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evolution > envs lecture 9 pt 2 > Flashcards

envs lecture 9 pt 2 Flashcards

1
Q

2 classes of postzygotic barriers

A

extrinsic and intrinsic

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2
Q

extrinsic postzygotic barrier

A

ecological inviability, behavioral sterility

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2
Q

intrinsic postzygotic barriers

A

hybrid inviability, hybrid sterility

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3
Q

What is low survival of hybrids an example of

A

postzygotic isolation caused by an extrinsic factor (postzygotic ecological inviability)

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3
Q

describe intrinsic postzygotic barrier

A

hybrids have high mortality or are partly/entirely sterile, regardless of environment

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3
Q

example of behavioral sterility (postzygotic)

A

songs of hybrid grasshoppers are intermediates, don’t attract mates

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4
Q

what is hybrid variability reduced by

A

incompatible interactions among genes from the two populations

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5
Q

how else can hybrid fertility be reduced

A

by differences in number or structures of chromosomes

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6
Q

example of intrinsic post-zygotic barrier

A

Dobzhansky-Muller incompatibility

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7
Q

what is Dobzhansky-Muller incompatibility

A

alleles A1 and B2 and A2 and B2 have never been in the same population, so no selection for them to function well together; may be incompatible

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8
Q

another definition of Dobzhansky-Muller incompatibility

A

when population is split into 2, A evolves into a in one population, B evolves into b in another population; mutually incompatible

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9
Q

what is Dobzhansky-muller a model of

A

hybrid incompatibility

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10
Q

what is another definition of Dobzhanksy-Muller

A

new alleles at diff loci not in same population; haven’t been selected to function well together

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11
Q

another rule associated w/ intrinsic post-zygotic

A

Haldane’s Rule

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12
Q

Haldane’s rule

A

hybrid inviability or sterility often limited to heterogametic sex

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13
Q

explain Haldane’s rule

A

in mammals, males (XY) are heterogametic, male hybrids are often sterile, in birds (ZW) and butterflies females are heterogametic; females often sterile

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14
Q

describe Haldane’s rule in males

A

in mammals, males (XY) are heterogametic, and male hybrids are sterile

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15
Q

describe Haldane’s rule in females

A

in birds and butterflies females (ZW) are heterogametic, females are sterile

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16
Q

who is heterogametic in mammals

A

males

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17
Q

so who is sterile in mammals

A

male hybrids

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18
Q

who is heterogametic in birds and butterflies

A

females

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19
Q

so who is sterile in birds and butterflies

A

females

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20
Q

what is cytonuclear incompatibility

A

low fitness of hybrids b/w populations w/ most mismatch of nuclear and mitochondrial genes

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21
Q

what is low fitness of hybrids b/w populations caused by (in cytonuclear incompatibility)

A

genetic mismatch b/w mitochondrial and nuclear genes

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22
Q

why do paternal backcross (cytonuclear incompatibility) have low fitness

A

most of nuclear genes come from population B, are mismatched to mitochondrial genes from population A

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23
Q

describe offspring of maternal backcross (cytonuclear incompatibility)

A

most nuclear genes come from same population as mitochondria –> normal, high survival

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24
Q

what is cytonuclear incompatibility

A

low fitness of hybrids b/w populations w/ most mismatch of nuclear and mitochondrial genes

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25
Q

what do common shrew in siberia have

A

two chromosomal races that form a narrow hybrid zone

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26
Q

what do chromosomal races in common shrew form

A

narrow hybrid zone

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27
Q

what do chromosomal races differ by

A

fusion of single-armed chromosomes (o and g) into double armed chromosomes

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28
Q

what happens in meiosis of hybrids

A

multiple rearrangements cause a chain of 9 chromosomes to form

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29
Q

what does this chain of 9 chromosomes do

A

irregular segregation causes unbalanced gametes and low fertility

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30
Q

what does a transect in common shrew show

A

cline in frequency of Novosibirsk chromosome arrangement less than 9 km wide

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31
Q

what happens to chromosome configuration of either race

A

cannot increase within populations of the other race,

32
Q

why can’t chromosome configuration of either race not increase within populations of the other race

A

b/c meiosis in F1 hybrids produces gametes that lack some chromosomal regions

33
Q

what kind of isolation evolves faster in flies and fishes

A

prezygotic isolation evolves faster than post-zygotic

34
Q

what does the strength of prezygotic and post-zygotic reproductive isolation b/w pairs of populations and species of Drosophila increase w/

