Lecture 2: Cladistics

Question 1

monophyletic

Answer 1

descended from common ancestor and includes all descendants

Question 2

paraphyletic

Answer 2

descended from common ancestor but does not include all descendants

Question 3

polyphyletic

Answer 3

descended from a common ancestral species but does not share their most recent common ancestor

unrelated organisms from more than one ancestor

Question 4

autapomorphy

Answer 4

trait unique to lineage

Question 5

synapomorphy

Answer 5

derived character shared by clade members

used to resolve phylogenetic relationships

Question 6

symplesiomorphy

Answer 6

ancestral character state shared by two or more lineages in a particular clade

does not necessarily disitnguish the groups from other clades though

Question 7

ancestral character

Answer 7

similarity that is inherited from the most recent common ancestor of the ENTIRE group

Question 8

derived character

Answer 8

similarity that arose more recently and is shared only by a subset of the species

only shared derived characters are considered informative about evolutionary relationships

Question 9

Clade

Answer 9

species that share a common ancestor as indicated by the posession of shared derived characters

Question 10

Homoplasy

Answer 10

a shared character state that has not been inherited from a common ancestor (aka analogous trait)

involves convergent evolution and evolutionary reversal

Question 11

outgroup

Answer 11

• first group seen on phylogenetic tree
• outgroup has 1 trait shared by all groups, but no other traits