Sexual Selection (3) Flashcards
(115 cards)
1
Q
Sexual selection?
A
= the preference by one sex for certain traits of the other sex which explains the evolution of male secondary sexual traits & female preferences.
2
Q
Sexual selection in basic terms?
A
Where there’s a choice made by the opposite sex.
3
Q
Sexual selection attributes? (4)
A
• Special case of natural selection.
• Focuses on traits that enhance the ability to attract mates & reproductive success.
• Traits are counteracted by natural selection.
• Works in conjunction with natural selection.
4
Q
What does sexual selection involve?
A
Non-random variance in reproduction.
5
Q
How is SS playing a role in mating systems?
A
6
Q
SS forms? (2)
A
• Intra-SS.
• Inter-SS.
7
Q
Intra-SS?
A
= SS/competition that occurs within a sex (mostly males) for fertilization.
8
Q
Intra-SS types? (2)
A
• Pre-copulatory (individual fighting).
• Post-copulatory (sperm competition).
9
Q
Intra-SS: Pre-copulatory?
A
= individual fighting/Male-Male competition.
10
Q
When we talk about sperm competition & success what do we mean?
A
We mean that successful males often have to have better sperm, ie. more sperm, bigger sperm = more mating success.
11
Q
Inter-SS?
A
= SS that results from female choice where females mate preferentially with males that have exaggerated traits.
12
Q
What do we mean by “cryptic female choice”?
A
That females choose sperm packets that are healthier, favourable & produce healthy offspring.
13
Q
Pre-copulatory vs Post-copulatory SS regarding consciousness?
A
● Pre-copulatory = conscious.
● Post-copulatory = unconscious.
14
Q
Why is Inter-SS: Post-copulatory unconscious?
A
It is because the female is not really eliminating & picking sperm packets based on her preference but she’s only seeking for those sperm packets with more protein & nutrients.
15
Q
Why do males compete & females choose?
A
Bateman’s principle.
16
Q
Bateman’s principle attributes? (3)
A
That males often exhibit:
• more variance in reproductive success.
• more variance in mating success.
• Therefore, reproductive success depends on mating success.
17
Q
What paradigm further explains the Bateman’s principle?
A
Darwin-Bateman paradigm.
18
Q
Darwin-Bateman paradigm components in order? (4)
A
• Anisogamy.
• SS.
• Parental care.
• Sexual dimorphism.
19
Q
2 concepts that pop up when answering why SS acts stronger on males?
A
• Sexual dimorphism.
• Parental care.
20
Q
Anisogamy?
A
= Gamete variation between sexes.
21
Q
Basic way to understand what anisogamy means?
A
Not the same gametes.
From:
• Aniso = not the same.
• Gamy = gametes.
22
Q
Where is gamete variation seen?
A
In males & females.
23
Q
Female gametes attributes? (3)
A
• Large.
• Few.
• Energetically expensive (well-provisioned).
24
Q
Male gametes attributes? (3)
A
• Small.
• Many (millions).
• Energetically cheap.
25
What are the consequences of anisogamy? (2)
• Sexual dimorphism.
• Parental care.
26
Sexual dimorphism?
= differences in morphology (sometimes physiology) between males & females of the same species.
27
Selection criteria for combat in males? (3)
• Large body size.
• Great strength.
• Weaponry.
28
Ways that males compete? (5)
• Fighting & ritualized contests.
• Food item packets.
• Sperm packets.
• Sneaky fake gifts.
• The Ultimate Sacrifice, themselves.
29
If you can't compete, then what?
Be sneaky.
30
Eg of organism where we question whether a body part is a weapon or ornament?
Narwhals.
31
Are females choosy?
Absolutely!
32
Why are females choosy? (3)
• Resource acquisition (direct benefits).
• Genetics (indirect benefits).
• Sexy sons.
33
What do we mean by resource acquisition?
We mean that the female benefits directly via having food, protection (from harrassment from other males) & shelter.
34
What do we mean by genetics?
We mean that the female indirectly benefits via all offspring benefiting from the good genes from the potential mate.
35
Eg of good genes?
Three spine stickleback.
36
Handicap principle?
= principle that proposes that females prefer males with handicaps/whacky traits because handicaps are indicators of heritable viability & survival.
37
Eg of animals species that practice Handicap principle?
Springbok.
38
Sexy sons principle?
= principle where the female focuses on the quality of the male offspring via the father's traits which are remarkable among males.
39
Sexy sons primarily focuses on what?
