Chapter 4: The Tree of Life Flashcards
phylogeny
a visual representation of the evolutionary history of populations, genes, or species
tips
terminal ends of an evolutionary tree, representing species, molecules, or populations being compared
branches
lineages evolving through time between successive speciation events
node
a point in a phylogeny where a lineage splits (a speciation event)
internal node
nodes within a phylogeny representing ancestral populations or species
clade
an organism and all its descendants
monophyletic
a term used to describe a group of organisms that form a clade
characters
heritable aspects of organisms that can be compared across taxa
taxon
a group of organisms that are a taxonomic unit, such as a species or order (can be species, family, or class)
synapomorphy
shared derived character evolved in the immediate common ancestor of a clade & was inherited by all its descendants
cladistics
phylogenetic methods that construct trees by grouping taxa into nested hierarchies (clades) according to their synapomorphies
homoplasy
character state similarity not due to shared descent (unreliable way to build phylogeny b/c trait came from convergent evolution/evolutionary reversal)
convergent evolution
the independent origin of similar traits in separate evolutionary lineages; the same solution to an evolutionary problem (ex: dolphins and sharks are both streamlined)
evolutionary reversal
the reversion of a derived character state to its ancestral state (ex: snakes lost limbs which was a characteristic of vertebrate common ancestor)
exaptation
a trait that originates performing one function, and which is later co-opted for a new function
australopithecines
members of the hominin genus Australopithecus
polyphyletic
referring to a taxon which does not contain the most recent common ancestor of all members of the group; results when you focus on just one or two traits (like having all “flying things”)ex: pachyderms are a polyphyletic group b/c having thick skin evolved separately but they do all have it
paraphyletic
referring to a taxon which includes most recent common ancestor and some, but not all of its descendents; a really bad classification
rooted tree
straightforward progression with a clear indication of the direction of time
unrooted tree
bush-like tree which is #NotClearOn progression of time; branch tips more recent than interior nodes but can’t tell recency of branch vs branch
ingroup
the various species being studied or included in a phylogeny
outgroup
close relative of members of the ingroup which provides a basis of comparison
homoplasy
analogous trait in a tree; can’t figure out exact sequence (bad way to determine tree)
symplesiomorphy
new trait in a lineage that appears in one taxon (bad way to determine tree)