Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Evolutionary Biology > Sex, Cooperation and conflict > Flashcards

Sex, Cooperation and conflict Flashcards

1
Q

What is sex?

A

The occurrence of meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Under the meiosis definition of sex, what 3 things are assumed?

A

Sex does not require separate sexes

Sex is not necessary for reproduction

Sex is not the same as reproduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the paradox of sex?

A

Sex must confer some sort of fitness benefit or it wouldn’t be so pervasive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

The cost of sex

A

Takes a long time

Risk of reproducing maladapted offspring

Cost of mating (finding a mate, sexually transmitted diseases)

Loss of half of reproductive output (2-fold cost of sex)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the two fold cost of sex?

A

When producing sexually a female must combine her offspring with a male and thus loses 50% of her gene copies.

when producing asexually she has a 2-fold advantage of passing of two copies of her genes

all asexually produced offspring are female

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Time difference between yeast reproducing asexually and sexually ?

A

Asexually - 90mins

Sexually - several days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The cost of males (2-fold cost of sex)

A

The clonal offspring of an asexual female multiplies at twice the rate of the progeny descended from a sexual female

a sexual female has only 50% of the fitness of an asexual female

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is asexual selection favoured more in stable environments?

A

Sex is costly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is background selection?

A

Selection against strongly deleterious mutations

Fixation of weakly deleterious mutations

Accumulation of deleterious mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to an asexually producing population under background selection?

A

The population gets weaker in time due to lack of chromosome mixing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Stochastic loss

A

Random loss

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Muller’s ratchet

A

Stochastic loss of mutation-free chromosomes within a population

leads to an accumulation of deleterious mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Muller’s ratchet in an asexual population

A

Cannot be revered within an asexual populations

Leads to fitness decline over generations

Accumulation of deleterious mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Genetic hitchhiking

A

Deleterious mutations accumulate because they are linked to beneficial mutations

Selection for strongly beneficial mutations

Hitchhiking of linked deleterious mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Genetic hitchhiking in asexual populations

A

Recombination could de-couple but this cannot happen in asexual reproduction

beneficial and linked deleterious mutations are linked and cannot be separated

Accumulation of deleterious mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Ruby in the rubbish

A

Selection against strongly deleterious mutations

Elimination of linked beneficial mutations

Linked beneficial mutations cannot be de-coupled and so are lost

Less adaptation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The Hill-Robertson effect

A

Without recombination, fixation of beneficial mutations is much slower.

Selection is weaker without sex and recombination.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

benefits of sex - increased efficiency of selection

A

Benefit of the group not the individual

This does not fit with how we understand evolution

Evolution doesn’t have foresight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Benefits of sex - Generation genetically variable offspring

A

Advantageous in a variable environment

Red queen hypothesis - running to stand still

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are Facultative asexuals?

A

Organisms that can switch between sexual and asexual reproduction

Favours environmental change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Mud snail - parasite example (sexual/asexual reproduction)

A

Parasite causes castration of snail (complete fitness loss)

High levels of parasite numbers correlate with high levels of sexual reproduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Nematode example (free living and parasitic) - sexual and asexual

A

Parasitic form reproduce sexually to compete with changing host behaviour

Free living are much more stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is Isogamy ?

A

Same sized gametes (ancestral sexual state)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is anisogamy?

A

Different sized gametes

Balanced polymorphism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are mating types?

A
  • First steps in sex differentiation
  • Ensures gametes of same organism dont fuse
  • Promotes outbreeding
  • Mating types stop gametes fusing with gametes from the same organism (+/- equivalent to male/female)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Mating type examples

A
  • Chlamydomonas reinhardtii has two mating types (+/-)
  • Schizophyllum commune has thousands of mating types
  • Most common mating type is two (examples up to 10)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how did mating types evolve into sexes?

A

trade-off between size and number of gametes (large is more viable - small and many have more chances of fusion)

Medium gamete size = mediocre (selected against)

Disruptive selection leads to evolution of balanced polymorphism for gamete sizes (Anisogamy)

Large = egg = female
Small (and many) = sperm = male

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what makes zygote size

A

The sum of the gametes that fuse to form it

viability increases with size

zygote must be a certain size in order to be functional

positive relationship between zygote size and viability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Consequences of anisogamy

A
  • Sets up potential for sexual selection
  • Sexual selection is responsible for phenotypic differences between male and female
  • E.g. courtship behaviour, ornament (antlers etc), colouration etc.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Differential gamete investment

A

Males produce large quantities of gametes (individual gametes ‘cheap’ to produce)

Females produce fewer larger gametes (individual gametes are more costly)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

How do males increase their mating success?

A

Mate with many partners

success increases linearly with number of mates

Females don’t benefit from multiple matings (only one chance of fertilisation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is Bateman’s Principle?

A

Male mating success is more variable than female mating success

Females in most mating interactions are the limiting factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Why is male mating success more variable? (Bateman’s principle)

A

Males mating success is variable because they may or may not be allowed to mate

Females will always have the same mating success because they are the limiting factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What does Bateman’s principle lead to?

