26 Flashcards
shared ancestral character
character that originated in an ancestor of the taxon
shared derived character
an evolutionary novelty unique to a particular clade
hair is an example of this in mammals
Phylogenies are inferred from _____ and _______
morphological and molecular data
clade
a monophyletic group that includes an ancestral species and all of its descendant s
a group of taxa that includes an ancestor and all its descendants
systematics
establishing degrees of relatedness (evolutionary relationships) among both living and extinct species.
phylogeny
the evolutionary history of a taxonomic group
evolutionary history of species or groups of species
Phylogenetic tree
a graphical summary of this history
homologies
Phenotypic and genetic similarities due to shared ancestry
analogy
similarity due to convergent evolution
Cladistics
an approach to systematics where common ancestry is the primary criterion used to classify organisms
taxonomy
how organisms are named and classified
sister taxa
groups of organisms that share an immediate common ancestor that is not shared by any other group (chimps and humans)
• Sister taxa usually refer to the tips
Monophyletic
“single tribe”- signifying that it consists of an ancestral species and all of its descendants
Paraphyletic
“beside the tribe”- consists of an ancestral species and some but not all of its descendants
Polyphyletic
“many tribes”- includes distantly related species but DOES NOT include their most recent common ancestor
plesiomorph
An organism which represents a primitive state of evolution relative to another organism.
apomorph
An organism existing in an evolutionary state that represents a morphological change as compared to a previous state.
synapomorphs
a characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.
possession by two or more organisms of a characteristic inherited exclusively from their common ancestor.
maximum parsimony
simplest explanation that is consistent with the facts
used to determine the best possible evolutionary relationship among the ingroup taxa, measured by the fewest required character changes.
The scientific discipline concerned with naming an organism is called
taxonomy
The best classification system is that which most closely
reflects evolutionary history
According to Darwin, the more closely related two different organisms are, the
the more recently they shared a common ancestor
Parasitic species (organisms that feed off of other organisms without killing them) tend to have simple morphologies. Which of the following statements best explains this observation?
Simple morphologies have been naturally selected for in most parasites
In a comparison of birds and mammals, having four limbs is
a shared ancestral character.
To apply parsimony to constructing a phylogenetic tree,
choose the tree that represents the fewest evolutionary changes, in either DNA sequences or morphology.
Three living species X, Y, and Z share a common ancestor T, as do extinct species U and V. A grouping that consists of species T, X, Y, and Z (but not U or V) makes up
a paraphyletic group
If you were using cladistics to build a phylogenetic tree of cats, which of the following would be the best outgroup?
wolf
what do branch lengths represent?
genetic change.
varying branch lengths indicate that the gene has evolved at different rates in different lineages
The relative lengths of the frog and mouse branches in the phylogeny in Figure 26.13 indicate that
(pg 560)
the homolog has evolved more slowly in mice.
phylogenetic trees show _____, not similarities
historical relationships
what do branches represent?
populations through time
what does a node represent?
where lineages diverge
basal taxon
a lineage that diverges from all other members early in history
a taxon is equivalent to a clade only if it is _____
monophyletic
maximum likelihood
given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events
outgroup
a species that is closely related but not part of the group of species we are studying
