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ISCI 350 > Sexes > Flashcards

Sexes Flashcards

1
Q

isogamy (2)

A
  • different mating types (+/-) have same sized gametes

- most unicellular organisms

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2
Q

anisogamy (2)

A
  • females and males with different sized gametes

- most multicellular organisms

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3
Q

evolution of female anisogamy

A
  • females evolved to have large gametes that provide resources for development
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4
Q

evolution of male anisogamy (2)

A
  • competition to fertilize large gametes favoured production of many small gametes
  • males who invest less energy and produce more offspring have better chance of fertilizing large egg
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5
Q

sexually antagonistic selection

A
  • selection is pulling in 2 different directions according to male and female gametes (big and small)
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6
Q

female gametes (2)

A
  • few large gametes

- females invest more in each offspring than do males

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7
Q

male gametes (2)

A
  • many small gametes

- males invest less in each offspring than females do

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8
Q

is it better to be female/male?

A
  • not more beneficial to be either: both have different limitations
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9
Q

cascading effects of anisogamy

A
  • sexual selection

- sexual conflict

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10
Q

do males/females have greater variance in reproduction success (2)

A
  • males have greater variance in reproductive success than females
  • females are limited by the number of offspring they can invest in while males can essentially have unlimited offspring due to smaller investment
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11
Q

does mating more increase offspring production in males/females (2)

A
  • males: mating with more females increase the number of offspring they produce; beneficial for men to reproduce more often
  • females: mating with more males does not increase offspring number; not beneficial for females to have more mates
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12
Q

mating system

A
  • monogamous or polygynous

- intensity of sexual selection and conflict with depend on mating system

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13
Q

monogamous systems effect on conflict

A
  • less conflict
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14
Q

polygynous systems effect on conflict

A
  • greater conflict
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15
Q

“choosy parent” (2)

A
  • determined by the sex whose typical parental investment is greater
  • this sex is the limiting resource for the opposite sex and becomes more choosy of her mating partner
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16
Q

sex role reversal (2)

A
  • seahorse or giant water bugs

- here, females compete for males and males are choosy

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17
Q

sexual selection factors

A
  • female choice

- male-male competition

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18
Q

cause of sexual selection

A
  • females are limited by the number of offspring they can produce
  • increases with monogamous mating systems
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19
Q

cause of sexual conflict/male-male competition

A
  • males are limited by the number of females willing to mate with them
  • increases with polygynous mating systems
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20
Q

sexual selection

A
  • different selective force from NS and goes against NS as it tends to decrease organism fitness
  • responsible for evolution of exaggerated male traits
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21
Q

components of male-male competition (3)

A
  • pre-copulatory
  • post-copulatory
  • post-fertilization
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22
Q

male-male competition: pre-copulatory mechanisms (2)

A
  • territorial defence (guarding areas where females emerge)

- combat

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23
Q

male-male competition: post-copulatory mechanisms (2)

A
  • mate guarding: non contact or contact guarding to avoid sperm competition
  • sperm competition: 2nd male mate can displace sperm of 1st male mate
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24
Q

male-male competition: post-fertilization mechanisms

A
  • infanticide: males kill infants so females will be able to mate again sooner
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25
Q

inter-organism sexual selection forces

A
  • the essence of maleness and femaleness

- male-male competition

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26
Q

intra-organism sexual selection forces

A
  • males make themselves more attractive to appeal to female choice
27
Q

“sexy son” or “good looks” hypothesis (2)

A
  • females choose the best looking males so the father’s sons will also be attractive and preferred as mates
  • trait continues to evolve until it becomes so exaggerated that it hinders male survival
28
Q

sexy son hypothesis

- assumptions (2)

A
  • exaggerated trait must be heritable

- female preference must be open ended

29
Q

sexy son hypothesis

- prediction

A
  • exaggerated trait and female preference should become associated
30
Q

“good genes” hypothesis

A
  • females use exaggerated traits to assess male genetic quality
31
Q

“good genes” hypothesis

- assumption

A
  • there is an association between “good genes”/fitness and exaggerated traits
32
Q

“good genes” hypothesis

- predictions (2)

A
  • exaggerated trait must be costly (to indicate that its other genes are truly good)
  • fitness must be heritable to both daughters and sons
33
Q

balance between NS and sexual selection (3)

A
  • observed male traits are usually above optimum tale length (is NS was acting alone)
  • initially: good genes hypothesis takes fitness to peak of curve, then sexy son hypothesis pushes fitness to lower fitness
  • equilibrium observed trait present at point where NS and SS are equal
34
Q

sexual selection in humans: female choice (2)

A
  • female features may be shaped by male mate choice instead

- 2D mating environment disfavours female choice

35
Q

sexual selection in humans: male-male competition (2)

A
  • 2D mating environment favours contest competition
  • male traits appear to increase appearance of dominance over other men rather than being perceived as more attractive by other women
36
Q

what items do sexes often disagree on (4)

A
  1. multiple matings
  2. mating decisions
  3. offspring care
  4. infanticide
37
Q

description of sexes disagreement: multiple matings

A
  • unlike males, females tend to gain little by mating more
38
Q

description of sexes disagreement: mating decisions

A
  • females would lose more by mating with low quality males
39
Q

description of sexes disagreement: offspring care

A
  • both sexes would benefit by leaving the offspring in care of the other
40
Q

description of sexes disagreement: infanticide

A
  • when it occurs, females loose their reproductive investment
41
Q

conflict between sexes: concealed ovulation (3)

