PPt Phylogenetics (Ex 3)

Question 1

Phylogeny

Answer 1

1. A and B are most closely related because they share a common ancestor (call the ancestor E) that C and D do not share
2. A+B+C are more closely related to each other than to D because they share a common ancestor (“F”) that D does not share

Question 2

Plesiomorphy

Answer 2

Character state found in ancestor of group

Question 3

Apomorphy

Answer 3

Derived character state in descendants of group

Question 4

Symplesiomorphy

Answer 4

Shared, ancestral character state

Question 5

Synapomorphy

Answer 5

Shared, derived character state (indicates homology)

Question 6

Monophyly

Answer 6

All the descendants of a common ancestor
Monophyletic groups

Question 7

Clade

Answer 7

A clade is a single common ancestor and all of its descendants. The arrow shows the common ancestor
Note that canids are still a good monophyletic clade within Mammalia

Question 8

Polyphyly

Answer 8

A group including those from multiple ancestors
Polyphyletic groups

Question 9

Grade

Answer 9

1. A grade is a group of organisms not based on a shared evolutionary history, but on a trait

Question 10

Paraphyly

Answer 10

Paraphyly occurs when an ancestral species, but not all of its descendants are grouped
Paraphyletic groups

Question 11

Paraphyletic groups

Answer 11

1. Reptilia is a paraphyletic group unless it includes Aves
2. Paraphyly occurs when we use apomorphies (unique traits) to group taxa
3. Birds’ scales are modified into feathers, and birds possess an endothermic metabolism which excludes them from Reptilia (“cold-blooded and scary”)
4. Birds are more closely related to crocodilians (“reptiles”) than to any other extant vertebrate

Question 12

Homology (arm bones)

Answer 12

shared ancestry

Question 13

Homoplasy

Answer 13

Traits that are functionally similar to each other but are the product of convergent evolution instead of relatedness
(Traits are functionally similar but not the same)

Question 14

Analogous structures

Answer 14

Have independent evolutionary origins…the same type of adaptation can evolve more than once in the presence of similar natural pressures

Question 15

Synapomorphy

Answer 15

1. Shared derived characters, homologous origins
2. How can we tell how well a clade is supported?
3. In part, by the number of synapomorphies
4. Few synapomorphies = weaker support
5. Many synapomorphies = stronger support

Question 16

Parsimony

Answer 16

1. How do we decide the “best” phylogeny?
2. Choose a topology with the fewest numbers of evolutionary steps or changes

Question 17

Consistency Index (CI)

Answer 17

1. This is a measure of how well an individual character fits (is compatible w/) on a phylogenetic tree
   1.5 the amount of homoplasy
2. CI = E (n-1)/State Changes (E is actually the e looking all of them thing)
3. State changes = steps = # ticks on tree