Chapter 8: Reproduction Flashcards
(39 cards)
Female reproductive strategies
- ova
- investment
- mating
Limits to number of ova and offspring
Limits to age of fertility
Heavy investment in pregnancy and nurturance (choosy with males –want males w best traits so offspring have best survival chance)
Generally more cautious, as mating in wrong conditions can be costly (food storage, extremely hot/cold climate, lack of shelter)
Want to select optimal mate, but not always able
Male reproductive strategies
- sperm
- investment
- mating
Sperm are numerous
Less required investment (in production and in caregiving)
Effort may end at insemination
Multiple matings propagate genes (mate with as many mate as possible, not choosy)
Intense competition with other males
Males Issues
Paternity confidence (risk of cuckoldry)
Bonding usually requires confidence
Intermale competition (fighting for access for females, stronger=better genes)
Infanticide (males will kill offspring that are not his own)
r
growth rate of population
K
carrying capacity of environment (probability of survival)
R-selected species (high r, low K)
• Large number of offspring • Little investment • Short juvenile period • Low offspring survivability EX: sea turtle, fruit flies, fish, insects
K-selected species (low r, high K)
• Small number of offspring • Heavy investment (mostly from the mother) • Prolonged juvenile period • Higher offspring survivability EX: larger mammals, humans
Monogamy
one male and one female, lifelong
More dominant males lose reproductive potential
Lower status males gain reproductive potential
More dispersion of reproduction across all types of males
Female-female competition for dominant males
Serial Monogamy
repeated 1 male and 1 female partnerships, limited duration
More dominant males lose reproductive potential
Lower status males gain reproductive potential
Female-female competition for dominant males
Polygamy
Multiple pairings by both males and females
Polygyny
Multiple pairings by one male and several females
Dominant males gain Lower status males excluded Intermale competition intensified Lower status females access successful males Competition among co-females
Polyandry
Multiple pairings by one female and several males
Rare –Males often tied by kinship
Lower status females lose reproductive potential
Reduced infanticide
EX: bees (queen bee), humpback whales
Promiscuity
no exclusive partnerships
Female choice
Disease risk high
Paternity uncertainty, thus males often do not bond/care for young care
Polyamory
more than 1 partner in a relationship
Unique to humans (everyone in the group is consenting) –trust, emotional bond b/w individuals
Considered either a relationship practice OR sexual orientation
Male-Female Bonding
Advantages
Decreased disease risk
Bi-parental care more effective
Higher quality offspring
Female gets assistance, provisioning, defense
Male-Female Bonding
Disadvantages
Exclusion of other opportunities
Partner may not be fertile
Possibility of deception by partner
Male: sexual infidelity by female (cuckoldry)
Female: male may abandon / neglect / abuse
Male Sexual Behaviour
mounting, intromission, ejaculation
Mounting: positioning on the female to permit copulation
Intromission: insertion of the penis with pelvic thrusting
Ejaculation: reflexive emission of sperm
Male Basic Spinal Reflexes
Erection – parasympathetic NS
Ejaculation – sympathetic NS
L1, L2 (SNS) and S2/3/4 (PNS)
Damage to spinal cord above lumbar –both erection & ejaculation can still occur
Damage to spinal cord above sacral –erection can occur, ejaculation cannot
Male Sex Hormone Synthesis
Hypothalamus–>GnRH–>Pituitary Gland–>LH (Leydig cells in testes–>testosterone) & FSH (Sertoli cells in testes–>inhibin)
Hormones and Male Sexual Response
- testosterone levels
- experiment w Rhesus monkeys
- arousal
Testosterone levels highest in the morning, decrease throughout the day (similar to cortisol)
Levels vary among males (at any given time during the day)
Castration reduces male sexual response, but not always (adrenals and experience)
Experiment:
- Intact (still had testes): 75% of time ejaculation occurs
- Castrated: 15-20% of cases had ejaculation initially, increased to 50-55% when injected with dihydrotestosterone (more successful mating)
o Maintained testosterone levels =better reproduction success
Male arousal facilitated by minor increases in general arousal and catecholamines
Male arousal dampened by major stress, fatigue, and over-arousal
Shafik (1996)
Underwear experiment
Materials containing polyester caused erectile disfunction in the 12 months of wearing the pants, recovers after removing pants
Greater electrostatic potentials in the polyester-containing groups –higher friction b/w underpants and genitals =erectile disfunction
Female Sexual Behaviour
reflexes, proceptivity, receptivity
Reflexes: spinal (e.g. lubrication, blood flow, lordosis)
Proceptivity: extent which a female will elicit copulations as reflected by her behaviour
- Anal-genital sniffing, push themselves underneath the male, bit at their neck
Receptivity: female’s state of responsiveness to sexual initiation by male
• Female sexual reflexes generally inhibited by stress & stress hormones
• Facilitated by parasympathetic NS
Female Basic Spinal Reflexes
Lubrication, blood flow, lordosis (arched back)
Female sexual reflexes generally inhibited by stress and stress hormones
Facilitated by PNS
Female Sex Hormone Synthesis
Hypothalamus–>GnRH–>Pituitary Gland–>LH (->estrogen) & FSH (–>inhibin)
