Lab 3 - The Mating Game (sexual selection)

objective of activity

3 exercises simulate selective pressures on males and females that influence sexual behavior

sexual selection

special case of NS acts on org’s ability to obtain/successfully copulate w mate

• selects for animals that go to extreme lengths for sex

extreme lengths examples

peacocks elaborate tails

elephant seals fight over territories

fruit flies dances

deliver persuasive gifts

inTER sexual selection

sexually selected trait designed to attract opposite sex

inTRA sexual selection

sexually selected trait designed to repel rivals of same sex

sexual selection can be powerful enough to

produce features that are harmful to individual’s survival

True or False: There are inherent biological asymmetries between the sexes

TRUE

Inherent biological asymmetry: MALES

produce many small, cheap gametes (sperm)

provide little to no care for offspring

Inherent biological asymmetry: FEMALES

produce fewer, larger, expensive gametes (eggs)

typically provide parental care

Females usually have a ____ potential reproductive rate

LOWER

adult sex ratio

proportion of males to females in a population that has reached reproductive age

operational sex ratio

ratio sexually competing males ready to mate to sexually competing females ready to mate

male biased operational sex ratio

more males than females available to mate at any given time

results of male biased OSR

males tend to compete for sexually receptive females

females can choose among males

“sex role reversal”

males provide more parental care

females compete for males

males become choosier sex

Each student assigned

sex

identification number

quality score

Sex designations

prelab: blue/pink headbands

lab: green/yellow sashes

quality designations

prelab: number of spots

lab: number of spots on sashes 1-5

Exercise 1

typical mating dynamic

F takes pair of gametes to instructor

M stay in mating pool donate gametes

reproductive success points

identities M + F, sum point values of gametes → reprod success of offspring

Exercise 2

anthro-simulated mating dynamic

both parents carry pair of gametes to instructor

simulates human reproductive behavior

Exercise 3

choose your own adventure mating

results

lower quality - lower reprod success (should be)

Lettering M/F

Females: A-I

Males: R-Z