envs lecture 10 Flashcards
sexual reproduction
two individuals fertilize each others sex cells and the process creates opportunities for genetic recombination to occur via meiosis
what does process of sexual reproduction do
creates opportunities for genetic recombination to occur via meiosis
what do some animals have besides sexual reproduction
internal fertilization
what else can some animals do besides sexual reproduction and internal fertilization
vectors
examples of vectors
wind, water (broadcast spawning), other animals
what do bacteria and fungi do
parasexuality/parasexual reproduction
what do bacteria and fungi have (w/r to recombination)
recombination in mitosis instead of meiosis
what is parasexuality
bacteria pass DNA b/w each other via conjugation
what is conjugation
involves transfer of plasmids, which sometimes carry genes for antibiotic resistance
how else can parasexuality occur (besides conjugation)
other bacteria are able to absorb naked DNA left in environment
basically what is conjugation
horizontal gene transfer; DNA transferred from donor to recipient bacterium via direct contact (or bridge-like connection), cell-cell contact
how do viruses reproduce
similarly; several viral particles infect the same host, progeny that are produced carry a mix of their genotypes
describe mating in frogs and toads
sexual reproduction –> recombination occurs via meiosis
describe reproduction in bacteria
parasexual reproduction –> thru conjugation
hermaphrodites
each individual has both male and female gonads
how do hermaphrodites mate
some mate w/ other individuals, others self fertilize
examples of hermaphroditic organisms that mate
earthworms, snails, slugs
example of hermaphroditic organisms that self-fertilize
plants
what is hermaphroditism a form of
reproductive assurance
reproductive assurance (hermaphroditism)
increases chances of reproduction when potential mates are scarce
what are clownfish
sequential hermaphrodites
describe how clownfish are sequential hermaphrodites
first male, then later changes to females
what is key difference b/w males and females
gametes come in two sizes
anisogamy
dimorphism in gamete size (males and females having two diff gamete sizes)
describe egg
large, immobile, provisioned
describe sperm
small, mobile, not well provisioned
what does well provisioned mean
inhibiting movement
when do gametes have high fitness
if large, well provisioned (inhibiting movement)
when else do gametes have high fitness
small, mobile so it can find and fertilize the egg
which gender makes more
females make fewer eggs than male (who make lots of sperm)
another word for egg
ovules
another word for sperm
pollen
what defines sexes
difference in gamete size
what do males make
small, less costly gametesw
what do females make
large, more costly gametes
what is another example of dimorphism
sexual dimorphism
what is sexual dimorphism
sexes of the same species exhibit diff morphological characteristics (not characteristics involved in reproduction)
what do anglerfishes have
extreme sexual dimorphism
what do male anglerfishes do
bite and attaches himself permanently to a female
what happens when male anglerfishes attaches to female
his body fuses with hers, his organs degenerate except for his testes, which grow to fill most of his body
how many mechanisms do animals have which determine an individual’s sex
a variety of mechanisms
what do all mammals have
XY system of sex determination
what is the XY system of sex determination
males are heterogametic sex (XY), females are homogametic (XX)
do all vertebrates have XY system of sex determination
nope
what system of sex determination do birds have
ZW; females are heterogametic (ZW), males are homogametic (ZZ)
what is most common sexual system in teleost fishes
hermaphroditism
what are hymenoptera
ants, bees, wasps, etc.
