T4 - Systematics and Phylogeny Flashcards
Systematics
The theory and practice of classifying organisms based on phylogeny
Phylogeny
the current hypothesis for the evolutionary history of a species or group of related species
Phylogenetic trees
Show the hypotheses of the evolutionary relationships between organisms through evolutionary descent and common ancestors
What are the two ways we can infer phylogeny?
- morphological data
- molecular data
morphological data
similarities between anatomical features
molecular data
similarities in molecular structures (DNA, RNA, protein)
Speciation
the divergence of two species from a common ancestor
sister taxa
two descendants from the same node/common ancestor
Basal Taxon
species that diverges early in the evolutionary history of a group, closer to common ancestor
Clade
a piece of a phylogeny with an ancestor and al its descendants; forms a nested hierarchy
Cladograms
phylogenetic trees based oonly on evolutionary relationships
Phylograms
phylogenetic trees based on evolutionary patterns AND chronological time of evolutionary change through line lengths
Polytomies
a part of a phylogeny that speciates into 3 descendants
2 causes of phylogenetic polytomies
- Lack of knowledge
- rapid speciatione.g. maybe quick displacement of species
Name 1 similarity about groups and 1 general difference between taxonomy and systematics.
Similarity: taxonomic rank = clades
Difference: the criteria used for grouping (similarity/difference vs. phylogeny)
Homology/homologous traits
similarity in shared ancestry between two species
Analogy/Analgous traits
similarities between species due to convergent evolution
Convergent evolution
independent evolution of similar traits in different lineages
Which is used in phylogenetic trees? Homologous or analogous traits?
Homologous ONLY
Characters
anatomical, physiological, or molecular features of organisms
Ingroup vs. Outgroup
Ingroup: group of taxa whose evolutionary relationships you want to compare/determin
Outgroup: usually used as a reference point for making phylogenetic trees (basal taxon), diverged from ingroup at an earlier time
Cladistics
A method of inferring phylogeny from homologous characters
Monophyletic
a grouping that consists of only the ancestor and its descendants; clade