3. Mating and Reproduction

What did the casual sex study find?

• men more likely to agree

• women are not

• this is due to differences in energetic investment in reproduction

How is energetic investment in reproduction typically larger for females?

1. larger gametes

   • egg larger than sperm

2. internal gestation

   • carrying a fetus to term

3. lactation

   • in mammals

true or false: the energetic investment in reproduction differences between the sexes, but the pay off is the same

true, you get an offspring

• sane payout, less investment, men def want yo do it

How does access to additional mates change fitness for males vs female?

• more access increases fitness for males

• more access does not fitness for females

• Natural selection selects accordingly

What are the two bid sex behavior predictions when it comes to mating?

1. sex that invests more will be more discriminating

2. Sex that invests less will compete amongst themselves for access to the high-investing sex (will seek greater paternal certainty

What is the more discriminating sex looking for?

• honest signals of health

  • how many eyespots peacock produces

• value fighting ability

• a commitment to invest

  • courtship dance'

  • nuptial gifts

What is the sex that invests less in competition for? What is the driver for this competition?

• competition for access

• mate guarding/ extended mating

• sperm competition / anti-sperm

  • cuckoldry is common,

Male to male competition for these things is spurred by paternal uncertainty.

What is polygamy? Describe the variaitons in reproductive success for each sex.

• A mating system with:

• high variation in male reproductive success

• low variation in female species

• majority of mammal species

• one male mates with multiple females

What is polyandry? Describe the variation in reproductive success for each sex.

• A mating system with:

• low variance in male reproductive success

• high variance in female reproductive success

• one female bonds with multiple mates

What is monogamy? Describe the variation in reproductive success from each sex.

• mating system with

• low variance of reproductive success for either sex

• low number of mates for each

• one male mates with one female

What is sexual dimorphisms? What leads to more radical sexual dimorphisms?

• the difference in size and physical characteristic between sexes

• the more asymmetric the investment, the more radical the sexual dimorphisms

• when investment is more equal, the two sexes look more similar

  • sexual monomorphism

What are the defining features of a mammal?

• fur

• lactation

Why do gorillas have smaller testes than chimps?

• In gorillas most of the females mate with the same male

  • more paternal certainty

• In chimps, the females mate with many males

  • need to produce more sperm to increase paternal certainty

  • 16x larger

Whay do we see more monogamy among birds then mammasl?

• gestation can be done by both in birds

• and both can food and care for them

• the male spend lots of time caring for their offspring more than other species at least

  • hence they don’t have time to be mating elsewhere