because eggs are bigger than s.p.e.r.m.

sexual selection is…

non-random, designed to increase mating success, can improve survival but does not have to, and creates sexual dimorphism.

sexual dimorphism

differences in physical characteristics between males and females of the same species.

interaexual selection

a direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.

intersexual selection

active choice of one sex for mates, often females choice.

Bateman’s principle

the sex with the greatest variation among individuals in reproductive success will be subject to stronger sexual selection

egg vs. sperm

eggs are larger investments, resulting in fewer produced, while sperm are smaller investments, leading to higher production

… provides more parental control

females

the Pharaoh Concept

males will kill the offspring of other males/castrate other males to ensure the success of only his offspring

female limitations

limited in how many offspring the can produce

male limitations

limited by the mating they can achieve

this sex is choosey

females

this sex is competitive

males

sexy sons

females with a preference for a particular trait produce sons with that trait

sensory exploitation

a theory of sexual selection that posits that females may initially prefer male traits that elicit the greatest amount of stimulation from their sensory systems.

good genes hypothesis

the hypothesis that na individual chooses a mate that possesses a superior genotype

direct benefits

benefits that affect a particular female directly, such as food, nest sites, or protection

types of mating competition

pre-mating, post-mating, post conception

pre-mating

physical combat, threats of combat, posturing, dominance hierarchies, territoriality

post-mating

interference with subsequent matings by other males, mate guarding, sperm competition

post-conception

return females to breeding condition sooner, infanticide

signal honesty

Reliability of signals as indicators.

runaway traits

traits passed down because of female choice

sex-role reversal

a change in the typical behavior patterns of males and females, as when, for example, females compete for access to males or when males choose selectively among potential mates

true communication

both sender and receiver benefit

Manipulation and Deceit

sender benefits, receiver unaffected or harmed

handicap principle

theory of sexual selection that argues only the fittest individuals can afford costly traits

who came up with the handicap principle?

Zahavi and Zahavi

costly signals are...

more likely to be honest

bower birds use...

sensory exploitation

semelparity (suicidal reproduction)

Reproduction in which an organism produces all of its offspring in a single event; also known as big-bang reproduction.

examples of organisms who engage in semelparity

salmon, many insects and spiders (austrailian redback spider)

why do organisms partake in suicidal reproduction?

short mating season, synchronized mating, low probability of subsequent matings

long sperm is...

expensive and limiting

long sperm is an example of...

runaway selection

sequential hermaphrodism

individuals change sex during lifetime either male or female

protandry

Born a male, change to a female

protogyny

Born a female, change to a male

facultative

organism that can survive with or without oxygen

size-advantage model

If an individual of a certain sex could significantly increase its reproductive success after reaching a certain size, it would be to their advantage to switch to that sex