Sex and Reproduction Flashcards
1
Q
Costs of sexual reproduction
A
- loss of 50% genes
- energetic cost of producing gametes
- time & energy invested in courtship & mating
2
Q
Asexual reproduction species
A
- New Mexico whiptail
- some invertebrate animal species
- some fish, amphibians, reptiles
3
Q
Benefits of sexual reproduction
A
- offspring more varied
- mutations reduced
4
Q
Isogamy
A
identical gametes
microorganisms
5
Q
Anisogamy
A
different gametes
most plants & animals
6
Q
Why two sexes?
A
- Sexual reproduction X require (only needs gametes)
- Small gametes (sperm): increased probability of encountering & fertilizing large gametes
- Large gametes (eggs): can carry more nutrients & resources
7
Q
Why is the sex ratio typically 1:1? (Fisher)
A
- Frequency-Dependent selection acting upon the individual
- female dominated –> advantage to produce males
- male dominated –> advantage to produce females
- a female-biased sex ratio X evolutionarily stable
8
Q
Alligator sex determination (Ferguson & Joanen)
A
- temp of egg determines sex of offspring during 2nd & 3rd week of incubation
- 30 C below –> all females
- 34 C above –> all males
- ~32 –> lean females
9
Q
Red deer (Clutton-Brock)
A
- maternally-sub sons less reproductive success than maternally-dom
- daughters equal reproductive success regardless of maternal dominance
- hypothesis: natual selection might favor ability to adjust progeny sex ratio in relation to parents’ ability to invest in offspring (dominance = more resources for offspring)
10
Q
Cameron (2004) (more on the red deer shit)
A
- mothers in good condition have more sons
- higher uterine glucose levels favor the development of males
- reveals a potential mechanism for sex-ratio variation in relation to maternal condition around conception
11
Q
Viviparous mite
A
- mom produces brood of 1 son & ~20 daughters
- son mates w/ sisters inside & dies before born
- no selfish mutants for rare sex to take advantage (limited by environment)
12
Q
“Ideal” (optimal) mating systems
A
- male acquires as many mates as possible & invests little in parental care
- females select “fit” male & leaves parental duties to him while acquiring resources required to produce more offspring (female is more “selective” sex)
13
Q
Bateman Effect
A
- as mates increase, mean # of offspring increases for males increases; stays the same for females –> no advantage to increasing mates EXCEPT genetic diversity
- mean # offspring range much wider for males than females
14
Q
Moulay Ismail
A
- Emperor of Morocco
- 548 sons & 340 daughters in his harem of 500 women during his life (~1.2 copulations/day for 62 years)
- unlikely due to following factors:
- ovulation frequency combined w. sperm survival (women fertile only 12.5% of time)
- female infertility
- conception likelihood
- prenatal mortality
15
Q
Mating systems
A
- Polygyny (male w. multiple females) –> baboon, safe grouse, elk
- Promiscuity (both sexes have multiple partners) –> Japanese macaques, bonobos
- Polyandry (female w/ multiple males)–> seahorses
- Monogamy (1 male, 1 female) –> only ~5% of species
16
Q
Ecological factors influence how animals are distributed in space
A
- Polygyny –> small groups of females
- Promiscuity –> large groups of females or lack of male dominance
- Polyandry –> male reproductive output limited by time/energy constraints or female behavior
- Monogamy –> environmental demands require both male and female input for offspring survival
17
Q
Polygyny types
A
- Female defense polygyny: males directly defend several females from other males (greater spear-nosed bat, elk, lions)
- Resource defense polygyny: males w/ multiple females that are attracted to resources under his control (polygyny threshold model) (red-winged birds)
- Lek polygyny: multiple females attracted to male display territory (topi bulls, hammer-headed bat, leaf-cutting ant)
- Scramble competition: male acquires multiple widely scattered mates by being the first to encounter them (horseshoe crab, 13-lined ground squirrel)
18
Q
Polygyny threshold model (lark buntings)
A
- shade important to keeping nestlings cool
- females may choose a “polygynous territory” of a male” w/ good shade cover of a “monogamous territory” w/ less shade, even if the polygynous male restricts aid in rearing nestlings to first female
19
Q
Cock-of-the-rock
A
- Lek Polygyny
- males assemble in dozens & squabble amongst themselves
- female spotted –> males spread out & claim plot of land –> try to persuade female to land next to him by competitively bouncing
- peck neck –> chosen –> immediate fornication
- female will lay eggs alone
- another female may choose same male
- increases chance of displaying to females even in few actually mate
20
Q
Scramble competition polygyny
A
- female usually mates once
