Oct 18 Flashcards Preview

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Flashcards in Oct 18 Deck (41):
1

The sphynx (hairless) and tabby (haired) cats are more closely related than the tabby cat and bobcat. Therefore, the hair trait is

Symplesiomorphic

2

Which DNA substitution model weights transversions and transitions differently?

Kimura Two-­Parameter

3

Bootstrapping provides confidence about
a) how the data supports the inferred tree
b) accuracy of the evolutionary history

a) how the data supports the inferred tree

4

What do species trees do?

recover the historical patterns of descent for populations, species, genera, etc.

5

What do gene trees do?

reflect the evolutionary history of a single locus

6

TRUE/FALSE
Gene trees and species trees are always congruent

FALSE

7

Essential genes evolve/acquire mutations (slowly/quickly)

slowly

8

What does the 16S rRNA gene do?

essential for the catalytic functions of the ribosome

9

TRUE/FALSE
Evolutionary trajectory of essential or highly conserved genes often parallels that of their host species

TRUE

10

What are 3 examples of horizontal gene transfer?

-viral transfer
-conjugation in bacteria (antibiotic resistance)
-hybridization between closely related species

11

What phenomenon makes it difficult to construct phylogenies?

horizontal gene transfer

12

What is the evolutionary species concept?

Species are populations with a shared evolutionary history and fate

13

What is the phenetic species concept?

delimits species based on shared traits

14

What is a challenge in the phenetic species concept?

Which traits to look at?

15

What is the biological species concept?

delimits species based on populations capable of interbreeding

16

What defines evolutionary fate in the biological species concept?

gene flow

17

What is the phylogenetic species concept?

delimits species by resolving the smallest monophyletic clade with members uniquely sharing the derived traits

18

Does the phylogenetic species concept have inherent taxonomic hierarchy?

YES

19

What do distinct evolutionary histories imply in the phylogenetic species concept?

lack of gene flow

20

In the phylogenetic species concept species delimitations may change if...

unanticipated gene flow occurs

21

What is allopatric speciation?

Reproductive incompatibility occurs in physically separated populations-->genetic drift, accumulation of mutations and natural selection cause populations to diverge as different alleles are fixed within them

22

The dumbbell model describes...

allopatric speciation
geographic isolation-->reproductive isolation

23

The peripheral isolate model describes...

allopatric speciation
dispersal to isolated region

24

What is parapatric speciation?

1) gradient or cline causes adjacent populations to experience different selective conditions
2) but the populations can still mate, generating hybrids
3) Hybrids may lack traits that facilitate success in any part of the cline, causing them to be outcompeted by nonhybrids

25

What does bounded hybrid superiority suggest?

hybrids occupying the hybrid zone harbor unique traits exclusive of the progenitors that make them well-suited to environmental conditions not found in either extreme of the cline

26

What is sympatric speciation?

speciation in the absence of abiotic/biotic barriers

27

Two genetically related cichlids arose in a small, young lake with no obvious barriers between these species to prevent gene flow. Diet appeared to drive the divergence as each species was well-adapted to their habitats and preferred within-species mating, driving fixation of divergent alleles. This is an example of what type of speciation?

sympatric speciation

28

Reduced gene flow between apple maggots that feed on different host trees is an example of what type of speciation?

sympatric

29

What are 3 parts of sympatric speciation?

1) no physical or spatial barriers
2) requires an instantaneous mechanism
3) niche partitioning (subsets specialize on particular resource) and adaptive radiation

30

What is character displacement?

Selection acts to exaggerate differences between sympatric species and thus reduces direct competition

31

Why don't species merge? What is the underlying assumption?

Reproductive character displacement will favor conspecific mating over hybrid mating; assumes reduced hybrid fitness

32

Behavioral, temporal, and habitat are what type of reproductive isolation?

Prezygotic isolating mechanisms

33

Zygote in viability, sterile hybrids, and sterile backcrosses are what type of reproductive isolation?

Postzygotic isolating mechanisms

34

What is the difference btw prezygotic and postzygotic isolating mechanisms?

Prezygotic isolating mechanisms prevent mating or successful fertilization between different species

Postzygotic isolating mechanisms affect zygote/embryo survival

35

What is ploidy?

Change in chromosome number

36

What are problems of ploidy?

-meiosis can go awry
-hybrids may survive but they are sterile

37

What is a problem of chromosomal rearrangement?

dysfunctional gametes (extra or no copies of important genes are passed on)-->unfit hybrid

38

What are 2 causes of reproductive isolation?

ploidy
chromosomal rearrangement

39

What is Dobzhansky-Muller incompatibility?

negative epistasis btw alleles in heterozygotes (hybrids)

40

What is heterogametic sex?

sex chromosomes are not the same ie. males

41

What is Haldane’s dominance rule?

If hybrids have reduced fitness, then hybrids will be under strong negative selection in heterogametic sexes ie. in XX deleterious traits are masked by in XY they are not