sex cluster fall quiz 1

schema

mental structures in our mind that organize, categorize, and

interpret pieces of information and how they are related

gender schemas

mental structures in our mind that organize,

categorize, and interpret pieces of information and how they are related

Once formed, hard to change

• Discount contrary evidence – ignore information that

contradicts our existing schema

gender identity

An individual’s deeply felt, internal psychological sense of being a man, a

woman, a blend of both, or another gender (e.g., non-binary, agender

masculinity-feminity

How a person’s psychological characteristics and behavioral tendencies align with

societal norms and stereotypes associated with male vs. female-typical behavior

gender expression

External presentation and public display of gender through visible choices such as

clothing, hairstyle, makeup, body language, mannerism, social behavior.

hormones

organic chemical messengers produced and

released by endocrine glands

• released into bloodstream (but not always)

• act on target tissues (with receptors)

• Hormones coordinate physiology and behavior

by regulating, integrating, and controlling bodily

function

• Hormones change gene expression & cellular

function

phenotype

physical characteristics or behavorial

the set of observable characteristics of an

individual resulting from the interaction of its genotype

with the environment

sex determination

determination of

the type of gonads: i.e. testes vs. ovaries

xx vs xy

sexual differentiation

developmental process by which non-gonadal

tissues are differentiated in the two sexes

sry

Sry induces testis formation directly

in Males

ene encodes a protein that initiates a

cascade that induces differentiation of Sertoli

cells, the first testicular cells!!

• Ovary develops in absence of Sry, no matter

what the sex chromosome complemen

mullerian ducts

become oviduct, uterus,

upper vagina

wolffian ducts

become efferent ducts, ductus

deferens/epididymis (seminal duct) and associated

glands

Sertoli cells secrete Müllerian Inhibiting Hormone,

causes involution of female ducts (oviducts, uterus,

upper vagina)

• Leydig cells secrete testosterone which causes

survival of the wolffian ducts and masculine

differentiation (penis, scrotum, sperm ducts, brain)

• Females lack Sertoli cells, so they do not make MIH

and their Mullerian ducts survive. Females also

lack Leydig cells (testosterone) so their Wolffian

ducts w/o androgens involute.

• These hormone effects are permanent and

irreversible

testosterone

defeminizes sex behavior/masculinizes it

absence allows for feminine development

testes secrete to masculinize brain

gynadromorph

Behavior completely

masculine:

song

courtship

copulation

Left ovary and right testis:

Genetic sex differs on right and left side of body (gonadal hormones act on both sides)

ZZ (male) and ZW (fem) genes act on one side

half-half finch

x chromosome

described by:

n humans, all cells in females are XX; all cells in

males are XY

But, in females, one X is “inactivated”, so # of X

genes are roughly “equivalent” in male and female

cells.

But, females get one X from mom and one X from

Dad; males get their X from mom.

Female cells “inactivate” either genes on Mom’s or

Dad’s X.

Cells in females can be a “mosaic” of X genes

from Mom or Dad.n humans, all cells in females are XX; all cells in

males are XY

But, in females, one X is “inactivated”, so # of X

genes are roughly “equivalent” in male and female

cells.

But, females get one X from mom and one X from

Dad; males get their X from mom.

Female cells “inactivate” either genes on Mom’s or

Dad’s X.

Cells in females can be a “mosaic” of X genes

from Mom or Dad.

parthenogenesis

reproduction from an ovum without

fertilization

N. Mexico Whiptail

Lizard

Lizards in the

Aspidoscelis genus,

like this New Mexico

Whiptail (Aspidoscelis

neomexicana),

reproduce asexually.

All of these lizards are

female.

cost of sex

time, energy

Can’t forage, evade predators during mating

Sexual reproduction slower than asexual

reproduction

Risk of sexually transmitted diseases,

parasites

BREAKING UP FAVORABLE MUTATIONS

grandchildren asymmetry/cost of males

A sexually reproducing female has to make two

offspring to replace herself.