A

Variance leads to competition between males and choosiness of females

known as the parental investment theory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Parental investment theory

A

Variance leads to competition between males and choosiness between females

basis of sexual selection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Why are separate sexes not inevitable?

A

94% of flowering plants (angiosperms) are bisexual (have both male and female sex organs)

produce different sized gametes but fertilise themselves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Example of male variance in mating success

A

Rough-skinned newts: Females don’t benefit as much as males from mating with multiple partners

38
Q

Example of choosy males

A
  1. Sea horses
  2. Poison arrow dart frogs

Males show all parental care

females have multiple partners and males are choosy

39
Q

how does female choice incur a direct benefit?

A

Direct fitness increase

Choose a male that will directly provide resources to the female and her offspring

e.g.

Fertile or fecund males
Good parenting ability
Access to resources (food, nesting sites etc.)

40
Q

What does fecundity mean?

A

potential number of offspring that could be produced

41
Q

Direct benefits of female mate choice (mottled sculpin fish example)

A

males defend females eggs

females choose larger males

larger males have a higher proportion of hatchings

Direct benefit = parental care
Signal = larger size

42
Q

Examples of direct benefit of female mate choice

A

Nuptial gifts
- gifting a snack or something (better the gift more likely to mate) many insects and great grey shrike (bird).

Territory defence
e.g. male zebras defend watering holes - females benefit.

43
Q

Indirect benefit

A

Genetic benefit → choose the male that will provide genes to make fitter offspring

44
Q

Examples of indirect benefit

A

Bird of Paradise dance

no direct benefit to the female

Is a signal of good sperm

sign that male will produce fitter offspring

45
Q

Fisherian runaway selection model

A

Pick sexy traits to have sexy sons that get chosen by choosy females etc

Runaway selection

E.g. Swordtail fish - females love the sword

46
Q

Good genes model

A

Traits have evolved as an honest signal for males genetic quality.

Only males with good genes can afford to invest in the trait

47
Q

Example of good genes (stalk-eyed fly)

A
  • Larger stalks = honest signal of their good health
  • Study showing how different food eaten can cause variation in stalk length (poor nutrition - more chance of shorter stalks)
  • Male selection ornaments: Traits are often condition-dependent
48
Q

Sexual Vs. Natural Selection

A

Sexual selection can sometimes be costly and bad for survival

49
Q

Sexual Vs. Natural Selection Example (marine iguanas)

A

Galapagos marine iguana

Males are often much larger than optimum size (costly, often causes death)

Males attract females by defending territories (bigger body = better territory defence)

female choice is driving sexual selection to outweigh the survival cost

50
Q

What is sex determination?

A

Mechanisms that determine what sex a developing embryo ends up being

51
Q

What is the name for X&Y (as a sex-determining system?

A

Male heterogamety

e.g. humans, mammals, drosophila

52
Q

What is female heterogamety?

A

Z & W chromosomes

e.g. birds, butterflies

53
Q

Male heterogamety

A

X & Y chromosomes

XX = female
XY = male

54
Q

Why is Y a sex limited chromosome?

A

It only shows up in one of the sexes

W is a sex-limited chromosomes in a W&Z

ZZ = male
ZW = female

(There can sometimes be more than 2 chromosomes)

55
Q

In some animals, sex is determined by other triggers

A
  1. Sex determined by temperature

American alligator:
higher temp = males
lower temp = females

issue with climate change

  1. Social factors

blue banded gobi:
Sequencial hermaphrodites

remove male, largest female becomes male and takes over role

56
Q

what are sequencial hermaphrodites ?

A

Born one sex but have the ability to change sexes at some stage in their life

57
Q

sex determination in animals is incredibly diverse

A
  • XY sex chromosomes
  • ZW sex chromosomes
  • Haplodiploidy
  • Paternal genome elimination
  • Genetic sex determination
  • Environmental sex determination
  • Hermaphroditism
58
Q

Who discovered sex chromosomes?

A

Nettie Stevens

59
Q

Recombination suppression

A

Area on chromosome (strata) recombination is turned off

Older strata have fewer similar genes

Degeneration of the sex-limited sex chromosome

60
Q

what is recombination suppression?

A
  • Recombination suppression is key in the evolution of sex chromosomes, sex chromosomes are key drivers in sexual dimorphism and reproductive isolation.
  • Recombination has become suppressed between sex chromosmes.*
61
Q

What causes recombination suppression?

A
62
Q

Is recombination suppression a cause or a consequence of sex chromosome evolution?

A

Step in the process leading to the evolution of sex chromosomes

63
Q

Sex chromosome degradation - what is X-degenerate?

