trees Flashcards
chiridium
muscular jointed limb with well-defined digits
polytomy
uncertainty regarding evolutionary relationships of descendant taxa
more than two species off a single node
dichotomy
two species per node
incertae sedis
uncommon placement
temporal fenestrae
shift in jaw muscle attachment
anapsid
diapsid
synapsid
trees show relationships
related taxa share more characters in common
skeletal morphology, embryonic development, DNA sequences
FOCUSES ON COMMON ANCESTRY
similar traits, but not due to ancestry?
- -convergent evolution
- -reversal
- -homoplasy
convergent evolution
similar traits evolved independently in different lineages
reversal
derived trait lost and ancestral trait re-established
homoplasy
similarity unrelated to common descent
“noise” in the data set
homology
features/traits with similar origin (embryonic/alleles); derived from common ancestor
homologous traits may/may not have similar function
Law of Parsimony
goal is to minimize homoplasy; minimize number of evolutionary steps to explain the data
The simplest explanation that accounts for the preponderance of the data we have is more likely to be correct
outgroup
ancestral
related, but less closely than groups of interest, diverged early
monophyletic
“one tribe”
an ancestor plus all its descendants
paraphyletic
an ancestor plus some but not all descendants
polyphyletic
the descendants of two or more ancestors
apomorphic trait
change from the ancestral condition
apomorphy
derived - descendant condition
plesiomorphy
primitive - ancestral condition
symplesiomorphy
shared ancestral trait, ancestral trait shared by 2+ taxa
synapomorphy
shared derived trait, 2+ taxa have a derived trait inherited from a common ancestor
Is a trait synapomorphic or symplesiomorphic?
Ask two questions…
- Is the feature present in all members of a group?
- Is feature found in other group?
If yes to both, trait is plesiomorphic
If yes to 1, no to 2, trait is apomorphic
