Lecture 7 - Phylogeny Flashcards
levels of hypothesis
cladogram
pattern of branching relatedness, time-free
levels of hypothesis
phylogenetic tree
cladogram with added time dimension
levels of hypothesis
clade
all taxa (no more, no less) that are descended from a common ancestor
levels of hypothesis
grade
a group of taxa that shares a suite of functionally adaptive features
levels of hypothesis
how to get it wrong
- fooled by homoplasy (convergence)
- fooled by widespread primitive trait (homologous)
levels of hypothesis
homoplasy
independent acquisition of the same characteristics; shared morphology not inherited from a recent common ancester
levels of hypothesis
homologous traits
traits derived from the same origins
ex: humans, horse, cat, bird, whale have similar joint strucures BUT that’s because a common ancestor of all had them
homoplasy sources
convergent evolution
evolution of similar traits in distantly-related taxa through distinct developmental pathways
similarities in function, not origin
more specific than homoplasy
homoplasy sources
parallel evolution
evolution of simialr traits in closely-related taxa through the same or similar developmental pathways
homoplasy sources
reversal
change to a previously held character state
primitive & derived traits
plesiomorphies
primitive characteristics
primitive & derived traits
apomorphies
derived traits
primitive & derived traits
syn(apomorphy)
derived traits shared between taxa
primitive & derived traits
aut(apomorphy)
derived trait found in single taxon
primitive & derived traits
sym(pleisomorphy)
shared primitive traits shared between taxa
terms
crown group
living representatives of a taxon + their ancestors back to their most recent common ancestor & its descendants
terms
stem group
all fossil taxa that are more closely related to the living members of the group than to the living members of other group
ex: groups before modern humans
terms
outgroup
taxa that are closely related but do not belong to the clade being investigated
ex: Pan for analysis of hominins
modes of speciation
cladogenesis
speciation event that splits and gives rise to a new species (2 daughter species)
modes of speciation
anagenesis
change over time so drastic that it requires a new species name (daughter chronospecies), but no actual splitting event
