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Flashcards in Exam 3 Deck (23)
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1

Phylogenetic trees

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

2

Node

Point of divergence on phylogenetic tree
Speciation event

3

Extant species

Living species

4

What determines the relatedness of 2 species?

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

5

Character state reconstruction

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

6

Maximum parsimony

Maximum likeliness
Simpler explanations are favored
Simpler= fewer evolutionary transitions

7

Evolutionary transition

Gain or loss of a trait

8

Constructing trees

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

9

Choosing traits for character state reconcstruction

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

10

Noise

Information that can lead you astray

11

2 sources of noise

Convergent evolution
Reversals

12

Convergent evolution

Leads to analogous traits

13

2 reasons traits may be similar

Homology or analogy

14

Homologous traits

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

15

Analogous traits

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

16

Reversals

Derived traits revert to ancestral form
Ex: Body fur that we lost over time

17

Evidence of Evolution MUST demonstrate

Change over time
Common ancestry

18

7 Evidences of evolution

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

19

Artificial selection

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

20

Genetic analysis

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

21

Endemic species def.

Species found nowhere else

22

Natural selection in action

Evolution we can see happening quickly
Ex: evolution of body size in finches; evolution of drug resistance in bacteria/viruses

23

Sickle-cell alleles take home messages

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