Lecture 3 Flashcards
systematists
those who engage in systematics
changes in systematics since 1960s
focus has switched from adding new taxa to methods for determining relatedness among taxa, desire for evolutionarily informative classifications means that old taxonomies must be changed
molecular systematics
using proteins, DNA, and RNA, accelerated rate of taxonomic change
stratigraphy
temporal order in which fossils occur
Willi Hennig
German entomologist, invented Hennigian systematics in the 1950s
purpose of Hennigian systematics
objective and transparent, classifications that reflect ancestor-descendant relationships
clade
a group of organisms with shared, derived characteristics
Hennig’s approach aka
cladistics or phylogenetic systematics
cladogram
branching diagram showing these hypothesized relationships
length of branches on cladogram
do not mean anything
node/branching point
where lineages diverge (on cladogram)
dichotomy
fully resolved split into two taxa
polytomy
unresolved pattern of divergence
phylogenetic hypothesis
created by systematists using information such as morphology, behaviour, DNA sequences, and biochemistry
ingroup
the group whose relationships they are interested in untangling