EXAM 4 3/27 Flashcards
what is the difference between intersexual selection and intrasexual selection
Intersexual selection involves mate choice.
Intrasexual selection involves competition between individuals of the same sex.
Both forms aim to increase the likelihood of successful reproduction by optimizing specific traits.
primary sexual traits
traits directly related to reproduction, such as fertility and the ability to produce offspring.
secondary sexual traits
traits that may be used as signals to attract mates and do not necessarily contribute directly to survival.
ex: large tails, colorful
what kind of males are females invested in
Females tend to be attracted to males who display exaggerated secondary sexual traits, such as strength, higher status, and physical dominance.
what secondary sexual traits are favored in humans
Larger, stronger males are often seen as more attractive because they are perceived as having better genes and the ability to protect and provide resources. some females may prefer males who display traits of stability and provide resources.
This reflects the balancing act between choosing good genes and ensuring a stable environment for raising offspring.
why do some females prefer males who provide stability and resources over males with
This strategy reduces the risks associated with survival and increases the chances of successful offspring development.
consequences of inbreeding
increase genetic defects and harmful mutations from both parents increases; this is harmful to the populations survival because the defects can accumulate
runaway selection has what kind of feedback loop
This creates a positive feedback loop where the preference for the trait leads to more males exhibiting the trait, and the inheritance of the trait increases its prevalence in the male population.
Do peacocks have larger or smaller tails in captivity?
larger because they dont have evolutionary pressures
female breast size is an example of what
runaway selection, humor and artistic ability
non-visual cues
scent (being more attracted to a male or female when they are fertile) subconscious cue
is it better to be genetically similar or dissimilar
The balance between genetic similarity and dissimilarity is crucial for the maintenance of genetic health and fitness in offspring. Sexual selection is often driven by this balance
cryptic female choice
The ability of females to influence which male’s sperm fertilizes their eggs after mating. allowing females to choose the best genetic material for their offspring, even if they have mated with multiple males.
is cryptic female choice subconscious
Yes. Females may not be actively aware of the influence they have over mate selection.
when is competition most intense in males
in species where males have low reproductive investment like insects. Because the cost of reproduction is relatively low for males, they can afford to mate with multiple females and engage in frequent competition.
what is competition like in females who invest more heavily in reproduction
There may be competition among females to secure high-quality mates. In species where males provide little investment in offspring care, female competition may be more pronounced
sperm competition
Sperm competition occurs when a female mates with multiple males during a reproductive cycle, and the sperm from these males competes to fertilize her eggs. Males may produce larger amounts of sperm to increase their chances of fertilization
what is one strategy employed by sperm to help with sperm competition
Fighter sperm: These sperm are typically slower swimmers and are focused on preventing the sperm of other males from reaching the egg. Males may alter their sperm composition depending on the number of competitors and the timing of copulation. The timing of sperm release, as well as the timing of mating, can affect which male’s sperm successfully fertilizes the egg. (closer to ovulation)
Female Receptivity and Male Sperm Selection
Female receptivity can be influenced by proteins found in male sperm.
These proteins can enter the bloodstream of the female and alter her future receptivity to other males.
This change in receptivity may help increase the likelihood that the female will mate with the same male in the future.
how does sperm interact with the female reproductive tract
Sperm in some species is designed to interact with specific cues within the female reproductive tract.
These cues help guide the sperm to the correct locations for successful fertilization.
By following these cues, the sperm reduces the chances of getting stuck or dying prematurely in the wrong areas.
true monogamy
In monogamous species, males form long-term bonds with females, exclusive reproductive relationships; males typically focus on providing resources, protecting the female, and caring for offspring.
Extra-pair copulation rates are extremely low or almost nonexistent, associated with high levels of oxytocin (females) and vasopressin (males), hormones that reinforce the bond between mates by blocking testosterone receptors and reducing testosterone levels
what is oxytocin known as
the love hormone and it is released during intimate interactions both sexual and non sexual
social monogamy
Individuals may form a pair bond for at least one breeding season.
These species can still exhibit competition, especially after the breeding season ends, when males may try to mate with other females (EPC or cheating does occur). This is what we mean when we refer to monogamy in animal studies.
how do genders inherit predispositions differently
sons for the trait, daughters for the preference. This linkage can persist even if the phenotype skips a generation (offspring are carriers)
what is the potential downside to trait linkage and preference
increase attraction between related offspring, risking inbreeding
Why is breast size a secondary sexual characteristic if breasts produce milk?
breast size does not impact the amount of milk a women can produce
are testes larger in monogamous species or promiscuous species
promiscuous have the largest testes
what is kamikaze sperm
Some species produce sperm types designed to block or attack sperm from other males rather than fertilize; they are slower and stay near the entrance.
what do baculums do
Appears to facilitate copulation. Absence in humans may be linked to erectile dysfunction being a uniquely primate issue for human males
serial monogamy
different breeding partners in different seasons (in humans this is divorce and remarriage)
what kind of monogamy do humans display
weakly socially monogamous
what percentage of men and women cheat
50% of men and 20-30% of women
polygyny
1 male with multiple females; this is very common; males have higher testosterone and lower oxytocin and vasopressin, stronger intrasexual competition, high variance in reproductive success; the top tier male will kill other males so he can reproduce with the females
polyandry
1 female and many males this is very uncommon; males provide more parental care, females may compete and be larger (show dimorphism), female has lower oxytocin and higher testosterone and vasopressin levels, less difference in reproductive success due to egg limits
polygynandry
multiple males and multiple females some social bonds exist, more parental investment than promiscuity
promiscuity
multiple males and females, no bonds, opportunistic mating
scale of sperm size
monogamous/polygynous (small testes) < humans (midground) < promiscuous (ex: bonobos) (larger testes)