An asexual female produces two of herself

each generation

Asexual female will always outcompete a a

sexually reproducing female

paradox of sex

if it is so costly, why is it so

common?

muller’s ratchet

an evolutionary genetics process where asexual populations accumulate harmful (deleterious) mutations in an irreversible manner

kondrashov’s hatchet

Harmful mutations can interact in a compounding way. Having a few mutations might cause minor fitness loss, but crossing a specific damage threshold causes a steep, dramatic drop in fitness or survival

Individuals that fall past the damage threshold are heavily selected against or eliminated. Because sex groups multiple bad mutations into fewer individuals (like a "hatchet" cutting them out all at once), the population clears out harmful mutations faster than asexual populations.

lottery model

Sexual reproduction increases variance in

offspring, which would be useful in a

changing environment

red queen

Parasites cause an evolutionary arms race

• Parasites become adapted to asexual

species

• Sexually reproducing species constantly

change as a result of recombination, so

better able to escape parasite dominance

new zealand snail evidence

anisogamy

Gamete size defines the difference

Trade-offs in gamete size

• Small gametes cheaper to produce

• Large gametes more expensive, but

produce zygotes with higher survival

• Given costs, strategy can be produce

many small gametes or few large ones

• Survival/size relationship non-linear

sexual selection arises:

Males produce more sperm than females

produce eggs

• Number of females is not expected to

greatly exceed number of males (Fisher

condition)

• Many sperm will fail to locate eggs,

whereas most eggs will be fertilized

female choosier, male compete

hermaphroditism

Escapes cost of males problem

• Useful strategy when encountering mates is

rare

flatworms

what is sex?

1) Who you are - gamete size

2) Who you can mate with - gamete size and/or

mate type and other isolating mechanisms

3) Who are your parents - parental number

shows least variation

parental investment

PI = care that increases the success of current

offspring at the cost to the parents ability to

invest in future offspring

• Sex with higher PI -> longer to complete a

breeding event and reenter the breeding pool

• Time out period

• Differences in time-out result in asymmetry in

availability of mates

• Sex with greater PI will be limiting sex, other

will compete for mates

operational sex ratio!!!

mate choice

generates sexual competition

• Does not mean that competition in one sex

means the other is being choosy

Males: if PI is low, gain little by rejecting any females,

maximize mating rate

Females: if PI is high, then prolonged time out, more

to gain with each individual mating, regardless of

mating rate

strategy

behavioral mechanisms that

produce particular course of behavior in

particular contexts

Does not imply conscious reasoning,

deliberate planning, or intent

Benefits & costs = effects on fitness

• All other things being equal, traits that

enhance efficiency, skill, etc. will also

enhance fitness

male = energy to finding mates

female = finding resources

sexual selection

a process which

acts on traits that affect differential

reproduction among individuals of

the same sex and species.

Females: resources

• Males: access to females

A male can mate with as many

females possible, suffer little

reductions in fitness if he mates with

a poor quality female

A female suffers great costs of time

and energy by mating with a poor

quality male

intersexual selection

female choice

Behavioral pattern in one sex which increases

the probability of fertile matings with certain

members of the opposite sex

Usually “choosy females”

Females have more to loose by investing in

poor male mates

intrasexual competition

Usually Male-male

Results in differential reproductive success

which provides the force of natural selection

Often occurs when males can monopolize

resources in some manner

sexual dimorphism

Should be greatest in species that can

monopolize many mates

Harem breeders = most dimorphism

Monogamous = least dimorphism

sperm competition

competition within a

single female between the sperm from two or

more males for the fertilization of an ova

• Male-male competition in the post-

copulatory arena

raffle principle

if sperm competition unavoidable (sperm

compete for access to ova):

Greater sperm number enhances reproductive

success

testis size: Greater testis relative mass in species

with multi-male multi-female breeding

Species with monogamous mating tend

to have smaller relative testis size

intersexual coercion

Use of force or threat of force

Functions to increase female will mate with

male at time she is fertile

Decreases chance female will mate with other

males

infanticide

infanticide

killing of an infant sired by

another male

Well documented male strategy in many male

primates

Typically occurs with changes in male status

Reduces IBI in females, giving immediate mating

opportunities to males - enhances male fitness

counterstrategies:

Mother, other adult females, and adult males

defend victims of attack

Fathers and males present at conception

defended infants

Males who were not present at conception

never defended infants

paternity confusion

anti-infanticide strategy

Have extended periods of sexual

receptivity

• Mate with multiple males

• “Pseudestrus” (mating during

pregnancy or when infertile for other

reasons)

• Concealed ovulation

mating patterns

1 - Opportunistic - noncompetitive mating, when

receptive female may be mated by all community

males

2 - Possessiveness - when a male establishes special

short-term relationship with receptive female, may

prevent lower-ranking males from copulating

3 - Consortships - when a single adult male escorts

a female away from community males and maintains

exclusive access, both taking steps to avoid others