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APS 209: Animal behaviour > 7: evolution of sex > Flashcards

7: evolution of sex Flashcards

1
Q

what can gametes either be?

A

large and female

small and male

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2
Q

what is the evolutionary origin of the 2 sexes?

A

ancestral state: gametes were equal size and any gametes could come together

  • then a mutant will small gametes arises
  • gamete specialisation evolved
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3
Q

if we assume mutant gametes are half the size and can make twice as many then when will and when wont the mutant do better?

A

yes- if survival of smaller embryo is >50% of normal embryo

no- if survival of smaller embryo <50% of normal embryo

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4
Q

when looking at the graphical model for size and survival of embryo what does a steeper dotted line tangent mean?

A

greater pay off in terms of survival

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5
Q

when looking at the graphical model for size and survival of embryo what is the tangent?

A

size of embryo that maximises survival (values of x and y on the curve) per unit mass

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6
Q

when looking at the graphical model for size and survival of embryo when are half sized gametes favoured?(3)

A
  • when half sized gametes fuse with normal they produce 3/4 sized embryos
  • twice as many half sized gametes give more offspring
  • if the survival curve is favoured
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7
Q

when does the advantage of smaller gametes decrease?

A

as gets more common and fusion is random

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8
Q

what happens if 2 small gametes fuse?

- how is this avoided?

A

embryo will only be half size

- small gameted evolve ability to avoid fusing

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9
Q

what does sperms ability to not fuse to other sperm lead to?

A

evolution of 2 sex system

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10
Q

what is sperm competition?

A

competition between sperm of two or more males inside the females reproductive tract

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11
Q

why do males engage in sperm competition?

A

to maximise chance of fathering offspring

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12
Q

how do male damselflies engage in sperm competition?

A

elaborate penis used to remove sperm of rivals before inseminating female

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13
Q

in terms of sperm production how do polyandrous male insects compare to monogamous?

A

polyandrous males produce higher proportion of viable sperm

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14
Q

what is the Adelie penguin example of sperm competition?

A
  • males strategically allocate sperm to females

- monogamous males engage in sperm competition by extra pair copulations

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15
Q

what do some males do to ensure their mate doesn’t have an extra pair copulation? + example

A

mate guarding to protect paternity

male magpie and zebra finch both follow mate during her fertile period

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16
Q

what do seychelle male warblers do prior to fertile period and what is this period?

A

4 days prior to egg laying and copulations in this period could fertilize egg
- lots of extra pair copulation attempts

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17
Q

what do seychelle male warblers do during female fertile period?

A

will mate guard to reduce number of extra pair copulation attempts

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18
Q

what happened to seychell male warbler behaviour if a fake egg was placed in the females nest 4 days before egg laying?

A

switched off mate guarding and led to a spike in number of intrusions and successful extra pair copulation attempts

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19
Q

what do male milkweed beetles often do to stop other males mating?

A

stay mounted on the female

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20
Q

in an experiment by Dickson on milkweed beetles what was done? and what % of separated males and females found new mates and what are the implications of each of these?

A
  • mate guarding males removed from females
  • 25% separated males found new mate in 30 mins -> guarding resulted in missed mating opportunities
  • 50% females found new mate after male removal -> guarding prevents females from remating
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21
Q

when is guarding beneficial to the milkweed beetle male?

A

if last male to copulate fathers 40% or more of females offspring so gains more from guarding, such as more offspring, rather than searching for new mates

22
Q

when is guarding not beneficial to the milkweed beetle?

A

when last male fathers <40% as wont father as more offspring

23
Q

what do male fulmar birds do to protect their paternity and why? (2)

A
  • copulate over 50 times with partner to outcompete other male sperm
  • increases chance of inseminating when she is most fertile
24
Q

what does frequent copulation ensure?

A

optimal timing of insemination relative to fertilisation

25
Q

what is cryptic female choice?

A

female manipulation of sperm inside her reproductive tract so a prefered male fertilises her eggs

26
Q

what did Pizarri and Birkhead find in 2000 for sperm ejection in chickens and what is this an example of?

