Tree Definitions Flashcards
rooted tree
a tree that has a root
terminal branch
the branch of a tree containing the outgroup
internal branch
the branch of a tree containing all the branches that are not the outgroup
Unrooted tree
a tree that just shows the relationships between clades, but doesn’t have a root
Monophyletic group
a group that contains all the descendents of a common ancestor. Also known as clades
Polyphyletic group
a group of species that doesn’t include all species descended from a common ancestor
Sister Groups
Pairs of monophyletic groups that together form a larger monophyletic group
Outgroup
A clade that is not part of a specific clade, can only exist on rooted trees
Can outgroups exist on rooted trees?
Yes, only on rooted trees
Polytomy
a node that isn’t fully resolved
lineage
a vague term for a path on a tree, often meaning the idea of a branch leading to a defined monophyletic group
Characters
Things we measure on the things that we want to infer trees for
Discrete characters
Come in one of several possibilities of a trait, e.g. presence/absence of a curl
Continuous characters
characters that are measured, e.g. length of a curl, amount of red
Distance measures
relations between taxa. genetic distance is the most common distance measure
Syn apo morphies
shared derived character. e.g. for mammals are fur and lactation, for angiosperms are closed seeds and flowers. Are depicted as bars on trees, to imply that that trait evolved in the lineage leading to the monophyletic group.
homologous
different states of the same underlying character, e.g. scales in lizards and snakes and fur in mammals
Derived state
is the state of a homologous trait shared by a monophyletic group
Apomorphy
derived character state (the new state)
Plesiomorphy
The ancestral character state
Symplesiomorphies
shared ancestral characters
autapomorphy
derived character not shared among taxa on a tree
Homeothermy
when a trait evolves more than once
anapsid
when a trait evolves but is then lost
Homeoplasies
character states which we think evolved more han once within the group we are considering
Cladistics
the endeavor to identify monophyletic groups on the basis of synapomorphies
Parallel evolution
when two groups evolve the same character
consensus tree
different types of data may suggest different trees, so you can try to find a consensus of these different trees by looking at what they have in common. It tries to summarize the information from several different trees
Strict
A type of consensus tree
Majority-rule
A type of consensus tree
