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HELENP EE Evolution and Natural Selection > EE Lecture 6: Sexual Selection > Flashcards

EE Lecture 6: Sexual Selection Flashcards

1
Q

define sexual dimorphism

A

phenotypic differences between males and females of the same species

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2
Q

what is the state of having phenotypic differences between males and females of the same species

A

sexual dimorphism

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3
Q

define sexual selection

A

natural selection where some individuals outreproduce others of a pop because theyre better at securing mates

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4
Q

what does sexual selection favour

A

any heritable trait that increases reproductive success

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5
Q

what is Bateman’s principle

A 
variance in reproductive success is generally greater in males than in females
a consequence of anisogamy
females invest greater in offspring
females compete for resources
males compete for access to females
females are more choosy
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6
Q

what is Triver’s theory

A

theory of parental investment

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7
Q

what are females reproductive rates limited by

A

the number of offspring they can birth in a lifetime

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8
Q

whate are male reproductive rates limited by

A

number of females they can impregnate

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9
Q

which sex invests greater in offspring

A

females

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10
Q

which sex competes for mates as opposed to resources (mostly)

A

males

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11
Q

which sex are more choosy

A

females

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12
Q

why is there variance in reproductive success

A

females are limited by number of births in a lifetime and males arelimited by the number of females they can impregnate

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13
Q

what are male strategies for reproductive success

A 
max no. copulations 
direct contest comp for female
provide evidence of good genes to female
provide female with good resources
invest in offspring if parent certainty is high
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14
Q

under what circumstances will males invest in offspring

A

if parent certainty is high

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15
Q

what are female strategies for reproductive success

A

invest in offspring
choose males with good genes
choose males who’ll invest in offspring

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16
Q

what is Fisher’s hypothesis

A

runaway selection hypothesis

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17
Q

who thought of the runaway selection hypothesis

A

Fisher

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18
Q

what is Fisher’s runaway selection hypothesis

A

females who mate with attractive males produce attractive sons
genes for the male trait and female preference become associated
preference and the trait become magnified over time
eventually all males have the trait

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19
Q

what is Fishers runaway selection hypothesis halted by

A

natural selection

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20
Q

what is the hypothesis called where genes female preference and male traits become associated

A

Fishers runaway selection hypothesis

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21
Q

what is Zahavi’s hypothesis

A

Zahavi’s handicap hypothesis

22
Q

what is Zahavis handicap hypothesis

A

exaggerated secondary sexual traits are an honest indication of good genes
low quality males cant fake the signal because they aren’t strong enough to overcome the handicap

23
Q

what is the MHC

A 
major histocompatibility complex
3.6Mb region on short arm of chrom 6
encodes immune system proteins
repsonsible for transplant rejection
most variable part of genome
24
Q

how many bp is the MHC

where is it found

A

3.6Mb region on short arm of chrom 6

25
Q

what does MHC encode

A

immune system proteins

26
Q

what is the function of the MHC

A

recognise foreign proteins
present antigens to T cells
T cells recruit B cells
B cells produce antibodies

27
Q

how many types of molecules do MHC makes

A

class 1 and class2

28
Q

what can class 1 MHC molecules hold - why

A

class 1 MHC molecules can only hold short peptides because the binding site is closed off

29
Q

what effect does MHC class 1 binding site being closed off have

A

class 1 MHC can only hold short peptides

30
Q

which type MHC can hold short peptides

A

class 1 MHC can only hold short peptides

31
Q

what molecules can MHC class 2 bind to

A

class 2 MHC molecules can bind to peptides of different lengths because the binding site is open at both ends

32
Q

which MCHC molecule has a binding site open at both ends

A

MHC molecule class 2 has a binding site open at both ends

33
Q

what effect does an open binding site on MHC molecule have

A

MHC Class 2 has an open binding site at both ends, means that peptides of different (longer) lengths can bind

34
Q

what determines the number of peptides that can be recognised

A

the number of MHC alleles determines the number of peptides that can be recognised

35
Q

what does the number of MHC alleles determine

A

the number of peptides that can be recognised

36
Q

which type of MHC carriers are more disease resitant

A

MHC heterozygotes are more disease resistant

37
Q

what is the effect of being a MHC heterozygote

A

you are more disease resistant as it may increase the diversity of antigens resented to T cells, creating a diverse T cell repertoire

38
Q

why is it hypothesized that MHC heterozygotes are more disease resistant

A

MHC variants will have associations with specific pathogens - therefore less susceptible to disease

39
Q

which MHC alleles are associated with disease resistance

A

HLA alleles - infectious diseases

40
Q

what does MHC heterozygosity confer a selective advantage against

A

multiple strain infections

41
Q

what do MHC class 1 and 2 molecules do

A

they present peptide antigens to T cells, initiating immune recognition of foreign antigens

42
Q

name a disease that MHC hetrozygosity is effectively associated with

A

Hep B

43
Q

what experiments have been done to show MHC heterozygosity does confer disease resistance

A

Salmonella in MHC heterozygote mice

44
Q

what is the sexual selection hypothesis

A

females should prefer mates that produce favourable MHC genotypes for their offspring
- requires that females can know MHC type of potential mates and females maximize the heterozygosity of offspring

45
Q

which hypothesis states females should prefer mates that produce favourable MHC genotypes for their offspring

A

sexual selection hypothesis

46
Q

what is assortative mating

A

non random mating pattern in which individuals with similar genotype+/phenotypes mate with one another more frequently than would be expected under random mating

47
Q

what type of mating is mating where two individuals mate more than would be expected under random condns

A

assortative mating

48
Q

give an example of MHC-dependent disassortative mating

A

cycling women prefer the scent of MHC dissimilar men - but this wasnt the case for females on the pill

49
Q

discuss the T-shirt study

A

females significantly prefer the odor of T-shirts worn by MHC-dissimilar males, although such preference was not found among females taking the contraceptive pill

50
Q

what is the upsuck study

A

female orgasms help retain sperm by sucking it up into the uterus

51
Q

how does sharing MHC alleles affect time to conception

A

sharing MHC alleles increases time to conception

HELENP EE Evolution and Natural Selection (14 decks)

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