- males X need to display or compete
21
Q
Jacana
A
- 1 female, male harem
- female guards territory, need male to watch over nests
- ~4-5 nesting males
- predation stresses female in protecting eggs –> recruit males to help + increase in female size to produce more eggs
22
Q
Sexual selection (first proposed by Darwin)
A
selection for traits that are attractive to mates/ traits that concern competition for mates
subdivision of Darwinian selection that concerns mating
23
Q
Long-tailed widow bird (Andersson)
A
- females preder longer tails even if diff performance areas are weaker
- dangerously low flights & jumping competitions (in other widow bird species)
23
Q
Intersexual selection
A
- involves exaggerated traits that one prefers in the other
- ex. sage grouse, magnificent frigate bird: puffed chests
- ex. bats: male perfumes scent onto female, female chirp to determine male fitness
24
Q
Bower birds
A
males w/ more decorations @ nest get more females (tend to match colors)
25
Q
Sexual selection hypotheses
A
- “Runaway” selection (Fisher)
- Disease/parasite avoidance (Hamilton & Zuk)
- Handicap principle (Zahavi)
26
Q
“Runaway” selection (Fisher)
A
- tail length increases due to combination of both survival advantage & female choice
- optimal tail length for survival heightened largely due to female choice
- what else promotes a certain trait to “run away” & succeed? –> female choice
27
Q
Female sticklebacks
A
- use male coloration to identify healthy mates and avoid parasite-infected males
- brighter red males chosen
- effect disappears under green light
28
Q
European blackbirds (Biard)
A
- eating foods w/ carotenoids results in darker beaks –> more sexually attractive to females
- plant pigments: involved in antioxidant activity & conversion to vitamin A –> increased perceived immune system health
29
Q
House finches (Oh & Badyaev)
A
- duller-colored males more appealing by being more social prior to mating season
- by mating season, less attractive male have = success as brightly colored males
30
Q
Disease/parasite avoidance hypothesis (Hamilton & Zuk)
A
some traits signal good health
sticklebacks, house finches, European blackbirds
31
Q
Handicap principle (Zahavi)
A
cost of the trait assumed is cannot be faked by lower-quality males –> effective mechanism for secual selection
32
Q
Results of intrasexual selection on males
A
- guarding behavior
- sperm plugs
- biochemical substances that reduce female receptivity
- low threshold for mating attempts
- monopolization of females
- postponement of mating attempts
- “sneak” copulations
- forced copulations
- sexual interference
- female mimicry by males
- assaults on male competitors
- assaults on offspring of competitors
- size of testes
33
Q
Guarding behavior
A
- damselfly: similar to dungflu copulation guarding; use appendage to hold onto female
- lovebugs: 56 hour copulation tie
34
Q
Sperm plugs
A
- green anaconda
- dragonfly: barbs & flagella allow for 2nd male to remove sperm of first
- primates: penile morphologies - adaptations for sperm removal?
- orb-weaving spider: male self-destructs during mating –> corpse remains wedged in female
35
Q
Biochemical warfare that reduce female receptivity
A
- Postman butterfly: during copulation, male deposits scent into female that makes her unattractive to other males
36
Q
Low threshold for mating attempts
A
- Cock-of-the-rock: presented w/ opportunity –> male proceeds quickly
37
Q
Postponement of mating attempts & “sneak” copulations
A
- Baboons: sub males may wait for mating opportunity when alpha male unaware
38
Q
Forced copulations
A
- Scorpionflies: courtship –> female reject –> male use appendage to grasp onto female & mate –> female may try to escape
- Orangutans
- Ducks: some female ducks’ vaginas spiral in opposite direction of male phallus & longer (species w/ fewer forced copulations tend to have shorter & simpler genitalia)
39
Q
Female mimicry
A
- Garter snakes: late male may represent self as female via pheromones
- Sticklebacks: non-territorial male behaves like female –> allowed into territorial male’s nest –> may deposit sperm into female instead of actual male
- Western marsh harrier hawk: female-like males may access breeding resources while avoiding costly fights w/ typical territorial males (fem hawks attacked & attack less, may be adaptive)
40
Q
Size of testes
A
- Primates: tend to be relative to body weight
- Yellow-toothed cavy
- Bushcrickets: largest testes to body-ratio –> deposit only small amounts of sperm/mating –> likely for mating w/ many females vs. competitively intrasexually
41
Q
The Evolution of Animal Weapons (Emlen)
A
- tendency for weapons to begin small –> more ornate
- smaller = more damaging (only role to attack other males)
- more elaborate = less injury/death (use as signal to females/ritualized combat)
