Exam 3

Question 1

Phylogenetic trees

Answer 1

Illustrate hypothesized evolutionary relationships
Best inference based on available data
Subject to change

Question 2

Node

Answer 2

Point of divergence on phylogenetic tree

Speciation event

Question 3

Extant species

Answer 3

Living species

Question 4

What determines the relatedness of 2 species?

Answer 4

How recently they shared a common ancestor
NOT number of nodes separating them
NOT how close they are on the tree

Question 5

Character state reconstruction

Answer 5

Inferring evolutionary history of traits based on their distribution in extant species
Follows principle of maximum parsimony

Question 6

Maximum parsimony

Answer 6

Maximum likeliness
Simpler explanations are favored
Simpler= fewer evolutionary transitions

Question 7

Evolutionary transition

Answer 7

Gain or loss of a trait

Question 8

Constructing trees

Answer 8

Follows principle that close relatives share more traits than distant relatives
Assumes maximum parsimony
Choose set of traits to compare among species
Construct all possible trees
Count how many trait transitions must occur for each tree
The most likely tree has the fewest transitions

Question 9

Choosing traits for character state reconcstruction

Answer 9

More is better
May be morphologic or genetic
Beware of “noise” in data set

Question 10

Noise

Answer 10

Information that can lead you astray

Question 11

2 sources of noise

Answer 11

Convergent evolution

Reversals

Question 12

Convergent evolution

Answer 12

Leads to analogous traits

Question 13

2 reasons traits may be similar

Answer 13

Homology or analogy

Question 14

Homologous traits

Answer 14

Traits that are similar between species because they were inherited from a common ancestor
Often useful when constructing trees

Question 15

Analogous traits

Answer 15

Traits that are similar between species because of same selection pressure, NOT inheritance from common ancestor
Lead to convergent evolution
Not helpful for trees
Look at gene expression and try knocking out genes to see if traits are analogous

Question 16

Reversals

Answer 16

Derived traits revert to ancestral form

Ex: Body fur that we lost over time

Question 17

Evidence of Evolution MUST demonstrate

Answer 17

Change over time

Common ancestry

Question 18

7 Evidences of evolution

Answer 18

1. Artificial Selection
2. Fossils
3. Vestigial structures
4. Homology
5. Genetic analysis
6. Biogeography
7. Natural Selection in Action
   * All support each other as well

Question 19

Artificial selection

Answer 19

Demonstrates that organisms can change; they’re not fixed in form

Question 20

Genetic analysis

Answer 20

1. The more closely related 2 species are according to the fossil record, the more similar their DNA’s, as would be predicted by common ancestry
2. The universality of the genetic code
3. Phylogenetic patterns in ERVs

Question 21

Endemic species def.

Answer 21

Species found nowhere else

Question 22

Natural selection in action

Answer 22

Evolution we can see happening quickly

Ex: evolution of body size in finches; evolution of drug resistance in bacteria/viruses

Question 23

Sickle-cell alleles take home messages

Answer 23

Selection and drift act on allele frequencies simultaneously
Selection is subject to trade-offs, which vary across environments
Evolution is quantitative