The remarkable traits of the male.
40
Which types of selection maintain variation? (2)
• Disruptive selection.
• -FDS.
41
What 2 types of SS relate to evolution/co-evolution?
• Runaway SS.
• Chase-away SS.
42
How are 3 ways that trait variation is maintained in a population?
* Mutations.
* Quantitative traits.
* Variation in female choice over time.
43
Eg of inter-SS of Pre-copulatory?
Seen in The Paradise bird.
44
Eg of inter-SS of Post-copulatory?
In female snakes.
45
What is Runaway SS?
= sexual selection for traits that don't contribute to survival of the male organism but increases the reproductive success of the male possessing them.
46
What is the main message/point that the Bateman's principle is trying to say?
That the variance in mating success is generally greater among males.
47
What is the primary reason to females being choosy in sexual selection?
Being choosy may increase or decrease the chances of survival in her male offspring.
48
Where do the direct benefits to female arise from?
Her preference.
49
Where do the indirect benefits to females arise from?
Arise from the benefits to her offspring.
50
What do females prefer in a male to mate with? (3)
• Bright colours.
• Enlarged, ornamented traits.
• Showy males.
51
Results of Intra-SS?/What does intra-SS lead to? (4)
• Combat.
• Sperm competition.
• Alternative male reproductive strategy (sneaky males).
• Infanticide.
52
Results of inter-SS?/What does inter-SS lead to? (3)
• Elaborate colouration.
• Courtship behaviour.
• Exaggerated 2ndary male characteristics.
53
What does SS depend on?
The advantages of individuals over each other of the same sex & species in reproduction.
54
Chase-away SS?
= antagonistic co-evolution between sexes where the traits of one sex is harmful to the other & results in the fitness of the other sex declining.
55
Sexual selection role?
Enhances reproductive success.
56
Natural selection role?
Enhances survival.
57
Difference between sexual selection & natural selection?
● SS = enhances reproductive success.
● NS = enhances survival.
58
Sexual selection =...?
Mate attraction.
59
Natural selection =...?
Predation.
60
SS vs NS experiment attributes? (3)
• Guppies (Poecilia).
• Laboratory selection studies.
• John Endler.
61
Explain SS vs NS experiment?
● To test NS, Guppies were put in a tank with coarse sediment at the bottom. A predator was added into the tank. Eventually, it turned out that guppies that acquired/mimicked the coarse pattern of the sand/sediment survived predation and survived compared to guppies that didn't. On the other hand, when fine sediment was placed, guppies that mimicked the fine sediment survived predation and were the fittest.
● To test SS, female & male guppies were placed in the tank along with coarse sediment/sand. Male guppies that contrasted the pattern of the sediment attracted more mates/females than those that mimicked the coarse background, thus increasing their reproductive success. The opposite occurred when a fine sediment was added.
62
Conclusion of SS vs NS experiment? (2)
• NS favours spot patterns that match the background.
• SS favours male patterns that contrast the background.
63
What should you consider when NS & SS act simultaneously?
Consider the costs vs the benefits of survival & mate attraction.
64
Intra-SS: Post-copulatory?
= sperm competition with sneaky male present.
65
Inter-SS types? (2)
• Pre-copulatory (female choice).
• Post-copulatory (cryptic female choice).
66
What do we mean by "SS traits are counteracted by NS"?
NS pressures will eventually outrun/outweigh those of SS.
67
Egs of competition in less conspicuous ways under Post-copulatory mechanisms? (3)
• Copulatory plugs.
• Hypodermic insemination.
• Anti-aphrodisiacs.
68
Copulatory plugs?
= where the male seals the reproductive tract of the female to prevent her from remating.
69
Eg of organism that uses copulatory plugs?
Male parasitic worms.
70
Hypodermic insemination?
= where the male pierces the female's abdomen with his aedeagus & injects his sperm through the wound into her abdominal cavity.
71
Eg of organism that practices Hypodermic insemination?
Hemipteran insects.
72
Anti-aphrodisiacs?
= when the male uses his semen/deposits his semen, which contains antiaphrodisiacs, into the female he recently mated with to repel other males from mating with the female.
73
Eg of organism that uses Anti-aphrodisiacs?
Male plant bugs (Lygus hesperus).
74
Why do females mate with more than one male? (3)
• Cost of resistance.
• Material/Direct benefits.
• Indirect benefits.
75
Egs of Cost of resistance? (2)
• Harrassment.
• Infanticide.
