8/31 notes Flashcards
phylogeny
a diagram depicting evolutionary relationships
what does a phylogeny look like?
often looks like a tree, so it can also be called a phylogenetic tree
speciation
through time, evolutionary lineages (species) can persist, go extinct, or give rise to new lineages
tree parts
- node
- internode
- tip
- root
- outgroup
- ingroup
- polytomy
groups
- monophyly
- clade
- paraphyly
- sister taxa
trait similarity
- homology
- homoplasy
- coonvergence
- parallelism
- reversal
types of traits
- apomorphy
- synapomorphy
- plesiomorphy
- symplesiomorphy
apomorphy trait type
derived traits
synapomorphy trait type
shared & derived traits
plesiomorphy trait type
ancestral traits
symplesiomorphy trait type
shared & ancestral traits
common name for internodes
branches
taxon
a formally named group of organisms such as a species, genus, or family
nodes
branching points in a phylogenetic tree, most recent common ancestor of two or more groups
what do nodes connect?
sister taxa
what do nodes represent?
- ancestors
- where one lineage splits into two or more descendants
how to interpret a tree
look for common ancestors and the descendants of those common ancestors
clade
- all the descendants of a common ancestor
- also called monophyletic groups
all extant members of a clade are …
equally related to the most common ancestor
does rotating nodes alter relationships?
no
does pruning a tree alter realtionships?
no
can tree be drawn in different ways?
yes
four main types of phylogenetic trees?
- diagonal up
- diagonal down
- rectangular
- circle
hard polytomy
simultaneous divergence
soft polytomy
unresolved relationships
monophyletic group
all the descendants of a common ancestor
another term for monophyletic group
clade
paraphyletic group
an ancestor and some, but not all of its descendants
if there is a problem with paraphyly, why does paraphyly persist?
- tradition
- adaptive zones
polyphyletic group
a group is not monophyletic and does not include the common ancestor. This is always a mistake, and the features used to define such groups are usually convergently evolved
homology
a trait in two or more taxa that was inherited from a common ancestor
homoplasy
similarity found in different species that is due to convergent evolution, parallelism, or reversal
(not a common ancestor)
short hand definition of homoplasy
false homology, or analogy
the three causes of homoplasy
- convergent evolution
- parallelism
- reversal
convergent evolution
similarity between species that is caused by a similar, but evolutionary independent, response to a common set of selection pressures
parallel evolution
- convergent within a species or between closely related species
- differs from convergent evolution because related species can take advantage of the same developmental mechanisms or gene flow
homoplasy reversal
loss of a trait –> trait re-evolved
homoplasy reversal example
larvae –> loss of larvae –> larvae re-evolved
shared traits
present in two or more taxa
derived traits
change from the ancestral condition
synapomorphy
- shared, derived traits
- provides evidence of common descent
automorphy
- a derived character found in only one taxon in a tree
- does not provide evidence for relationships
plesiomorphy
- ancestral trait
- shared ancestral characters are a means of phenotypic similarity, but do not provide evidence of common ancestor
symplesiomorphy
a means of similarity, but does not define clades
taxa defined by symplesiomorphy are often …
paraphyletic
the three kinds of similarity
- symplesiomorphies
- synapomorphies
- homoplasy
only ________ provide evidence of _________________
evidence, common ancestry
why phylogeny is hard to reconstruct
there are many ways to look similar, but only some kinds of similarity provide evidence for common ancestry