how do hymenoptera and acari (mites) determine sex
haploploidy
what is haploploidy
sex determination system where males develop from unfertilized eggs and are haploid; females develop from fertilized eggs, are diploid
describe males in haploploidy
develop from unfertilized eggs –> haploid
describe females in haploploidy
develop from fertilized eggs –> diploid
what are sex determination strategies in plants
2 major sex determination strategies: some plants are dioecious, others are monoecious
what are dioecious plants
(means 2 houses); individual plants are either male or female (and have either male or female flowers)
another definition of dioecious
male and female sex organs found in separate individuals
what are monoecious plants
hermaphroditisim; one house –> both male and female sex organs on the flowers
what have plants evolved
evolved dioecy (male/female sex organs on diff individuals) multiple times from monoecy (hermaphroditism)
what else have plants evolved
have evolved sex chromosomes multiple times
how is sex determined in turtles and crocodilians
environmental factors; environmental sex determination
what is environmental sex determination
sex is determined by temperature during egg developmnet
are the temperatures that alter sex ratios the same for all species
no; diff species have diff temps
how can the sex ratio evolve (for environmental sex determination)
by females changing where they lay their eggs / females evolving diff preferences for where they lay their eggs
what sex determination system do we see in ants, bees, waps
haplodiploid sex determination
what is haplodiploid sex determination for females
females are diploid, produce haploid eggs via meiosis
what is haplodiploid sex determination for males
males are haploid, produce haploid sperm without meiosis
what does fertilization do in haplodiploid sex determination
fertilization produces diploid female bees
what do unfertilized eggs do in haplodiploid sex determination
produce haploid male bees
how do females determine sex ratio in haplodiploid sex determination
by altering number of offspring resulting from fertilization
what ratio do we see in most species w/ separate sexes
1:1 sex ratio
what happens if one sex is rarer
newborns of that sex more likely to find mates than common sex
what happens to parents w/ genetic tendency to have offspring of rarer sex
will have more grandchildren than average
what happens to alleles for that tendency
alleles will spread, sex ratio will shift back to 1:1, where this tendency is no longer favor
what are other strategies besides 1:1
sequential hermaphrodites
describe uneven sex ratio
initially females produce more daughters than sones. then single female has a mutation causing her to produce only sons. mutation increases in frequency, spreads until equal sex ratio, 1:1 (equal numbers of males and females)
what happens to this mutation at equilibrium
mutation more common in males, because females w/ mutation produce only sons but males w/ mutation produce both sons and daughters that carry mutation
what traits evolved via sexual selection
traits not related to natural selection, maybe even inhibited survival and thus reproduction
what are two classes of sexual traits
primary and secondary sexual traits
what are primary traits
necessary for reproduction to occur
examples of primary traits
structures such as gonads and genitalia
what are secondary traits
strange, gaudy, increase the probability of mating
do secondary sexual traits play a role in reproduction
nope, only indirect role
example of secondary sexual traits
male peacock’s train
what are genitalia on slugs (what kind of trait)
primary sexual trait
what kinda trait is bright colored butt of male mandrill
secondary sexual trait
what did darwin propose about secondary sexual traits
evolved b/c of competition for mates among individuals of same sex or through mate choice (females preference for male secondary sexual traits)
describe secondary sexual traits evolving cuz of competition for mates among individuals of same sex
male-male competition; male prevents other males from mating and this helps him to leave more copies of his genes to the next generation
what is mate choice
female preference for male secondary sexual traits
who came up w/ idea of sexual selection
Darwin
what was Darwin’s idea of sexual selection
special case of natural selection
what do other scientists say about sexual selection w/r to natural selection
they say it is a separate force
what can sexual selection act on
primary or secondary sexual traits
how can traits evolve by sexual selection
if it increases overall fitness, even if it decreases survival
basically what is secondary selection
differential reproduction as a result of variation in the ability to obtain mates
another definition of sexual selection
mode of nat selection where members of one sex choose members of opposite sex to mate with, and compete with members of same sex for access
2 examples of sexual selection
female choice, male-male competition
experimental test of sexual selection
male long-tailed widowbirds have long tail feathers; shortened in one group and lengthened in another. long tailed males had greatest success
do males and females in population have same average reproductive success