A

cryptic female choice

- females eject sperm from cloaca of low ranking subordinate males and accept the sperm of dominant males

27
Q

what is sperm ejection in dunnock birds? (3)

A
  • before copulation male often pecks females cloaca if another male been near
  • causes her to eject fluid droplet
  • looks like ejecting sperm but droplet contain inviable, broke, tangled sper
28
Q

which sex is in control in hanging flies?

A

female

29
Q

describe nuptial gifts and sperm acceptance in hanging flies (3)

A
  • female eats the gift during sperm transfer which usually lasts 20 minutes
  • only males providing large gifts >20mm will have full sperm transfer
  • if not large enough copulation will end before all sperm is transferred
30
Q

why do females engage in cryptic female choice, what do they gain and how?

A

gain:

  • higher quality offspring by cryptically choosing high quality fathers
  • more offspring by cryptic choice of genetically compatible males
31
Q

how do males that are unsuccessful in competition and are not chosen by females achieve reproductive success? - what are the 2 examples?

A

alternative mating strategies

  1. alternative are not equally rewarding
  2. alternatives are equally rewarding
32
Q

in terms of the small, medium and large males what are the alternative male tactics in scorpion flies?

A
  • large- guard dead insects attractive to females and gain 6 matings each
  • medium- produce cheap salivary gifts to attract females which are less attractive + 2 matings each
  • small- force copulations on females + 1 mating each
33
Q

in scorpion flies what happens if the large males are removed?

A

medium sized males now adopt large males tactics as no longer trying and failing to compete with it

34
Q

what is the fitness of the scorpion fly alternative tactics?

A

unequal fitness

35
Q

what are the 3 male morphs in isopods and what do they all have?

A
  • alpha/fighter
  • beta/female mimic
  • gamma/hider
    different genotypes with genetically determined differences and different advantages in terms of mating
36
Q

shuster and wade studies isopods in 1991 what did they find about how the morphs behaved? (3)

A
  • alpha meeting gamma will throw it away as is dominant
  • gamma will hide and sneak copulations
  • beta male will mimic females so alpha wastes time trying to court it
37
Q

shuster and wade studies isopods in 1991 what did they find for what frequencies the morphs occur at and the fitness and success of the alternative strategies?

A
  • occur at frequencies at which their fitness is equal

- equal fitness and reproductive success

38
Q

which isopod fathers the most offspring when:

a) alpha and beta males and 1 female
b) alpha and beta males with multiple females

A

a) alpha

b) beta as alpha struggled to copulate with them all

39
Q

in terms of large, medium and small males what are the alternative male tactics in bluegills?

A
  • large-produce nests attractive to females
  • medium- have female colouration and slip between territorial male and mate during spawning
  • small- lay low to slip between
40
Q

in blue gills which males father the most offspring + % comparison of this?

A

territorial large males:98.7%

1.3% for small and medium males

41
Q

what is the most important act in the life of any animal? and what is an indicator of this?

A

passing on genes

- the wide variety of behavioral strategies to achieve reproduction

42
Q

what is an adaptive gne often linked to?

A

one affecting mate preference - are on 2 linked loci

43
Q

what is the paradox of sex?

A

inefficient, complicated, time consuming, difficult, dangerous, costly

44
Q

twofold cost of sex assumes males only contribute genes- how can they increase their reproductive output?

A

male parental care

45
Q

what are the 2 models used for how short term cost of sex is overcome to generate long term benefits?

A

1 . genetic drift/mullers ratchet

2. red queen hypothesis

46
Q

what is Geoff parkers hypothesis for the evolution of anisogamy based on?

A

disruptive selection

  • selection for the smallest and the largest
  • as individuals have a fixed budget for reproduction so can only be one or the other
47
Q

which sex competes for the other?

A

one investing least competes for one investing most

48
Q

what does the graphical model of size of embryo and survival show overall?

A

how selection could favour a mutant individual invading, that produces twice as many half sized gametes

49
Q

how may males that cant guard their mates for ecological or social reasons protect their paternity?

A

copulating frequently with their partner

50
Q

what did Pizzari and Birkhead discover for sperm ejection in domestic fowl?

A

females will eject sperm of subordinate males and accept sperm of dominant male

APS 209: Animal behaviour (25 decks)

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