Exams back
W 2/18
Bonuses
Do Males and Females have different
attitudes toward sex and relationships?
Screw worm
flies
F
M
sterile
Sterile male screw worm
flies led to decreased
populations because of
screw worm monogamy.
F
M
sterile
In most other species,
because females mate
with multiple males,
introduction of sterile
males has little effect.
Sterile male screw worm
flies led to decreased
populations because of
screw worm monogamy.
F
M
sterile
In most other species,
because females mate
with multiple males,
introduction of sterile
males has little effect.
Hi, want to study
biology together?
M
F
fertile
F
M
sterile
These birds are nesting together, they must be
an “item”
10-40% of offspring in “monogamous” bird
species are fathered by an extra-pair male
•Social Monogamy = pair lives/works together,
but not “faithful”
•Sexual Monogamy = pair raise young and
only copulate with each other
Mating pairs share genetic information and possibly
help in child-rearing
In mammals, child-rearing is most commonly
done by the female. She provides milk.
Less than 0.01% of mammals are monogamous
Do Males and Females have different
attitudes toward sex and relationships?
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out
…Would you go out
with me tonight?
with me tonight?
= 50% yes
= 50% yes
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out with …Would you go out with
me tonight?
me tonight?
= 50% yes
= 50% yes
…Would you come to
…Would you come to
my apartment
my apartment
tonight?
tonight?
= 6% yes
= 69% yes
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out with …Would you go out with
me tonight?
me tonight?
= 50% yes
= 50% yes
…Would you come to
…Would you come to
my apartment tonight?
my apartment tonight?
= 6% yes
= 69% yes
…Would you go to bed …Would you go to bed
with me tonight?
with me tonight?
= 0% yes
= 75% yes
Why do Males and Females have
different attitudes toward sex and
relationships?
The male
perspective on
monogamy
Eggs require
large resource
input.
A clutch of bird
eggs can be ~20%
of bird’s weight.
Sperm are
cheap.
The female reproductive system
Sperm can survive for several days in a
woman’s reproductive tract.
Sperm competition:
Sperm can survive for several days in a
woman’s reproductive tract.
In Great Britain in a survey of 4,000
women…
0.5% had sex with 2 different men within
30 minutes…
30% within 24 hours
= sperm competition.
The female reproductive system
Female mammals
provide additional
resources in form of
milk.
What are the consequences of the different
male and female attitudes toward sex and
relationships?
Zebra Finch
Zebra finch pairs were allowed to mate ~9 times
Then a new male was brought in and allowed to
mate with the female once.
Last male advantage
The last male that only mated
once fathered 54% of offspring
Original male (mated 9 times)
fathered 46% of offspring
Last male advantage
To ensure fatherhood males mate guard and produce copious
quantities of sperm
Fig 48.4
Why does the 2nd male have an
advantage?
Fig 48.4
Why does the 2nd male have an
advantage?
Why might females choose to mate with
multiple males?
Gunnison’s Prairie Dogs
Sexually
monogamous
female squirrels
have a 92% chance
of successfully
giving birth.
Gunnison’s Prairie Dogs
Sexually
monogamous
female squirrels
have a 92% chance
of successfully
giving birth.
Non-monogamous
females have a
100% chance of
giving birth
Mating pairs may be genetically incompatible
Cystic Fibrosis: F= normal, f= cystic fibrosis
Mom=Ff
Dad=Ff
F
F
f
FF
Ff
Versus
Mom=Ff
f
Ff
ff
Dad=FF
F
f
F
FF
Ff
F
FF
Ff
Can females detect compatible genes?
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
How can a female know which male
has successful genes?
Females may choose traits, like large
displays, that are disadvantageous for
male survival.
How can females determine “good” males?
Color:
Bright coloring can be correlated with health…
But a male
with a
mate is
judged as
being high
quality
even if he
is less
colorful
Purple Martins
After successfully
mating, male purple
martins call and
attract younger males
The older males then
cuckold the younger
male’s females
Younger males with
nests near older males
only father 29% of
eggs in their nests.
Older males produce
4.1 offspring with
their mate and 3.6 by
younger neighbor’s
mate.
Younger males with
nests near older males
only father 29% of
eggs in their nests.
Females use
several factors to
select a mate.
Reproductive success = Evolutionary success
Reproductive success = Evolutionary success
www.jayhosler.com
Choosing a mate and reproductive strategies
are based on methods to succesfully pass on
genes
Exams back
W 2/18
Bonuses