Tree Definitions

Question 1

rooted tree

Answer 1

a tree that has a root

Question 2

terminal branch

Answer 2

the branch of a tree containing the outgroup

Question 3

internal branch

Answer 3

the branch of a tree containing all the branches that are not the outgroup

Question 4

Unrooted tree

Answer 4

a tree that just shows the relationships between clades, but doesn’t have a root

Question 5

Monophyletic group

Answer 5

a group that contains all the descendents of a common ancestor. Also known as clades

Question 6

Polyphyletic group

Answer 6

a group of species that doesn’t include all species descended from a common ancestor

Question 7

Sister Groups

Answer 7

Pairs of monophyletic groups that together form a larger monophyletic group

Question 8

Outgroup

Answer 8

A clade that is not part of a specific clade, can only exist on rooted trees

Question 9

Can outgroups exist on rooted trees?

Answer 9

Yes, only on rooted trees

Question 10

Polytomy

Answer 10

a node that isn’t fully resolved

Question 11

lineage

Answer 11

a vague term for a path on a tree, often meaning the idea of a branch leading to a defined monophyletic group

Question 12

Characters

Answer 12

Things we measure on the things that we want to infer trees for

Question 13

Discrete characters

Answer 13

Come in one of several possibilities of a trait, e.g. presence/absence of a curl

Question 14

Continuous characters

Answer 14

characters that are measured, e.g. length of a curl, amount of red

Question 15

Distance measures

Answer 15

relations between taxa. genetic distance is the most common distance measure

Question 16

Syn apo morphies

Answer 16

shared derived character. e.g. for mammals are fur and lactation, for angiosperms are closed seeds and flowers. Are depicted as bars on trees, to imply that that trait evolved in the lineage leading to the monophyletic group.

Question 17

homologous

Answer 17

different states of the same underlying character, e.g. scales in lizards and snakes and fur in mammals

Question 18

Derived state

Answer 18

is the state of a homologous trait shared by a monophyletic group

Question 19

Apomorphy

Answer 19

derived character state (the new state)

Question 20

Plesiomorphy

Answer 20

The ancestral character state

Question 21

Symplesiomorphies

Answer 21

shared ancestral characters

Question 22

autapomorphy

Answer 22

derived character not shared among taxa on a tree

Question 23

Homeothermy

Answer 23

when a trait evolves more than once

Question 24

anapsid

Answer 24

when a trait evolves but is then lost

Question 25

Homeoplasies

Answer 25

character states which we think evolved more han once within the group we are considering

Question 26

Cladistics

Answer 26

the endeavor to identify monophyletic groups on the basis of synapomorphies

Question 27

Parallel evolution

Answer 27

when two groups evolve the same character

Question 28

consensus tree

Answer 28

different types of data may suggest different trees, so you can try to find a consensus of these different trees by looking at what they have in common. It tries to summarize the information from several different trees

Question 29

Strict

Answer 29

A type of consensus tree

Question 30

Majority-rule

Answer 30

A type of consensus tree