25 Phylogenetics Flashcards
Phylogeny
the evolutionary history of a group of organisms
Phylogenetic tree
a branching diagram that depicts the evolutionary relationships among species or other taxa
Tree of life
most universal phylogenetic tree that includes all organisms
Branches
a part of a phylogenetic tree that represents populations through time
Root
the most ancestral branch in a phylogenetic tree
Nodes (forks)
a point within a phylogenetic tree where two branches spit, representing the point in time when a hypothetical ancestral group (the most recent common one) split into two or more descendant groups
Tips (terminal nodes)
endpoint of a branch in a phylogenetic tree that represents a living or extinct group of genes, species, families, phyla, or other taxa
Where are taxa located in a phylogenetic tree?
On the branch tips, never within a tree, because none of the taxa (living or extinct) are presumed to be ancestors of others
Sister groups
two or more lineages that share a recent common ancestor at the node where their branches meet
Speciation event
two populations within the ancestral species become genetically isolated and diverge over a long or short time due to mutation, natural selection, and genetic drift, leading to different species
Polytomy
a node in a phylogenetic tree that depicts an ancestral branch dividing into 3 or more descendant branches, indicating insufficient data is available to know which taxa are more closely related
Character or trait
any observable characteristic (genetic, morphological, physiological, developmental, or behavioral) to be studied
Outgroup
a taxon that is closely related to the taxa being studied (a sister group) but that diverged earlier used to establish the relative timing of evolution of each character
Ancestral trait
trait found in the ancestors of a particular group
Derived trait
a trait that is a modified form of an ancestral trait, found in a descendant, and originates via mutation, selection, and genetic drift
Cladistic approach or cladistics
a method for constructing a phylogenetic tree that is based on identifying shared, derived traits called synapomorphies
Synapomorphy
a shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors i.e. a monophyletic group
Monophyletic group or clade or lineage
an evolutionary unit that includes an ancestral population and all of its descendants but no others
Principle of Parsimony
logical principle that the most likely explanation of a phenomenon is the most economical or simplest (the one with the fewest character changes)
Homology “same source” or Homologous traits
similarity among organisms of different species due to shared ancestry (e.g. all mammals have hair); used to determine monophyletic groups
Homoplasy “same form”
Similarity among organisms of different species due to reasons other than common ancestry like convergent evolution
Convergent evolution
the independent evolution of similar traits in different species due to adaptation to similar environmental conditions and a similar way of life
What is the evidence that all organisms share a common ancestor?
(1) All organisms are made of cells (2) DNA is the genetic material of all cells (3) Basic chemical building blocks are common to all cells (4) Genetic code
Cladogram
phylogeny where only the order of the nodes matter and the length of the branches is meaningless
Phylogram
phylogeny where branch length represents change; usually includes a scale bar to indicate rate of change
What are the 2 types of phylogenies?
cladogram and phylogram
