Reports due

Exam 3 take-home available soonDue Th 4/28

Choosing a mate and reproductive strategies are based on methods to succesfully pass on

genes

VolesPrairie

• Monogamous

• Both parents care for young

Montane

• Nonmonogamous

• Mother cares for young briefly

Oxytocin(hormone)

Water/salt balance

Contraction of womb and milk production

Encourages bonding between individuals

Hormones are molecules produced in one cell and signal another.

Oxytocin(hormone)

Water/salt balance

Contraction of womb and milk production

Encourages bonding between individuals

VolesPrairie

• Monogamous

• Both parents care for young

Montane

• Nonmonogamous

• Mother cares for young briefly

VolesPrairie

• Monogamous

• Both parents care for young

Montane

• Nonmonogamous

• Mother cares for young briefly

Same levels of oxytocin

Hormones are molecules produced in one cell and signal another.

VolesPrairie

• Monogamous

• Both parents care for young

• More receptors

Montane

• Nonmonogamous

• Mother cares for young briefly

• Less receptorsSame levels of oxytocin

VolesPrairie

• Monogamous

• Both parents care for young

• More receptors

• ?

Montane

• Nonmonogamous

• Mother cares for young briefly

• Less receptors

• ?

Same levels of oxytocin

Inject hormone into brain

VolesPrairie

• Monogamous

• Both parents care for young

• More receptors

• Monogamous

Montane

• Nonmonogamous

• Mother cares for young briefly

• Less receptors

• Nonmonogamous

Same levels of oxytocin

Inject hormone into brain

VolesPrairie

• Monogamous• Both parents care

for young

• More oxytocin receptors

• ?

Montane• Nonmonogamous• Mother cares for

young briefly

• Less oxytocin receptors

• ?

Same levels of oxytocin

Block receptors

VolesPrairie

• Monogamous• Both parents care

for young

• More oxytocin receptors

• Nonmonogamous

Montane• Nonmonogamous• Mother cares for

young briefly

• Less oxytocin receptors

• Nonmonogamous

Same levels of oxytocin

Block receptors

VolesPrairie

• Monogamous• Both parents care

for young

• More oxytocin receptors

• Monogamous

Montane• Nonmonogamous• Mother cares for

young briefly

• Less oxytocin receptors

• Monogamous

Same levels of oxytocin

Increase levels of receptors (genetically) in ventral pallidum

VolesPrairie

• Monogamous

• Both parents care for young

• More receptors

Montane

• Nonmonogamous

• Mother cares for young briefly

• Less receptorsSame levels of oxytocin

Sexual Dimorphism

Human Females:~1 egg/month

Human Males:250,000,000 sperm/ ejaculation

Fig 46.12

I hope Pat likes my feathers because I am tired of dragging them

around everywhere.

Fig 23.15

1

2

Which is male?

1

2

Which is male?

Sexual Dimporphism: morphological differences between males and females

Sexual Dimorphism

Male barn swallows have longer tails than females

Why do males have long tails?From “Biological Science” 3rd ed. by Scott Freeman -fig 51.5

Why do males have long tails?

From “Biological Science” 3rd ed. by Scott Freeman -fig 51.5

feathers cut and reattached

captured and released

Female grizzly bears cannot reproduce while lactating. Therefore they can only

reproduce every once every 3 years…

…this leads to competition between males

Male elephant seals compete for access to females in limited beach territories. They are on average 4 times bigger than females.Male elephant seals weigh ~3 tons.

From “Biological Science” 3rd ed. by Scott Freeman -fig 25.14

Competition between males is fierce, only

a few males father most of the offspring.

90% of males never successfully reproduce

60% of females do not successfully reproduce

From “Biological Science” 3rd ed. by Scott Freeman -fig 25.14

Average height/weight by sex in U.S.

Ratio of Weight Male/Female

M/F

Primates have different reproductive stratagies

Testes Compared to Overall WeightTesticle size (oz) per body w

eight (lbs)

Our closest living relative...bonobos

http://www.youtube.com/watch?v=eubDSQrFako Stop at 1:53

http://www.ted.com/talks/lang/eng/isabel_behncke_evolution_s_gift_of_play_from_bonobo_apes_to_humans.html