evol sex gender 2

Sexual reproduction

the production of new living organisms by combining genetic information from 2 different individuals of different types (sexes)

The paradox of evolution

asexual reproduction is simpler, so why do we reproduce sexually

two-fold cost of sex

a disadvantage of sexual reproduction

sexual females can produce twice as many childbearing offspring (females) as sexual females due to the time and energy of finding mates

reduced relatedness

a disadvantage of sexual reproduction

Sexually reproducing organisms pass only half of their alleles/genomes to their offspring, because meiosis generates gametes that are haploid. This halves the relatedness between parents and their progeny.

disease

a disadvantage of sexual reproduction

diseases have a higher chance of being passed through generations since the same genes belong to each organism

novelty

an advantage of sexual reproduction

Recombination increases the rate of adaptive evolution
of a species, reducing the risk of extinction due to meiosis

mechanism to lose harmful mutations

an advantage of sexual reproduction

due to recombination, sexual reproduction avoids Muller's ratchet

enhanced adaptation due to directional selection

Faster to mutate into a perfect genetic sequence; Sex reproduction and recombination provides a way for us to "keep up" with evolving pathogen populations and environments that put us under directional selection.

Muller's ratchet

Irreversible accumulation of mutations in asexual organism's - may be why so many asexual species go extinct

rotifers

tiny "ancient" asexual animals that inhabit fresh water, the ocean, and damp soil

When environmental conditions changed, this animal switched to reproducing sexually to adapt;

in populations in homogenous environments, rate of sex was none

Higher rates of sex in changing environments

Isogamy

reproducing using similar gametes

Anisogamy

reproducing using different gametes; in gametes pair one is small and the other is big and less mobile

Females

type of sex

produce larger but fewer eggs (ova); produce large gamete; is diploid; also XX; also determined by temp

Males

type of sex

produce smaller and mobile reproductive cells (sperm); produce small gamete; is haploid; also XY; also determined by temp

SRY

sex determining feature of the Y chromosomes; when turned on and expressed, it expresses the Y chromosome; is NOT required for determining males

the gene on the Y chromosome whose product instructs the undifferentiated fetal gonads to develop into testes

Combination

sex reversal due to environment
Provides a precedent for environmental over-ride of genetic sex determination

Australian lizards

animal example of sex combination; sex change caused by hot temps

echiurans (marine spoon worms)

Animal example of absence/presence of one sex determining sex

Some species have "dwarf" male
Sex is determined via contact with the proboscis of an adult female, the organism becomes male; if no contact, female

Hermaphrodism

existance of reproductive organs of both sexes in the same individual; organism doesn't fit into a gamete binary

Simultaneous Hermaphrodism

can always produce either gamete types whenever

Hamlets and Chalk Bass

Example of Simultaneous Hermaphrodism

Form long term monogomous relationships
Fish take turns alternating between laying eggs and producing sperm

dynamic sex determination

male and female criscrossing

Okinawan Goby

example of dynamic sex determination

Can switch between being male or female for life; can continuously switch; not liked into gender

Live in monogamous pairs

Initially 80% females and 20% males at birth, but change sex based on who they run into

Lizard Island Goby

example of dynamic sex determination

All mature into females

Some later become males; some males change back to females later

Ambiguous bc all males contain early-stage oocytes in their gonads

Tropical ginger

example of dynamic sex determination

Male in the morning, then switch sexes in afternoon

Sequential Hermaphrodism

sometimes produce eggs, sometimes sperm, so changes sex over time; requires dynamic sex determination

Lots of fish, some jellyfish, some gastropods

Gonochrosim

animals with separate sexes, male and female

Androdioecious

includes males and other sexes

hermaphrodites plus males

hermaphrodites plus males plus females

parthenogenesis

parthenogenesis

Asexual reproduction in which females produce offspring from unfertilized eggs.

Pseudohermaphrodites

individual of one sex has external genitalia superficially resembling those of a different sex

Hyenas

example of pseudohermaphrodites

Has a "psuedo-penis" that is actually a clitoris; birth canal runs through clit rather than forming a seperate vagina

Intersex

having gonads to make eggs and sperm and/or sperm-related and egg-related plumping parts

possessing biological sexual characteristics of both sexes

Typically infertile

Vanuatu pigs

example of intersex

7 named genders

Male gonads w intermediate forms of feminized external genitalia

Mixed reports of behavior

Some are infertile, but birth frequency is high

Old world moles

example of intersex

Intersex gonads

Females have ovotestis

Produce no sperm, but have hormones

Possibly on way to becoming Pseudohermaphrodites

Gender in Humans

the way a person expresses sexual identity in a cultural context

Gender Broader

the appearance of behavior and life-history of a sexed-body

Marina amphipods

have more than 2 sexes

Alphas - have a den and mate w females

Betas - trick alphas into thinking they're female, get into den, mate and steal female