A
  • absence of visual signs of ovulation
  • some species ovulation is advertised during short estrous periods while others ovulation is hidden
  • females are sexually receptive at times when conception is not possible, but males are not, leading to non-reproductive mating events
42
Q

concealed ovulation: father-at-home hypothesis (3)

A
  • males do not know when other females are wandering and are discouraged from wandering
  • stay home to ensure fertilization of partner, guard her from other males
  • result: father stays home to help with care of offspring he can be reasonably sure are his
43
Q

concealed ovulation: father-at-home hypothesis

- mating system encouraged

A
  • monogamous mating system
44
Q

concealed ovulation: many-fathers hypothesis (2)

A
  • by mating opportunistically, a female lower the probability of her offspring being killed by males who are unsure of their paternity
  • confuses paternity
45
Q

concealed ovulation: many-fathers hypothesis

- assumed/encouraged mating system

A
  • undoes monogamy and assumed polygamy

- expected to have evolved in multi-male troops or harems

45
Q

concealed ovulation: many-fathers hypothesis

- assumed/encouraged mating system

A
  • undoes monogamy and assumed polygamy

- expected to have evolved in multi-male troops or harems

46
Q

concealed ovulation: comparative study results (3)

A
  • slight ovulatory signs and multi-male mating systems ancestral to anthropoid primates
  • ovulatory signs have lost 0-1 times under monogamy and 8-11 times un multi-male/harem systems
  • monogamy evolved independently 7 times, always in lineages with no or only slight ovulatory signs and never in lineages with bold advertisement
47
Q

concealed ovulation: comparative study meaning (2)

A
  • loss of ovulatory signs in multi-male and harem systems is consistent with many-fathers hypothesis
  • concealed ovulation and monogamy are associated, but monogamy seems to have been facilitated by concealed ovulations (concealed ovulation -> monogamy)
48
Q

genomic imprinting (2)

A
  • epigenetic inactivation of one of the two alleles at a locus depending on parent-of-origin
  • parent-specific pattern of methylation established during gametogenesis is inherited, but does not involve changes to underlying DNA sequence
49
Q

genomic imprinting results

A
  • haploid expression of some genes, thus potentially unmasking deleterious recessive alleles and lowering fitness
50
Q

where is genomic imprinting seen (3)

A
  • mammals, seed plants, some insects
51
Q

imprinted genes

A
  • usually involved in placentation and transfer of nutrients between mother and offspring
52
Q

meaning of patterns of imprinting

A

may reflect conflicts between mother and father, and between mother and offspring

  • father activates genes that extract more resources from the mother
  • mother deactivates genes that will allow extraction of resources to counter father’s activated genes
53
Q

result of patterns of imprinting

A
  • parental tug-of-war in the developing embryo
54
Q

Angelman syndrome (3)

A
  • imprinting error due to excess of paternal imprinting
  • child’s signals tend to stimulate maternal investment: prolonged suckling, frequent crying, hyper-active/sleepless
  • high rates of autism
55
Q

Prader-Willi syndrome (3)

A
  • imprinting error due to excess of maternal imprinting
  • child’s signals tend to decrease maternal investment: poor suckling, weak crying, inactive/sleepy
  • high rates of psychosis in adults
56
Q

why has genomic imprinting evolved

- hypotheses (3)

A

non-mutually exclusive hypotheses:

  • ovarian-time-bomb hypothesis
  • mechanism of post-zygotic isolation
  • parent-conflict hypothesis
57
Q

genomic imprinting: ovarian-time-bomb hypothesis

A
  • GI evolved to protect female mammals from spontaneous development of unfertilized eggs, which may lead to cancert
58
Q

genomic imprinting: mechanism for post-zygotic isolation (2)

A
  • diverging imprinting patterns across closely related species may serve to prevent development of inter-specific hybrids
  • patterns are species specific so that mating between different species will cause zygote to fail and hybrid to not be produced
59
Q

genomic imprinting: parent-conflict hypothesis

A
  • GI is the result of conflict between maternal and paternal genes in species with multiple paternity
60
Q

genomic imprinting: parent-conflict hypothesis

- paternally expressed genes (2)

A
  • maximize growth of fetus by maximizing extraction of resources from the mother
  • attempts to enhance offspring and paternal fitness
61
Q

genomic imprinting: parent-conflict hypothesis

- maternally expressed genes (2)

A
  • tend to conserve resources to divide them among more offspring
  • attempts to maximize lifetime reproductive success of the mother and decrease that of the individual father
62
Q

genomic imprinting

- mating system (2)

A
  • strong in polygynous species where fathers want more resources for own offspring
  • weak in monogamous species where fathers want equal investment to each offspring
63
Q

genomic imprinting: prenatal parental investment and mating system (2)

A
  • more investment in polygynous systems reflect war between mother and offspring (more extraction of resources due to paternal imprinting)
  • less investment in monogamous systems as imprinting is weaker

ISCI 350 (14 decks)

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