A

amount of time since their lineages split

35
Q

what is time estimated by

A

genetic distance b/w each pair

36
Q

how is strength of pre-zygotic isolation measured

A

by observing mating between flies in the lab

37
Q

how is strength of post-zygotic isolation measured

A

by survival and fertility of hybrid individuals

38
Q

when does strong pre-zygotic isolation evolve

A

shortly after isolation (at small genetic distances)

39
Q

when does strong post-zygotic isolation evolve

A

only after strong pre-zygotic isolation

40
Q

at what distance does pre-zygotic isolation appear

A

relatively small genetic distances

41
Q

what does value of 0 indicate

A

pairs are no more isolated than conspecific individuals (same species)

42
Q

what does value of 1 indicate

A

complete reproductive isolation

43
Q

what does strength of prezygotic isolation increase more rapidly b/w

A

sympatric species

44
Q

does strength of pre-zygotic isolation increase more rapidly b/w allopatric or sympatric species

A

sympatric species

45
Q

what is genetic distance (an index of)

A

time since divergence

46
Q

what is seen at small genetic distances

A

sympatric pairs show strong isolation

47
Q

do sympatric pairs show strong isolation at small genetic distances

A

yes

48
Q

do allopatric pairs show strong isolation at small genetic distances

A

no

49
Q

how long do sympatric sister species of Drosophila take to evolve

A

200,000 years

50
Q

how long do allopatric species of Drosophila take to evolve

A

1.1-2.7 million years

51
Q

do prezygotic barriers always evolve to completion

A

no; may not evolve to completion

52
Q

can pre-zygotic barriers become weaker

A

yes

53
Q

how can pre-zygotic barriers become weaker

A

if habitats change

54
Q

what does increasing turbidity in lake victoria cause

A

harder for females to see differences in male coloration that is basis for sexual isolation

55
Q

what is differences in male coloration in fish the basis of

A

sexual isolation

56
Q

what happens to fish species that were previously isolated in lake

A

now hybridizing

57
Q

is strong postzygotic isolation irreversible

A

probably

58
Q

what is strong post-zygotic isolation

A

complete hybrid sterility

59
Q

what are prezygotic barriers for these fish

A

attraction of females to brightly colored males

60
Q

how does this rapid response reverse

A

since these are pre-zygotic barriers

61
Q

what does speciation proceed quickly with

A

with pre-zygotic barriers

62
Q

what takes much longer

A

formation of post-zygotic barriers

63
Q

what is another way speciation can occur

A

polyploidy

64
Q

where is speciation by polyploidy common in

A

plants (15%)

65
Q

where is speciation by polyploidy rare in

A

animals

66
Q

what does speciation by polyploidy change

A

changes amount of gene products, phenotypes, environmental tolerances

67
Q

what does hybridization between diploids produce (in goatsbeards/tragopogon)

A

tetraploids

68
Q

describe the tetraploid offspring compared to parents

A

reproductively isolated

69
Q

allotetraploids

A

tetraploids formed by hybridization; a type of polyploidy in which an organism or cell possesses four sets of chromosomes derived from two species

70
Q

what can differences between a newly formed polyploid and its ancestor in Yarrow confer

A

ecological differences that could reduce the opportunity for crossing between them

71
Q

describe flowering time of a newly originated hexaploid (neo-6n yarrow) planted in a dry dune

A

intermediate b/w those of its tetraploid parent (4n) and existing hexaploid (6n) species

72
Q

if you think you have one species in a sample but you have two, what might you see in a hardy weinberg test?

A

no heterozygotes were observed, so no hybridization was occurring, evidence of reproductive isolation. morphological differences.

73
Q

does speciation occur at same or varying rates

A

varying rates; sometimes instantaneous, sometimes over millions of years

74
Q

what mechanisms are involved in speciation

A

various reproductive isolating mechanisms

75
Q

can multiple reproductive isolating mechanisms involved in speciation operate simultaneously

A

yup

76
Q

describe isolating mechanisms as the basis of speciation

A

some isolating mechanisms may be the basis of speciation, others may have evolved later

77
Q

which kind of isolating mechanism evolves faster

A

pre-zygotic isolating mechanisms

78
Q

is hybridization between species normal or rare

A

not unusual

79
Q

what can hybridization b/w species lead to

A

formation of stable hybrid zones, introgression, merging of species

80
Q

what must populations have in order to be considered different species

A

some level of genetic differentiation

evolution (15 decks)

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