Gammas - so small, males don't notice them, sneak in and out to mate with females

Side-blotched lizards

have more than 2 sexes

Males w diff colors exhibit different behaviors

Orange - chase away males to mate w females

Blue - go in pairs; one mates and the other protects from other males

Yellow - appear female to avoid confrontation w orange male and sneak w actual female

Marina amphipods beta

sex of Marina amphipods

trick alphas into thinking they're female, get into den, mate and steal female

Marina amphipods gamma

sex of Marina amphipods
so small, males don't notice them, sneak in and out to mate with females

Marina amphipods alpha

sex of Marina amphipods

have a den and mate w females

White-throated sparrows

have more than 2 sexes

High contrast males - aggressive, territorial,
High contrast females - aggressive, territorial,
Low contrast males - passive, but better w offspring
Low contrast females - passive, but better w offspring

opposites attract \-- offspring do better when one parent is high contrast and other is low contrast

Transgender in animals

individuals who produce gametes of one sex and yet behave as the other sex

Beta amphipods

Transgender in animals

trick alphas into thinking they're female, get into den, mate and steal female

Yellow-throated side-blotched lizards

Transgender in animals

appear female to avoid confrontation w orange male and sneak w actual female

Androchromotypics

Females that produce eggs but have coloration and behavior of males; left alone by males during mating season to survive

Dragonflies/damselflies

example of Androchromotypics/is transgender

Females that produce eggs but have coloration and behavior of males; left alone by males during mating season to survive

Lioness of Botswana

example of Androchromotypics/is transgender

Have manes and roar
Inside family group, treated as females
Outside family group, treated as males

Dimorphism

when males and females look or act differently, including sexually

Sexual Selection

form of natural selection that occurs when individuals differ in their ability to compete with others for a mate or attract members of the opposite sex

Intrasexual selection

individuals of one sex compete among themselves for access to the other sex

deer

example of Intrasexual selection

Ritualized battles using antlers determine dominance → correlates w number of matings

elephant seal

example of Intrasexual selection

seal that fights for dominance

Topi antelope

example of Intrasexual selection

females fight for access to male

Sperm competition

Intrasexual selection after mating

determines whose sperm will fertilize

Sperm scoops (males)

example of sperm competition

scoops out sperm from other males to replace sperm

Dilution effect (males)

example of sperm competition

producing more sperm; testis size/sperm load

Copulatory plug

example of sperm competition

males prevent females from mating for amount of time, giving sperm time to fertilize

Mate guarding

males/females attempt to prevent other males/females from gaining access to a potential or actual mate

Female beetles to males
Male mice to females

Intersexual selection

members of one sex choose certain mates of other sex

Indirect selection

picking criteria that will indirectly give female fitness benefits; superficial qualities; male is not involved with offspring

Healthy mate

preference in indirect selection

wants healthy offspring

Good genes

preference in indirect selection

colorful feathers, best dance \= best/healthy genes

Ex. red underbelly of fish means that there is higher resistance to infection/tapeworm

Sexy sons (runaway selection)

preference in indirect selection

female chooses most attract male to mate with so future sons are most attractive for a mate

Sperm management

step in intrasexual selection, is switch from intersexual selection

allows females to choose which sperm they want in their body

Spotted sandpipers

Cryptic female choice

step in intrasexual selection, is switch from intersexual selection

Females choose which sperm to use

Females sometimes regulate size, chemical composition, or sex of eggs

Dependent on the perceived quality of the mate or environmental conditions

Indiscriminate sex (often male)

Large size, aggression, weaponry, increased sperm & sperm delivery, behavior or morphology to remove other sperm, or prevent a partner from mating again

Can and will choose anyone

Choosy sex (often female)

Mechanisms to avoid mating with subordinate or smaller males (or using their sperm), mechanisms to judge best males

Picks one mate specifically

Operational Sex Ratio

the ratio of sexually receptive males to receptive females at one time; result of choosy vs indiscriminate

No bias in operational Sex Ratio

1:1
For one female they choose one male

Bias in operational Sex Ratio

2:1 or 5:1, etc.

For two females they choose one male, etc.

