branches
lineages evolving through time that connect successive speciation or other branching events
phylogeny
a visual representation of the evolutionary history of populations, genes, or species
nodes
points in a phylogeny where a lineage splits (a speciation event or other branching event, such as the formation of subspecies)
tips
the terminal ends of an evolutionary tree, representing species, molecules, or populations being compared
internal nodes
nodes that occur within a phylogeny and represent ancestral populations or species
clades
single "branches" in the tree of life; each represents an organism and all of its descendants
monophyletic
describes a group of organisms that form a clade
polyphyletic
describes a taxon that does not include the common ancestor of all members of the taxon
paraphyletic
describes a group of organisms that share a common ancestor although the group does not include all of the descendants of that common ancestor
characters
heritable aspects of organisms that can be compared across taxa
taxa
groups of organisms that a taxonomist judges to be cohesive taxonomic units, such as a species or order
outgroups
groups of organisms (e.g., a species) that are outside of the monophyletic group being considered
-in phylogenetic studies, outgroups can be used to infer the ancestral states of characters
homoplasy
describes a character state similarity, not due to shared descent (e.g., produced by convergent evolution or evolutionary reversal)
-the similarity in appearance, not in origin
covergent evolution
the independent origin of similar traits in separate evolutionary lineages
evolutionary reversal
describes the reversion of a derived character state to a form resembling its ancestral state
parsimony
a principle that guides the selection of alternative hypotheses; the alternative requiring the fewest assumptions or steps is usually (but not always) the best
-in cladistics, scientists search for the tree topology with the least number of character-stat
homology
similar traits inherited from a common ancestor (similarity in origin)
analogy
similar adaptations favored by natural selection, in similar environments (similarity in function, not origin)
D
Which of the following is an example of homoplasy?
a. The reversion of a derived character state to its ancestral state
b. The independent origin of similar traits in separate lineages
c. The evolution of wings in both birds and bats
d. All of the above
E