envs lecture 9 pt 2

Question 1

2 classes of postzygotic barriers

Answer 1

extrinsic and intrinsic

Question 2

extrinsic postzygotic barrier

Answer 2

ecological inviability, behavioral sterility

Question 2

intrinsic postzygotic barriers

Answer 2

hybrid inviability, hybrid sterility

Question 3

What is low survival of hybrids an example of

Answer 3

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

Question 3

describe intrinsic postzygotic barrier

Answer 3

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

Question 3

example of behavioral sterility (postzygotic)

Answer 3

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

Question 4

what is hybrid variability reduced by

Answer 4

incompatible interactions among genes from the two populations

Question 5

how else can hybrid fertility be reduced

Answer 5

by differences in number or structures of chromosomes

Question 6

example of intrinsic post-zygotic barrier

Answer 6

Dobzhansky-Muller incompatibility

Question 7

what is Dobzhansky-Muller incompatibility

Answer 7

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

Question 8

another definition of Dobzhansky-Muller incompatibility

Answer 8

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

Question 9

what is Dobzhansky-muller a model of

Answer 9

hybrid incompatibility

Question 10

what is another definition of Dobzhanksy-Muller

Answer 10

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

Question 11

another rule associated w/ intrinsic post-zygotic

Answer 11

Haldane’s Rule

Question 12

Haldane’s rule

Answer 12

hybrid inviability or sterility often limited to heterogametic sex

Question 13

explain Haldane’s rule

Answer 13

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

Question 14

describe Haldane’s rule in males

Answer 14

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

Question 15

describe Haldane’s rule in females

Answer 15

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

Question 16

who is heterogametic in mammals

Answer 16

males

Question 17

so who is sterile in mammals

Answer 17

male hybrids

Question 18

who is heterogametic in birds and butterflies

Answer 18

females

Question 19

so who is sterile in birds and butterflies

Answer 19

females

Question 20

what is cytonuclear incompatibility

Answer 20

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

Question 21

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

Answer 21

genetic mismatch b/w mitochondrial and nuclear genes

Question 22

why do paternal backcross (cytonuclear incompatibility) have low fitness

Answer 22

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

Question 23

describe offspring of maternal backcross (cytonuclear incompatibility)

Answer 23

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

Question 24

what is cytonuclear incompatibility

Answer 24

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

Question 25

what do common shrew in siberia have

Answer 25

two chromosomal races that form a narrow hybrid zone

Question 26

what do chromosomal races in common shrew form

Answer 26

narrow hybrid zone

Question 27

what do chromosomal races differ by

Answer 27

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

Question 28

what happens in meiosis of hybrids

Answer 28

multiple rearrangements cause a chain of 9 chromosomes to form

Question 29

what does this chain of 9 chromosomes do

Answer 29

irregular segregation causes unbalanced gametes and low fertility

Question 30

what does a transect in common shrew show

Answer 30

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

Question 31

what happens to chromosome configuration of either race

Answer 31

cannot increase within populations of the other race,

Question 32

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

Answer 32

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

Question 33

what kind of isolation evolves faster in flies and fishes

Answer 33

prezygotic isolation evolves faster than post-zygotic

Question 34

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

Answer 34

amount of time since their lineages split

Question 35

what is time estimated by

Answer 35

genetic distance b/w each pair

Question 36

how is strength of pre-zygotic isolation measured

Answer 36

by observing mating between flies in the lab

Question 37

how is strength of post-zygotic isolation measured

Answer 37

by survival and fertility of hybrid individuals

Question 38

when does strong pre-zygotic isolation evolve

Answer 38

shortly after isolation (at small genetic distances)

Question 39

when does strong post-zygotic isolation evolve

Answer 39

only after strong pre-zygotic isolation

Question 40

at what distance does pre-zygotic isolation appear

Answer 40

relatively small genetic distances

Question 41

what does value of 0 indicate

Answer 41

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

Question 42

what does value of 1 indicate

Answer 42

complete reproductive isolation

Question 43

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

Answer 43

sympatric species

Question 44

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

Answer 44

sympatric species

Question 45

what is genetic distance (an index of)

Answer 45

time since divergence

Question 46

what is seen at small genetic distances

Answer 46

sympatric pairs show strong isolation

Question 47

do sympatric pairs show strong isolation at small genetic distances

Answer 47

yes

Question 48

do allopatric pairs show strong isolation at small genetic distances

Answer 48

no

Question 49

how long do sympatric sister species of Drosophila take to evolve

Answer 49

200,000 years

Question 50

how long do allopatric species of Drosophila take to evolve

Answer 50

1.1-2.7 million years

Question 51

do prezygotic barriers always evolve to completion

Answer 51

no; may not evolve to completion

Question 52

can pre-zygotic barriers become weaker

Answer 52

yes

Question 53

how can pre-zygotic barriers become weaker

Answer 53

if habitats change

Question 54

what does increasing turbidity in lake victoria cause

Answer 54

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

Question 55

what is differences in male coloration in fish the basis of

Answer 55

sexual isolation

Question 56

what happens to fish species that were previously isolated in lake

Answer 56

now hybridizing

Question 57

is strong postzygotic isolation irreversible

Answer 57

probably

Question 58

what is strong post-zygotic isolation

Answer 58

complete hybrid sterility

Question 59

what are prezygotic barriers for these fish

Answer 59

attraction of females to brightly colored males

Question 60

how does this rapid response reverse

Answer 60

since these are pre-zygotic barriers

Question 61

what does speciation proceed quickly with

Answer 61

with pre-zygotic barriers

Question 62

what takes much longer

Answer 62

formation of post-zygotic barriers

Question 63

what is another way speciation can occur

Answer 63

polyploidy

Question 64

where is speciation by polyploidy common in

Answer 64

plants (15%)

Question 65

where is speciation by polyploidy rare in

Answer 65

animals

Question 66

what does speciation by polyploidy change

Answer 66

changes amount of gene products, phenotypes, environmental tolerances

Question 67

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

Answer 67

tetraploids

Question 68

describe the tetraploid offspring compared to parents

Answer 68

reproductively isolated

Question 69

allotetraploids

Answer 69

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

Question 70

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

Answer 70

ecological differences that could reduce the opportunity for crossing between them

Question 71

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

Answer 71

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

Question 72

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

Answer 72

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

Question 73

does speciation occur at same or varying rates

Answer 73

varying rates; sometimes instantaneous, sometimes over millions of years

Question 74

what mechanisms are involved in speciation

Answer 74

various reproductive isolating mechanisms

Question 75

can multiple reproductive isolating mechanisms involved in speciation operate simultaneously

Answer 75

yup

Question 76

describe isolating mechanisms as the basis of speciation

Answer 76

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

Question 77

which kind of isolating mechanism evolves faster

Answer 77

pre-zygotic isolating mechanisms

Question 78

is hybridization between species normal or rare

Answer 78

not unusual

Question 79

what can hybridization b/w species lead to

Answer 79

formation of stable hybrid zones, introgression, merging of species

Question 80

what must populations have in order to be considered different species

Answer 80

some level of genetic differentiation