Chapter 4 : Phylogeny And Evolutionary History Flashcards
Who developed the taxonomic system?
Carolus Linnaeus
Phylogenetic Systematics
Classifying organisms according to their evolutionary histories.
Phylogeny
The branching relationships of populations as they give rise to multiple descendant populations over evolutionary time.
What does the study of phylogeny allow?
It allows us to reconstruct the tree of life and understand major events in evolutionary history.
Characters
Observable characteristics of organisms; anatomical features or behavioral patterns.
Traits
Specific values of a character; tall or short.
What type of characters are most commonly used today?
DNA sequences
What is the difference between a pedigree and a phylogeny?
Pedigree: ancestry of individuals.
- nodes = individuals
Phylogeny: ancestry of populations.
- nodes = populations
Who established the modern approach to classification?
Willi Hennig
Tree of life
Historical relationships that connect all living things
What are some examples of character?
Anatomical features, developmental or embryological processes, behavioral patterns, genetic sequences
What do phylogenies tell us?
The ancestry of a population
What do nodes in a phylogeny represent?
Populations
What is a phylogenetic tree a hypothesis about?
Evolutionary relationships
What is the location and order of phylogenetic tree hypothetically?
The way that evolutionary history has unfolded
Taxon
A branch tip that represents a group of related organisms
Nodes
The branch points where the tree splits
What do nodes represent?
Recent common ancestors to the species that come after splitting or branching point
Root
The common ancestors to all the species on the tree
Sister taxa
Taxa derived from the same node
Polytomy
A node with more than two branches arising from it
Monophyletic Group
A taxonomic group consisting of all descendants of the group’s most common ancestor and no other members
Clade
A group of species that share a single recent common ancestor
Polyphyletic Group
Do not represent proper evolutionary clades and no longer used in modern systematics
Paraphyletic Group
Contains the group’s most common ancestor but not all of its descendants
Rooted trees
Shows the common lineage from which all the species on the tree are derived is indicated at the base of the tree
What does direction in a rooted tree indicate?
Passage of time
Unrooted tree
Do not fully indicate the direction of time
What does a phylogram indicate?
Evolutionary relationships and the amount of sequence change along each branch by means differing horizontal branch lengths
Cladogram
Trees that do not have different branch lengths, the branch tips are aligned
Phylogram
Trees that represent evolutionary change with branch lengths
Chronograms
Trees that show branch lengths that represent actual time rather than the amount of evolutionary time
What does the study of phylogeny rely on?
Our observations of traits displayed by organisms
What is a homologous trait?
A trait that is found in two or more species because those species have a common ancestor
What is an analogous trait?
A trait that is shared by two or more species because the traits have risen independently in each species not because of a history of common descent
What are synamorphies?
Shared derived traits
What do evolutionary biologists use synamorphies for?
To infer the structure of phylogenetic trees
Soft polytomy
Result of insufficient phylogenetic information
Hard polytomy
Arises when three or more sampled genes trace their ancestry to a single gene in an ancestral organism
What is a node?
The point where a phylogenetic tree branches
What is a monophyletic group / clade?
A taxonomic group that consists of a unique common ancestor and each and every one of its descendant species
What does a clade always consist of?
A group of species that share a single common ancestor
What is a paraphyletic group?
A group that includes the common ancestor of all its members but does not contain each and every species that descended from that ancestor
What do the branch lengths represent in phylograms?
Evolutionary change
What are vestigial traits?
Those that have no current functionbut appear to have been important in the evolutionary past
Outgroup
A group with a known evolutionary relationship to the taxon we are studying
Synapomorphy
A derived trait that is shared in two populations because it was inherited from a recent common ancestor
Homoplasy
A trait that is similar in two species because of a convergent evolution rather than common ancestry
Symplesiomorphy
A derived trait that has arisen so recently that it appears in only one of two sister taxa
Convergent evolution
When two or more populations or species become more similar to one another because they are exposed to similar selective conditions and leads to analogous traits
Divergent evolution
When closely related populations or closely related species diverge from one another because natural selection operates differently on each of them
What does the presence of analogous traits reveal?
Natural selection generates structurally or functionally similar solutions to similar problems