76
Thing to note on Infanticide?
Males with a sufficient chance of paternity won't commit infanticide.
77
Explain the Material/Direct benefits?
It means that females will have access to more resources.
78
Eg of organisms that use Material/Direct benefits?
Dragonflies.
79
Explain how females indirectly benefit from mating with more than one male?
Through fertility insurance which decreases the risk of having infertile partners.
80
Eg of organism under Indirect benefits?
Female prairie dogs.
81
Thing to note regarding the form of SS?
The form of SS is directly related to relative investment in offspring production.
82
Bateman's principle?
= states that the sex that invests more in offspring production has fewer reproductive opportunities.
83
Bateman's principle conclusion?
Sex with the higher investment is choosy.
84
Explain the graph: Why males are competing for females & females choosing?
Females' reproductive success increases by how much investment is put in offspring.
85
What illustrates the consequences of anisogamy?
The Darwin-Bateman paradigm.
86
Anisogamy in terms of Darwin-Bateman paradigm?
= female biased prezygotic investment.
87
SS in terms of Darwin-Bateman paradigm?
= SS acts stronger on males.
88
Parental care in terms of Darwin-Bateman paradigm?
= female biased post-zygotic investment.
89
Sexual dimorphism in terms of Darwin-Bateman paradigm?
= elaborated trait expression in males.
90
Why does SS act stronger on males?
SS acts stronger on males because their fitness is limited by their access/exposure to females. Therefore, they are under a lot of pressure to impress female mates to carry & transfer their genes to their offspring & increase their fitness/reproductive success.
91
What is the basis of SS?
Anisogamy.
92
Egs of animals in Fighting & Ritualized context? (3)
• Giraffes.
• Male red deers.
• Lyre birds.
93
Eg of animals in Food items?
Birds.
94
Eg of animals in Sperm packets?
Grasshoppers.
95
Egs of animals in The Ultimate Sacrifice? (2)
• Praying mantis.
• Male black widow spiders.
96
Egs of organisms that choose to be sneaky instead of competing? (2)
• Side-blotched lizard.
• Cuttlefish.
97
Conclusion of the experiment testing if females are choosy?
There was increased treatment in males with more elongated tails.
98
Organisms used in the experiment testing if females are choosy?
Long-tailed widowbirds.
99
Narwhals attributes? (3)
• Have insightful incisors/tantalizing tusks.
• Tusks aren't used for weapons.
• Tusks are ornaments.
100
What do we mean when we say that good genes are an indirect benefit?
That females focus only on the offspring quality through her ensuring that the male possesses favourable traits like strength.
101
Hypotheses that explain the good genes? (2)
• Handicap principle.
• Sexy sons.
102
Egs of organisms under Resource acquisition? (3)
• Parental care in fish (roles).
• Male bullfrogs.
• Augrabies flat lizards.
103
Explain good genes example?
Where female sticklebacs prefer males with red bellies as red bellies means that they are well nourished & have good immune systems.
104
Difference between Godd genes vs Sexy sons?
● Good genes = focuses on the quality of all offspring.
● Sexy sons = focuses on the quality of sons.
105
What does the Sexy sons hypothesis leads to?
Fisher's runaway model.
106
Fisher's runaway model?
= states that a female prefers more longer tails which then makes the male trait more exaggerated.
107
Evidence of females choosing for sexy sons?
Males with bright red colour shouldn't show high viability just increased mates.
108
Evidence of females choosing good genes? (2)
• Bright red = carotenoids in diet = healthier.
• Subordinate vs Dominant males (where the latter is able to retain the red colour for long even in mating seasons unlike the former males).
109
How is trait variation maintained? (3)
• Mutations.
• Quantitative traits.
• Variation in female choice over time.
110
Sexual conflict over mating on the males side?
Because they need to have as many mates as possible (increased matings), there seems to be a need for aggression.
111
Sexual conflict over mating on the females side?
Since they need to choose the best partner, they see the need to resist mating.
112
How do you have sexual conflict over mating?
Because the males have more matings, they see the need for aggression & the females need to choose the best partner & see the need to resist mating, it causes a SS arms race where they both impose selective pressures onto each other & thus evolve abilities in response to each other.
113
Other instance where sexual conflict over mating exists?
Predator-Prey interaction.
114
Egs of sex role reversal? (2)
• Seahorses.
• Pipefish.
115
Hypotheses explaining sex role reversal? (2)
• Males are better at taking care of offspring.
• Males are less likely than females to find a mate.
