Social influence Flashcards
2 biological aims
- ensure your genetics are passed on
- ensure that the next generation is given every opportunity to succeed
what is sexual selection
selection of mates within the members of a sex and between the sexes
division of polygynous species
- male defends a harem
- males lek (defend a territory)
what is female reproductive success limited by
access to resources to develop eggs and raise offspring
what is male reproductive success limited by
access to female eggs
population sex ratio v operational sex ratio
population sex ratio of 1:1 is altered to the operational sex ratio because the limiting sex (females) can only mate when not gestating/lactating (males are competing sex)
fertility v fecundity
- fertility: the ability to produce young
- fecundity: fruitfulness, ability to produce many young
why do females choose
- best genetics for offspring (disease resistance, cope with environment, breeding success)
- best resources
- avoid exposing herself to disease
- paternal assistance with offspring care
when should females not be choosy
- population density is low
- too much energy or too dangerous to be choosy
types of visual cues in reproduction
- intersexual selection (mate selection): secondary sex characteristics to advertise fitness
- intrasexual selection (male competition): dominance hierarchy
types of olfactory cues in reproduction
- sending a notice: pheromones (secreted by female to attract male)
- intersexual selection (mate selection): inbreeding avoidance, MHC heterozygosity
- can determine health of potential mates
types of auditory cues in reproduction
- sending a notice
- intersexual selection (mates)
- intrasexual selection (dominance)
what is the whitten effect
- involves introduction of a novel male into a group of females
- females housed in groups often have suppressed cycles
- introduction of male overcomes this suppression, and the induced cycles are synched in a majority of females
whitten effect in sheep and goat breeding
- ram or buck effect
- used to hasten the entry of late anestrus ewes and does into the breeding season
- pheremones from buck/ram are responsible (produced under influence of DHT)
- female MOS and AOS detect signals –> go to KNDy neurons –> increases GnRH release
female ewes/does in ram/buck effect
- ones with well-developed follicles with experience LH surge in 24 hours, ovulate by day 3
- CL undergoes early luteolysis
- second ovulation 6-9days after –> then regular cycles
physiology behind female ewes/does in ram/buck effect
- follicles at first are of lower quality
- increased gonadotropins after male introduction
- lower quality CL –> reduced progesterone
- follicle growth –> increased estrogen
- premature onset of luteolysis
silent estrus in ewes and does
- ewes: first and often second are silent
- does: most silent in first, all show signs by second
- ewes need progesterone-priming to show estrus while does don’t
- ewes: lower progesterone not enough to prime them for second heat –> silent heats
the bruce effect
- rodent species
- when you expose an early pregnant female (prior to implantation) to a different male, her pregnancy will fail, and she will return to estrus
- explanation 1: pheromone in male urine increases dopamine release –> suppression of prolactin –> CL regresses
- explanation 2: testes of mice secrete estrogens –> excreted in urine –> absorbed into females via vomeronasal organ –> too much estrogen makes pregnancy fail
lee-boot effect
- females housed in crowded groups have extended estrous cycles by entering a period of pseudopregnancy/extended diestrus
- estrogen dependent pheromone in urine increases prolactin in other mice
coolidge effect
males mated to exhaustion or refusal with one female will recover libido when exposed to anotehr female
the perils of signaling
- many signals are used by predators and parasites as a means of locating prey and hosts
- sexual selection is acting against natural selection
techniques used by wimpy males
- lekking species: have your territory near that of a dominant male and intercept females
- satellite male crickets avoid parasitism by letting signing males attract them
- impersonate dominant male
- wait for dominant males to be fighting/occupied
