EE Lecture 6: Sexual Selection

Question 1

define sexual dimorphism

Answer 1

phenotypic differences between males and females of the same species

Question 2

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

Answer 2

sexual dimorphism

Question 3

define sexual selection

Answer 3

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

Question 4

what does sexual selection favour

Answer 4

any heritable trait that increases reproductive success

Question 5

what is Bateman’s principle

Answer 5

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

Question 6

what is Triver’s theory

Answer 6

theory of parental investment

Question 7

what are females reproductive rates limited by

Answer 7

the number of offspring they can birth in a lifetime

Question 8

whate are male reproductive rates limited by

Answer 8

number of females they can impregnate

Question 9

which sex invests greater in offspring

Answer 9

females

Question 10

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

Answer 10

males

Question 11

which sex are more choosy

Answer 11

females

Question 12

why is there variance in reproductive success

Answer 12

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

Question 13

what are male strategies for reproductive success

Answer 13

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

Question 14

under what circumstances will males invest in offspring

Answer 14

if parent certainty is high

Question 15

what are female strategies for reproductive success

Answer 15

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

Question 16

what is Fisher’s hypothesis

Answer 16

runaway selection hypothesis

Question 17

who thought of the runaway selection hypothesis

Answer 17

Fisher

Question 18

what is Fisher’s runaway selection hypothesis

Answer 18

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

Question 19

what is Fishers runaway selection hypothesis halted by

Answer 19

natural selection

Question 20

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

Answer 20

Fishers runaway selection hypothesis

Question 21

what is Zahavi’s hypothesis

Answer 21

Zahavi’s handicap hypothesis

Question 22

what is Zahavis handicap hypothesis

Answer 22

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

Question 23

what is the MHC

Answer 23

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

Question 24

how many bp is the MHC

where is it found

Answer 24

3.6Mb region on short arm of chrom 6

Question 25

what does MHC encode

Answer 25

immune system proteins

Question 26

what is the function of the MHC

Answer 26

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

Question 27

how many types of molecules do MHC makes

Answer 27

class 1 and class2

Question 28

what can class 1 MHC molecules hold - why

Answer 28

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

Question 29

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

Answer 29

class 1 MHC can only hold short peptides

Question 30

which type MHC can hold short peptides

Answer 30

class 1 MHC can only hold short peptides

Question 31

what molecules can MHC class 2 bind to

Answer 31

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

Question 32

which MCHC molecule has a binding site open at both ends

Answer 32

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

Question 33

what effect does an open binding site on MHC molecule have

Answer 33

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

Question 34

what determines the number of peptides that can be recognised

Answer 34

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

Question 35

what does the number of MHC alleles determine

Answer 35

the number of peptides that can be recognised

Question 36

which type of MHC carriers are more disease resitant

Answer 36

MHC heterozygotes are more disease resistant

Question 37

what is the effect of being a MHC heterozygote

Answer 37

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

Question 38

why is it hypothesized that MHC heterozygotes are more disease resistant

Answer 38

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

Question 39

which MHC alleles are associated with disease resistance

Answer 39

HLA alleles - infectious diseases

Question 40

what does MHC heterozygosity confer a selective advantage against

Answer 40

multiple strain infections

Question 41

what do MHC class 1 and 2 molecules do

Answer 41

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

Question 42

name a disease that MHC hetrozygosity is effectively associated with

Answer 42

Hep B

Question 43

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

Answer 43

Salmonella in MHC heterozygote mice

Question 44

what is the sexual selection hypothesis

Answer 44

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

Question 45

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

Answer 45

sexual selection hypothesis

Question 46

what is assortative mating

Answer 46

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

Question 47

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

Answer 47

assortative mating

Question 48

give an example of MHC-dependent disassortative mating

Answer 48

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

Question 49

discuss the T-shirt study

Answer 49

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

Question 50

what is the upsuck study

Answer 50

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

Question 51

how does sharing MHC alleles affect time to conception

Answer 51

sharing MHC alleles increases time to conception