cycle 9 Flashcards
phylogenetic tree
a hypothesis describing the evolutionary relationships of species or any group or organisms (shows their evolutionary history)
tips/leaves
species or groups of organisms existing in the present (extant)
tip labels
names of species, letters
branches
lines to a new species
nodes
intersection of branches, represents a common ancestor
bifurcates
splits in two
monophyletic clade
all descendants of a common ancestor
outgroup
furthest from all other species, evolved from the oldest node
what does the length of the branches represent?
time, molecular distance
root
oldest, earliest node
derived traits
evolved after the most recent common ancestor of a group
ancestral traits
evolved before the most recent common ancestor of a group (traits can be lost, not all members have the trait)
parsimony
the simplest explanation is most likely (fewest evolutionary changes), used when constructing trees
shared traits
shared by at least 2 members of the group, not unique
synapomorphies
shared, derived traits (useful)
how to determine which traits are ancestral/derived?
use an outgroup (close relative known to have branched off earlier, use parsimony)
divergence
misleading dissimilarity despite close evolutionary relationship
how are organisms ideally classified?
based on monophyletic groups (many traditionally recognized groups are not monophyletic)
are unique traits useful in building a tree?
no
how do we tell if the same trait is homologous or due to convergence?
- structural/developmental similarity is more informative than superficial similarity
- build tree using other traits
- use molecular data to determine evolutionary relationships
molecular phylogenetics
using molecular differences to build evolutionary trees
