Lecture #3: Phylogeny Concepts II

Question 1

LO #1: Show how uncertainty is reflected on phylogenies

Answer 1

Uncertainty is reflected on phylogenies w/ the usage of polytomies

Question 2

LO #2: Interpret differences between 1. cladograms, 2. phylograms, and 3. chronograms

Answer 2

1. cladogram: order of relationships/branching
2. phylograms: branches have meaning for proportional amount of character change
3. chronograms: branch length for time

Question 3

LO #3: Trace character changes on phylogenies

Answer 3

1. identify the character you are tracing
2. look at the character states
3. map these characters on a tree to visualize

Question 4

LO #4: Define synapomorphy

Answer 4

a characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.

Question 5

LO #5: explain the difference b/w homology and homoplasy

Answer 5

homology: similarity due to common ancestry
homoplasy: similarity due to convergent evolution

Question 6

used when there is uncertainty in the branching of a phylogeny

Answer 6

polytomy

Question 7

not enough data/taxa; or data that we have leads to conflicts

Answer 7

soft polytomy

Question 8

happens when speciation happens too fast that there is no data that can resolve relationships

Answer 8

hard polytomy

Question 9

only show the order of branching; branch lengths have no meanings (tips of trees stop at the same line)

Answer 9

cladogram

Question 10

branch lengths are proportional to the amount of character change (branch lengths are not the same; there is a scale bar)

Answer 10

phylogram

Question 11

branch lengths are proportional to absolute time (timing in MYA)

Answer 11

chronogram

Question 12

a heritable feature of an organism (aka a character trait)

Answer 12

character

Question 13

the form that a character takes

Answer 13

character state

Question 14

characters onto a tree helps us visualize changes

Answer 14

tracing (mapping)

Question 15

a characteristic present in an ancestral species and shared exclusively (in more/less modified form) by its evolutionary descendants

Answer 15

synapomorphy

Question 16

a character w/ the same state as the ancestor of the group

Answer 16

ancestral trait

Question 17

a character w/ a different state as the ancestor of the group

Answer 17

derived state

Question 18

similarity due to convergent evolution

Answer 18

homoplasy

Question 19

similarity due to common ancestry

Answer 19

homology

Question 20

ex of ancestral trait and synapomorphy

Answer 20

• hair is a synapomorphy of mammals. uniquely shared only w/ mammals
• w/in mammals, hair is an ancestral trait as all mammals have hair.

Question 21

example of homoplasy vs homology

Answer 21

homoplasy: wings have evolved at least 4 times independently (convergent evolution)
homology: the bones for these creatures that fly is homologous