A

Relics of shared ancestry with X chromosome

64
Q

Sex chromosome degradation - what is ampliconic

A
  • Areas where there are multiple copies of the same gene
  • Many have testes-specific expression, suggesting they may be involved in spermatogenesis
65
Q

Sex-specific selection: in chickens

A

Chickens → intense female trait selection and relaxed female trait selection

W genes are convergently up or down-regulated

66
Q

Gene conversion on the Y (slowing degredation)

A

Non-reciprocal intra-chromosomal recombination

Palindromic regions
Human genome has 8 palindrome

Gene conversion from one copy to another

Preventing degeneration of important genes by having back ups

Not swap →is a copy

67
Q

Palindromic regions

Velcro

A

DNA sequence composed of two inverted repeats (arms) separated by a short spacer (can bind to one another like velcro)

causes a loop of dna

DNA can be exchanged within loop

68
Q

Gene movement onto the Y

A

Duplication of autosomal genes onto the Y chromosome

refreshing of genetic material to counter degeneration

69
Q

Divergent fitness optima

A

Fitness landscapes

Peaks and valleys of fitness landscapes dont always align between sexes

Different evolutionary interests

Drosophila show negative correlation between adult male and female but not with juveniles

70
Q

Types of sexual conflict

A
  1. Intra-locus conflict
  2. Inter-locus conflict
71
Q

Intra-locus conflict (definition)

A
  • Tug of war over trait with shared genetic basis
  • Conflict arises when a trait has a shared genetic basis (between males and females) and contradictory selective pressures act on the sexes.
72
Q

Inter-locus conflict (definition)

A

interacting traits on different loci

Trait within one sex interacts with trait in the other sex.

Conflict occurs over the outcome of the interaction between the sexes.

73
Q

Intra-locus conflict Drosophila body size example (sexual conflict)

A
  • Males want to be larger
  • females smaller
  • Due to the shared genetic basis of the trait expression overall size of males and females is in the middle
  • Unresolved conflict (tug of war prevents either sex from reaching their optimum size)
  • Compromise that doesn’t suit either sex
74
Q

How does intra-locus conflict effect diversity?

A

Can lead to balancing selection and elevated genetic diversity

Ongoing sexual conflict prevents purging of genetic diversity - instead it maintains it.

75
Q

Inter-locus sexual conflict examples

A

Drosophila mating:
Sex peptide → connects to sex-peptide receptor in female: Makes female less susceptible to future males & increases egg laying - good for males not good for females.

Bean weavils:
traumatic penis - spiny penis - ensures successful mating, injures female so she can’t mate again

Hard to resolved → leads to arms race between males penis structure and female evolve to reduce direct cost (kicking).

76
Q

Sexually concordant selection

A

→ alleles rise in population to fixation

77
Q

Sexually antagonistic selection

A

→ allele never fixed, maintained at

78
Q

What are the two routes for intra-locus conflict resolution?

A
  1. Sex chromosomes
  2. Gene expression on the autosomes
79
Q

Sex-Linkage (conflict resolution)

A

Genes on autosomes are exposed to male-specific selection 50% of the time and female 50%.

Dominant alleles on X should be more often selected for female-specific effects (because there are two x’s)

Recessive alleles on X should be more often selected for male-specific effects.

80
Q

Sex linkage prediction

A

The X chromosomes should be enriched for dominant female-benefit alleles and recessive male-benefit alleles.

81
Q

Mammalian X sex-linkage example

A

Prediction: X chromosomes is demasculinised (fewer dominant male-benefit alleles)

Evidence: Exodus of many testis-specific genes from the X chromosome to the autosomes in humans and mice

82
Q

Sex-linage: Z&W

A
  • Two Z chromosomes in males only one is females.
  • Prediction:
  • The Z chromosome should be enriched for dominant male-benefit alleles and recessive female-benefit alleles.
  • (opposite to mammals X&Y)
83
Q

Avian Z sex-linkage examples

A

Male wing patch on flycatchers - Map disproportionately to the Z chromosome

The Z chromosome is masculinised in chickens

84
Q

New sex chromosomes?

A

Prediction: there is a correlation between colour and the size of the recombination strata (recombination suppression) on the Y chromosome.

Convergent expansion of the non-recombining region in colourful populations - consistent with selection to resolve sexual conflict

85
Q

Resolving conflict: Gene expression.

A

gene expression can decouple male and female phenotypes and act to resolve conflict

86
Q

The difference between intra- and inter-locus conflict

A

Inter-locus conflict leads to an evolutionary arms race whereas intra-locus conflict leads to elevated genetic diversity through balancing selection

87
Q

How can intra-locus conflict be resolved?

A

By several routes

e.g. sex linkage, sex chromosome formation and sex-biased gene expression.

There is debate around the relative roles of these different routes

88
Q

Genomic conflict and sex

A
  • Genomic conflict arises more commonly in sexually reproducing organisms
  • Not all genes from one parent are inherited
  • Sex allows greater scope for genomic conflict
89
Q

Different levels of selection (genomic conflict)

A

Cells

Nucleus

Mitochondria

Cells and organelles show variation, reproduction and heredity so all subject to natural selection

90
Q
A

Evolutionary Biology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions