Reproduction Flashcards
1
Q
What are the two elements of sex
A
Gametogenesis
Fertilisation
2
Q
What is gametogenesis
A
the production of haploid sperm and eggs via meiosis. Involves recombination and isolation of one set of chromosomes.
3
Q
What is fertilisation
A
Fusion of haploid gametes from two different individuals to produce diploid embryos / offspring
4
Q
When did recombination/ sygamy first evolve
A
3 billion years ago
5
Q
When did sexual reproduction evolve and what does that mean
A
1.2 billion
selected early on in evolution of ‘life’ = advantageous phenomenon
6
Q
What percentage of eukaryotes use sex
A
99%
7
Q
Why did sex use to provide an evolutionary problem
A
because cloning (embryogenesis) was simpler,, faster cycle and greater reproductive rate
8
Q
What is the two fold cost of sex
A
Sexual females 1) have to produce sons, and 2) share reproduction with another individual
9
Q
If an asexual population coexisted with a sexual population (all other things equal) what would happen
A
Asexual females can grow exponentially , and thus rapidly out compete the sexual population
10
Q
What are the 5 costs of sex
A
Production of males that can't produce themselves Sharing genetic reproduction Break-up of co-adapted gene complexes Requirement to locate mates/sperm Sexual conflict
11
Q
What are the two themes for explanationing for the evolution of sex
A
DRIFT MODELS (Fisher-Muller Hypotheses) SELECTION MODELS (Red Queen Hypotheses
12
Q
Explain Muller’s Ratchet (drift model)
A
Asexual lineages accumulate mutations
Mutations are usually deleterious
Only back-mutations (very rare) can purge mutations
therefore Sex helps to break the ratchet – e.g. combining 2 individuals carrying both one copy of a deleterious mutation will mean that at least 1 in 4 offspring produced free of the mutation
13
Q
Evidence for drift models
A
Evidence shows that most asexual tax persist only for a short evolutionary time, they do not persist as lineages
14
Q
Example of species which supports drift models
A
The hybrid fish had lower parasite load than either of the parent species of topminnow
15
Q
What is the red queen hypothesis (selection model)
A
Keep running to stand still
Selection gradients are strong and vary in time and space
e.g Host-Parasite or Predator-Prey co-evolution
Sex allows for more rapid evolutionary change/ adaption
16
Q
What are the two benefits of sex (or why do males exist)
A
- Sex undoes the unidirectional costs of mutation accumulation
(=dump bad genomes) - Sex allows offspring variability to combat co-adapting competitors (e.g. parasites) (=spread good genomes)
17
Q
What is the benefit of being diploid
A
Diploid cells and more resistant to DNA damage through things such as UV
18
Q
What is the cost of being diploid
A
Lower reproductive rate when compared with haploid cells
19
Q
What is endomitosis
A
internal mechanism for self chromosome doubling/halving
20
Q
What did selection for alternating haploid-diploid cycles depend on
A
depended on probability of DNA damage
21
Q
What is syngamy
A
the fusion of two cells, or of their nuclei (e.g gametes), in reproduction to form a diploid unicell (rather than endomitosis).
22
Q
How did anisogamy evolve?
A
Early aquatic sexual reproduces would produce isogamous protogametes that would undergo haploid syngamy. However there was variation in protogamete size which eventually lead to anisogamy
23
Q
What kind of evolution did protogametes undergo
A
disruptive selection
24
Q
What two strategies could protogametes take
A
Be large, rare and fecund
Be small, common but not very fecund
25
evidence relationship between egg size and offspring fitness
Bigger eggs in Murres =
Earlier fledging
Faster wing feather development
Higher weight maintenance after fledgling
in Brook Trout
Bigger eggs = bigger juvenile size at hatching, higher offspring survival.
26
What is the relationship between sperm competitions and sperm number
The greater the sperm competition (promiscuity) the more sperm is produced
27
Why will eggs always be big and sperm small ie why is anisogamy an evolutionary stable strategy
sperm =0.01% volume investment of ova
Doubling sperm volume = insignificant increase - to 0.02% - of zygote investment
But halving of ejaculate size = significant loss of ~50 million sperm cells
Anisogamy is therefore stable as increased sperm volume does not contribute to zygote fitness, but has significant losses for sperm numbers / male fitness
28
How does risk affect sperm production, give example
Both rats and birds have been shown to change how much they invest into their sperm production dependent on the risk. If they is a high probability that the female hsa mated with another male, they invest more than if there is a low chance the female has mated with another male
29
What is Bateman's principle
in most species, variability in reproductive success (or reproductive variance) is greater in males than in females due to anisgomay, sperm are cheaper than eggs.
30
It terms of reproductive fitness, what are males constrained by
The amount of females he can mate with
31
It terms of reproductive fitness, what are females constrained by
The amount of offspring she can reproduce
32
What are the 3 points of Bateman's principle
1. male reproductive success increases with the no of mates they attempt to copulate with, not the same for females
2. Male reproductive success will show more variance than females
3. sexual selection will have a greater effect on the sex with greater variance in reproductive success
33
What is the effect of parental care on reproductive rate
It constrains is
34
What are two forms of polygyny
Lekking and harems
35
What are the characteristics of monogamy
One male mates with one female
Associated with biparental care
Social V genetic monogamy (EPCs)
90% of bird species
36
Why are emperor penguins monogamous
Tough Antarctic env needs both sexes to engage in rearing offspring so males become more limiting and so there is less male-male competition
37
What mating pattern do most birds follow
Many birds are socially monogamous,
| but extra-pair copulations occur
38
What are the characteristics of polygyny
```
One male mates with several females
Usually without paternal care
Usually overt male:male competition
Sometimes sneak/satellite males
Often associated with male-biased sexual size dimorphism
```
39
What is a lek
are organised displays of male secondary sexual traits
| for females to choose from – usually biased success to few males
40
Example of extreme reproductive skews in leks
```
White bearded manakin: Lek with
22 males and 437 matings
1st male achieved 328 matings (75%)
2nd male achieved 56 matings
All other ~20 males achieved
53 matings
```
41
What are the characteristics of polyandry
One female mates with several males
With or without paternal care or mutliple males offering care
Generates sperm competition
Common and can occur within social monogamy
42
Example of polyandrous species
Honeybee and harbour porpoise
43
Characteristics of polygamy/promiscuity
Many males mate with many females
No pair bonds formed
Uniparental/parental care uncommon
Common in non-bird/mammal taxa
44
Example of polgamous species
Rhea (one of the fewbirds)
| Blanket spawning fish
45
How does spatial ecology affect mating patterns
Widely spaced females =
constrained to monogamy
Aggregated females =
potential for polygyny?
46
What did Emlen and Oring argue about ecology and sexual selection
Ecological constrains impose limits on the degree to which sexual selection can operate
47
What is the relationship between mate monopolisation and intensity of sexual selection
The greater the potential for multiple mate monopolization, the greater should be the potential intensity of sexual selection and the tendency for polygamy
48
How does temporal distribution affect the trend for polygamy
If individuals are highly clumped due to resources not being evenly distributed, there is the opportunity for a few individuals to monopolise the resources and thus increase competition and thus polygamy
49
What is the relationship between aynschrony and polygamy
as aynschrony increases, so does the level of pplygamy
50
Why does synchrony lead to monogamy
If all female are fertile at the same time, it is difficult to monopolise, particularly if their fertility window is short and mating takes a long time
51
What is the difference between sexually selected traits and naturally selected traits
Sexually selected traits do not help the individuals survival
52
Evidence that sexual selection increases extinction risk
Bro‐Jørgensen found that bovoid extinction risk increased with antler size
53
3 reasons why sexual selection occurs
Bateman principle
Potential reproductive rate variance
Parental Investment
54
How does parental investment effect sexual selection
the sex whose typical parental investment is greater than that of the opposite sex will become a limiting resource for that sex, thus the force of sexual selection will be on the other sex
55
What is the operational sex ratio
ratio between sexually active / receptive males:females
or… the ratio between females ready to mate and males ready to mate
or... the opportunity for sexual selection
56
What is the primary sex ratio
The sex ratio at birth,often 1:1
57
What is the secondary sex ratio
The sex ratio once in adult hood ( e.g richardson's ground squirrel has a secondary sex ratio of 1:5-10 as male disperse from the colony and become more vulnerable)
58
What is intra sexual selection
When individuals of the same sex compete for mates (aka an intersexual result)
59
What are direct benefits of females selecting for
Conspecific recognition
To gain more parental care (Territory,incubation,defence, food)
Fertility assurance
60
Why is conspecific recognition important
to avoid less fertile/infertile hybridisation
61
What is the realtionship between alloparty, sympatry and mate choice
It was shown in drosophila, species that had evolved in sympatry had developed the ability to discriminate between potential sexual partners faster than pairs evolved in allopatry
62
What is nuptial feeding
When food items or inedible tokens are transferred to females by males during courtship or copulation (direct benefit of SS)
63
Example of nuptial feeding
Bush crickets provide an edible spermatophore which the females ingest into their reproductive tract. The size of the it positively influences the females refractory period and the males reproduction success
64
Why do male redback spiders sacrifice themselves to females (andrade, 1996)
Males benefit (greater percentage of paternity) by mating with a female for longer. Females benefit from extra meal, males indirectly feed their own offspring. This strategy may have evolved since males suffer extreme mortality risks while mate-searching – 80% of males do not encounter a mate
65
Example of a courtship relating to fertiity
There is a positive relationship between Trinidadian guppy's amount of signoids and thrusts and the amount of sperm he produces
66
Reason why monogamous birds had extra pair copulations (with example)
House sparrows are more likely to mate with other males if their primary male has low fertility and has not fertilised all her eggs
67
Evidence for that indirect benefits exist
Partridge 1980 breed 100 females with a partner they couldn't choose and 100 wit one though could. The offspring fitness was then measured under standardised conditions competing to grow and survive against marker flies. Chosen offspring significantly out competed the marker flies
68
What are the 4 sexual selection model
Runaway SS
Good genes
Parasite mediated
compatible genes
69
Why came up with the runaway selection model
Fisher 1930
70
What is the runaway selection model
Females prefer a particular (naturally selected/ arbitrary) trait
There is a genetic link between male trait and female preference
Sons who carry that trait are successful
Traits fix in population and female genes for trait choice persist
Runaway exaggeration of the trait
71
Who put forward the good genes model
Zahavi 1975
72
What is the good genes model
Traits are costly to develop/ carry they are a handicap
Carrying the handicap is an honest signal of individual male quality
Handicap is either a standard and acts as a survival filter or
it is condition dependent and better males carry bigger handicaps
Being fathered by males that can carry the handicap will capture better genes
73
Who put forward the parasite mediated model
Hamilton and Zuk (1985)
74
What is the parasite mediated model
Parasite load is a major and general problem
Signal is linked to parasite resistance
Being fathered by males with evident signals will capture better resistance genes
75
Correlation evidence for runaway selection
Houde and Endler 1990
Male ornamentation varies across different populations of Trinidadian guppies
They found, after studying 7 different population, that naive females preferred their own populations males ornamentation
= Evidence that female preference genes co-evolved with male trait
76
Experimental evidence of runaway selection
In stalk eyed flies there is male dimorphism in eye stalk length. Males with bigger eye stalks win in competition for resources and mates. Wilkinson and Reillo 1994 artificially selected to increase and decrease male eyespan in different lines and then test female preference for that ‘short’ or ‘long’ eye span males. Unselected females and selected 'long' females preferred long eye stalk males, whilst short females preferred short eyed males.
= Evidence that female preference genes experimentally co-evolved with male trait expression
77
Evidence for good genes
At Whipsnade zoo peafowls were paired with males with different tail eye spot traits. Sons and daughters grew bigger when fathered by males carrying bigger eyespots
Chick groups sired by big-eyed fathers had better % survival in Whipsnade Park
78
What is the major histocompatibiity complex and why is it important in SS
A complex that allows for the immune system to recognise foreign pathogens. The more diverse it is, the better it works to recognise a foreign pathogen. Therefore females will try and mate with those with a different MHC to them to increase their offspring parasite and disease resistance
79
Evidence that heterozygosity at the MHC confers an immune advantage in mice
Penn et al 2002 found that heteroygoys mice had higher growth under pathogen challenge and better survival
80
Why does sexual selection occur
Occurs due to divergence in potential reproductive rate, OSR & parental investment
81
What is sperm competition
the competition within a single female between the sperm from two or more males over the fertilization of the ova
82
Selection arising from sperm competiton is a product of
Polyandry =how many males
might enter the competition
Sperm longevity = how likely sperm will compete
83
Why is sperm competition very strong in insects
Most insects store sperm from multiple males so evolution is acting hard in their reproductive tracts
84
What are the two main strategies males take to deal with sperm competition
avoid sperm competition
| enhance the success of self sperm
85
What is mate guarding?
When a male protects there mate from other males to increase paternity
86
What is the trade off with mate guarding
By mate guarding you increase the chance of parenting the offspring but prevents you from mating with other females
87
What did Carroll 1993 find out soapberry bug populations and sperm competition
Natural soapberry bug populations show plasticity in male mating/guarding duration depending on risk of sperm competition from OSR i.e. when there were twice as many females to males copulation time was shorter than when there were 3 times as many males to females
88
What is proxy guarding
When a male makes a plug that prevents other males mating with the female
89
How do cannibalised male red back spiders have greater reproductive fitness
May mating for longer and commiting suicide, male redback spiders fertilise more eggs and females are less likely to remate than males who survive
90
Example of males using antiaphrodisiac
Male postman butterflies insert beta-ocimene , an antiaphrodisiac pheromone, into females which in turn repels other males from mating Schulz et al 2007
91
example of rival sperm removal
The ancient greenling has 2 stags of copulation
males remove part of the stored sperm with scarpers on their secondary genitalia, and inseminate during the second stage, at the end of mating. Can be 100% effective
92
How does sperm competition affect testes size (examples)
Primates and yellow dung flies both show males having larger testes when there is more sperm competition/ polyandry than when in monogamous societies
93
As sperm competition gets higher, what should happen with sperm size
it should get smaller
94
What happens to sperm size when under intense sperm competition example
Godwin et al 2017 evolved flour beetles in lab for 77 generations under either female biased OSRs (=low sperm competition) or male-biased OSRs (=high sperm competition Male-biased OSRs became more competitive… And their sperm got bigger/better quality
95
Why is sperm velocity selected for in sperm competition example
In mass spawning situations, fast sperm are more likely to find the eggs first and father more offspring
96
What is sperm polymorphism
When a male produces different types of sperm
97
Example of sperm polymorphism
Male green veined butterflies produce two types of sperm, apyrene and eupyrene. Apyrene sperm acts as ‘cheap filler’ in female storage and signals to the female not to remate
98
Example of sperm cooperation
Wood mice sperm have little hooks which allow them to link and swim in chain which increases their speed, getting to egg before rival
99
How long is Drosophila bifurca sperm
58.3 mm
100
How long is Drosophila bifurca sperm
58.3 mm
101
Why is sperm gigantism an advantage in fruitflies
longer sperm are really good at displacing their competitors from the female reproductive tract, which gives them an advantage in the competition for fertilization. It also shows quality, only healthy large males can produce large sperm
102
Relationship between female fruit fly reproductive tract length and sperm length
When female tracts are longer – long-sperm males did better
103
What is cryptic female choice
Female-mediated morphological, behavioral, or physiological mechanisms that bias fertilization toward the sperm of specific males’
104
In what kind of reproductive relationship mechanism thing does cryptic female choice occur
Polyandry
105
What is the problem with CFC
DIFFICULT to dissect apart male effects from female choice because often females benefit from being fertilised by the ‘best’ males
e. g Why might males with big antlers win more fertilisations?
1. CFC for males carrying big antlers?
2. Males with big antlers have more competitive sperm?
106
When do we expect to find greater evidence for CFC
if females are at risk of being fertilised by males too close or too distantly related and this is where studies have taken place
107
6 potential opportunities for cryptic female choice
Disrupt successful copulation / insemination
Differential sperm transport
Differential sperm storage
Differential sperm rejection
Differential sperm-egg compatibility
Selective ovulation / oocyte / embryo reabsorption
108
Example of females disrupting insemination
Hens were found to be more likely to eject sperm of low ranking cocks than high
109
How did Tregenza and Wedell (2002) show cyrptic female choice in two spotted crickets
They mated females with 2 brothers = inbreeding depression and two unrelated = high proportion of eggs hatching. They then mated females with sib+non and non+sib. Results showed that they avoid the low egg viability associated with sibling matings so must have a mechanism that allows them to choose the non sperms
110
How do salmon and trout show CFC
The ovarian fluid around the eggs causes the sperm of the same species to swim straighter when it touches it, making ti more likely to successfully fertilise the correct egg
111
When does sexual conflict occur
When the reproductive aims of males and females do not unite
112
What are the types of sexual conflict
Direct conflict - harassed by too many males
Genetic conflict - harassed by non preferred males
Indirect conflict - costs arising from male:male competition e.g male lions killing cubs
113
What drives the strength of sexual conflict
The potential reproductive rate difference e.g if rates are closely aligned, then conflict is less intense
114
What are the costs of mating
Wasted time
Predation/abiotic risks
Injury or trauma
Parasite transmission
Disruption of reproductive pair bonds (risk of desertion etc)
Costs arising from male:male competition adaptations
115
What is the Trivers-Willard Theory of sex allocation
Because males usually have higher reproductive potential and variance than females, better conditions should favour investment in sons to enable realisation of that potential
116
Example of Trivers-Willard Theory of sex allocation
Red deer on the Isle of Rhum fit the model – higher socially-ranking hinds produce more sons as it will increase their increase their reproductive fitness
Clutton-Brock 1984
117
Example of sex ratio adjustment experiment
lesser black-backed gulls had their maternal condition manipulated, upward = supplementary feeding
downward = induced extended egg laying by removing eggs
Supplementary feeding maintained even sex ratio
No supplementary feeding shifted bias to females
118
Example in intense level of sibling rivalry
Sand tiger sharks have their teeth fully developed before they are born, and if they develop first they will eat their siblings
119
How does relatedness affect sibling rivalry
In nests with a high level of extra pair parentage, begging loudness is greater . But this is a costly behaviour because the louder you beg, the more likely a predator is to find you
120
How does extra pair paternity affect chick mouth colour
The more distantly related a clutch is, the brighter and redder the mouths, example of increased begging intenisty
121
Example of siblicide
Masked boobies always lay two chicks, the second being an insurance chick. The biggest always kills the other suggesting the optimum clutch size is one
122
Why does polyandry increase sibling rivalry
It further reduces genetic relatedness between siblings, decreasing the influence of kin selection
123
What is the evolutionary paradox of cooperative breeding
Individuals helping other individuals to reproduce, at a cost to themselves. Contradicts the idea that individuals should maximise their own reproductive
success!
124
How is brood helping condition dependent in meekats
Only help when above threshold weight
Short term cost – lose weight
Stop helping when drop below threshold
No reduction in survival
125
What is kin selection
An individual can increase the number of copies of
| its genes in future generations by helping to increase the reproductive success of close relatives (W.D Hamilton 1964)
126
Why do vertebrate cooperative breeding systems evolve in terms of group living
Ecological constraints - individuals join a group - or don’t leave their natal territory - because there are no good breeding opportunities available and
Benefits of philopatry
Increased survival
Increased chance to inherit territory
•Ability to safely look for breeding opportunites
127
What are the benefits of helping raise others offspring
indirect - kin selected benefits
| direct - - increase an individuals own lifetime reproductive success
128
What is the cooperate breeding arrangement of Seychelles warblers
Dominant pair with subordinates, normally females
129
Explain the monogamy hypothesis
Based on Hamilton's Rule, for altruistic acts c
