurred since a divergence
What is a clade?
A monophyletic group relative to other groups i.e. an ancestor and all of its descendents
What is an outgroup?
A related group used to root the tree by providing a broader phylogenetic context
What is homoplasy/parallelism?
A similarity that is attributable the same change occurring in organisms that lack common ancestry
What is a monophyletic group?
An evolutionary assemblage or group of sequences that includes a common ancestor and all of its descendents
What is a paraphyletic group?
An artificial assemblage that includes a common ancestor and some but not all of its descendents
What is a prophyletic group?
An artificial assemblage derived from two or more distant ancestors
What is homology?
Similarity in characteristics
What is analogy?
When structures which are similar between two species that are not closely related and instead attributable to convergent evolution
What is orthologous homology?
Homologous genes that diverge through speciation
What is paralogous homology?
Genes that diverge through gene duplication events
What is xenologous homology?
genes that diverge through lateral gene transfer between genomes
How are phylogenies inferred with ancient DNA?
Allows direct tests of historic relationships among extinct species
Can infer relationships among extinct species by reconstructing relationships among extinct taxa
What are the issues with using ancient DNA as a data source?
Mitochondrial DNA is used because it is present in very high copy numbers compared to nuclear DNA
The DNA is often is exposed chemical and physical degradation due to temperature and moisture etc which impose an effective time limit
The PCR technique used to amplify the DNA gained from samples is highly susceptible to contamination
What are the evolutionary characteristics of mitochondrial DNA?
Maternal inheritance and clonal replication (no recombination)
Conserved gene order and economic structure
High mutation rate (5-10 times nuclear coding regions) useful for fine scale time determination