One sex (often females) should be "choosier" sex and should maximize the chances that their offspring will survive to reproduce, and be successful in dinging mates and be as diverse as possible

Monogamy

one male, one female; one male mates with one female in a breeding season

Social monogamy

male and a female bond and stay together to help rear offspring

Sexual/genetic monogamy

type of mating system

male and female of the pair are always the parent and so are the offspring they raise

cost of Sexual/genetic monogamy to males

cost of \________ (sexual system)

Lack of diverse offspring
Fewer mates → Low number of offspring

cost of Sexual/genetic monogamy to females

cost of \________ (sexual system)

Lack of diverse offspring
Low number of offspring
Lack of options

benefits of Sexual/genetic monogamy to males

benefit of \________ (sexual system)

Does not require much energy → guaranteed mate
Paternity assurance
Mate guarding → prevents females from mating with others

benefits of Sexual/genetic monogamy to females

benefit of \________ (sexual system)

Guaranteed mate
Increased survivorship of offspring

Mate assistance
females would be unable to raise offspring by themselves
Pregnant female survivorship increases

Mate assurance

Birds

Example of monogomy

But EPCs are common (Extra-pair copulations)

Usually both males and females participate in EPCs\

Females EPCs are very costly to males (help rear another males offspring)

Polygyny

type of mating system

one male, many females

Costs of polygyny to males

cost of \________ (sexual system)

Lots of energy to keep harem → need to defend
If not on top, males never get to reproduce → probability of mating is low

Costs of polygyny to females

cost of \________ (sexual system)

Less diversity
Competition among females to access males for resources → need to share resources with other females

benefits of polygyny to males

benefits of \________ (sexual system)

Top males can have really high fitness
Have genetically diverse children
Large numbers of offspring*

benefits of polygyny to females

benefits of \________ (sexual system)

Have genetically diverse children
Guaranteed offspring
Just increased quality of offspring*

Female defense polygyny

type of polygyny mating system

Groups form for anti-predation, hunting/foraging, defense, etc. → one male "takes" the group and defends group from other male competitors to monopolize the mates
If females range is small relative to male, then the male will be polygynous

Resource defense polygyny

type of polygyny mating system

males defend territories with key resources for females

Ex. females will mate with males that have better territory, can lead to multiple females w one male if sharing doesn't result in lower breeding potentional

Scramble competition polygyny

type of polygyny mating system

females and resources are widely dispersed

Males attempt to find scarce females quickly

Ex. thirteen-lines ground squirrels, garter snakes from video

Lek polygyny

type of polygyny mating system

males defend display area like sage grouse; only a space for attracting a mate, nothing else

Resources cannot be monopolized

Polyandry

one female, many males

cost of polyandry to males

cost of \________ (sexual system)

Fewer mates/low paternity

cost of polyandry to females

cost of \________ (sexual system)

Costs of maintaining top spot, some females dont mate

benefit of polyandry to males

benefit of \________ (sexual system)

Some chance of paternity
Higher survivorship of offspring

benefit of polyandry to females

benefit of \________ (sexual system)

Increased diversity of offspring
Increased paternal input

Polygynandry

both males and females have multiple partners; promiscuity

Red queen effect

for a species to survive male and females must continuously change just to stay where it is evolutionarily

or coevolving populations, to maintain relative fitness, each population must constantly adapt to the other; this term was borrowed from Lewis Carroll's Through the Looking-Glass by Leigh Van Valen to refer to biological arms races, such as those between parasites and their hosts

Drosophila species

Example of Red Queen Effect

Males produce toxins in semen to compete with other males

Toxins shorten the lifespan of females
Females respond by producing counteractive proteins
Males produce more toxins


Experiment:
Force monogamy for 30 generations → both stopped producing "costly" toxins/counter-toxins

Geladas monkeys

Example of Red Queen Effect

Females choose the males, but males control the harem once chosen
Males provide them with protection
But females have ultimate control since they choose males
Female is red queen

Hamadryas Baboons

Example of Red Queen Effect

Men control the females; "punish" females if they get too close to males
Reinforcing my hate for men hahahahhahahahhahahaha
Male is red queen

Pied Flycatcher bird

Example of Red Queen Effect

Female chooses the male
Male guards female
Male has multiple separate females but the male can only provide for one nest, so other families struggle
Male has high fitness but "mistress" has lower fitness since some of her chicks died
Male is red queen

Jacanda bird

Example of Red Queen Effect

Female defends territory and mates w 3 or 4 males
Females fight for males and smash each others eggs to mate with males
Males take care of kids
Female is red queen