Lecture 3 Flashcards

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1
Q

systematists

A

those who engage in systematics

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2
Q

changes in systematics since 1960s

A

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

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3
Q

molecular systematics

A

using proteins, DNA, and RNA, accelerated rate of taxonomic change

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4
Q

stratigraphy

A

temporal order in which fossils occur

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5
Q

Willi Hennig

A

German entomologist, invented Hennigian systematics in the 1950s

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6
Q

purpose of Hennigian systematics

A

objective and transparent, classifications that reflect ancestor-descendant relationships

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7
Q

clade

A

a group of organisms with shared, derived characteristics

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8
Q

Hennig’s approach aka

A

cladistics or phylogenetic systematics

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9
Q

cladogram

A

branching diagram showing these hypothesized relationships

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10
Q

length of branches on cladogram

A

do not mean anything

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11
Q

node/branching point

A

where lineages diverge (on cladogram)

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12
Q

dichotomy

A

fully resolved split into two taxa

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13
Q

polytomy

A

unresolved pattern of divergence

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14
Q

phylogenetic hypothesis

A

created by systematists using information such as morphology, behaviour, DNA sequences, and biochemistry

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15
Q

ingroup

A

the group whose relationships they are interested in untangling

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16
Q

character

A

each type of structure, behaviour, etc

17
Q

state

A

manifestation of character in a particular taxon

18
Q

outgroups

A

taxa related to the ingroup, but diverged at an earlier time

19
Q

parsimony

A

goal of a cladistic analysis is to construct a set of nested relationships that minimizes the number of times a character has to change states

20
Q

principle of parsimony aka occam’s razor

A

if one must postulate a number of unknowable events, the best hypothesis is the one requiring the fewest postulates

21
Q

outgroup state

A

set at ‘0’ and considered to be ancestral (original)

22
Q

derived state

A

different from that in outgroup, coded as 1

23
Q

character-state polarization

A

direction of changes in the character is decided

24
Q

sister taxa

A

closest relative in a clade

25
Q

synapomorphy

A

shared derived state (only state useful for reconstructing phylogenetic relationships)

26
Q

symplesiomorphy

A

shared ancestral state

27
Q

autapomorphy

A

unique derived character state present in only one taxon

28
Q

homologous

A

same character state same origin

29
Q

analogous/homoplasious/convergent

A

character state appears same, evolved independently

30
Q

molecular phylogenetics

A

matching of bases in selected gene sequences

31
Q

phylogram

A

trees in which numbers of differences between taxa are represented by branch lengths

32
Q

molecular clock

A

assumption of relatively constant rate of mutation accumulation allow branch lengths that may reflect time since divergence, requires calibration through fossil data

33
Q

maximum parsimony in molecular phylogenetics

A

choose the tree that requires the fewest total number of base pair changes

34
Q

maximum likelihood in molecular phylogenetics

A

selecting the best tree involves incorporating ‘rules’ about how DNA is most likely to change (ex. silent mutations more likely)

35
Q

monophyletic

A

true clades - contain a common ancestor and all of its descendants

36
Q

polyphyletic

A

taxa that do not share recent ancestor grouped together

37
Q

paraphyletic

A

result of the removal of taxa that are highly divergent from the rest of their clade