yes
what do males and females differ in
reproductive variance among members of each sex
what do differences in the selection gradient result in
sexual dimorphism
what happens when males are subject to stronger sexual selection than females
males will evolve secondary sexual characters that result in marked differences b/w sexes
what do male peacocks do
don’t provide parental care
what leads to marked dimorphism in male peackocks
some males more successful than others who may never reproduce
what happens when males contribute to offspring care
selection gradient is lower, sexes are monomorphic
what species contributes to offspring care
male albatross
what are many seabirds
monogamous, raise offspring together, and sexes are indistinguishable
what happens when males provide all the parental care
selection gradient is reverse, and females compete for access to male
what happens when gradient is reversed and females compete
reverse sexual dimorphism
example of reversed sexual dimorphism
females are brightly colored
what species provide all parental care, and females compete for access to males
red-necked phalaropes
describe female red-necked phalaropes
females are larger and more aggressive; polyandrous, mate w/ many males
what is trade-offs
selection favors display that maximizes a males lifetime fitness
what are trade-offs a tug of war between
two fitness components: survival and mating success
what does compromise ultimately maximize
a male’s lifetime fitness
what is male survival maximized by
a tail length that optimizes aerodynamics, leading to stabilizing selection for tails of intermediate length
what does male mating success depend on
mean female mating preference
what happens if most females prefer long tails
males w/ long tails have greatest mating success [tails will evolve to an equilibrium that is longer than what maximizes survival]
what happens if most females prefer short tails
tails will evolve to a length shorter than what maximizes survival
when does the optimum shift
if strength of natural selection or sexual selection changes
what did darwin say about exaggerated secondary sexual traits
decrease survival
what else can calls attract besides mates
predators
are signals always costly? what does this cause
tug of war between survival and mating success, between effects of secondary sexual traits on survival and mating success
so are these signals always costly
maybe?
what does rick prum argue
beauty evolves cuz of female choice, not necessarily costly or indicative of male fitness potential
what is bateman’s principle asking
why do we usually see males w/ exaggerated secondary sexual traits?
what 3 principles did bateman derive
males have greater variance in number of offspring (reproductive success), greater variance in number of sexual partners (mating success), AND stronger relationship b/w RS and MS in males
why do we usually see males w/ exaggerated secondary sexual traits?
female can fertilize all eggs w/ single mating, so no fitness/selective advantage from a trait to increase number of mates
another reason we see males w/ exaggerated secondary sexual traits
males produce lots of sperm. sexual selection can act more on males than females, because males gain from traits that increase mating success. [-Sexual selection can act more readily on males than females: because selection generally will act to increase the number of mates a male can acquire]
what is operational sex ratio
relative number of males and females available to mate
what is outcome of sexual selection influenced by
operational sex ratio
when do we see sex role reversal
when more females are available, and they are not a limiting resource
basically when do we see sex role reversal
most common sex must compete for access to less common sex
what is this a case of
reversal of bateman’s principle
example of reversal of bateman’s pirnicple
female red phalaropes fight over smaller duller plumaged male on breeding ground; females court males who care for young. AND. male australian seahorse giving birth from his pouch; males choose which courting females will lay eggs in their pouches
what are 2 specific modes of Darwin’s sexual selection
intrasexual competition, intersexual selection
intrasexual competition
male-male competition
intersexual selection
female choice
example of male-male competition
male bighorn sheep competing for access to females; male stag beetles fighting to defend sites where females lay eggs, and they mate w. females. male elephant seals guard harems of females w/ which they sire offspring
how else do males compete
alternative mating strategies
3 male strategies
alpha blocks entrance, beta male sneakily mimic females, gamma males sneak past alpha male
what do alpha males do
large; guard harem of females by blocking the entrance
what do beta males do
medium size; imitates females
what do gamma males do
small size; try to reach females by slipping past alpha male
how do beta male and gamma male gain access to females
by tricking alpha males
how can males interfere w/ each others reproduction
sperm competition
what is sperm competition a way for
males to interfere w/ each others reproduction
how do damselflies mate
when they mate, claspers on male’s abdomen grasp female behind her head. she curls her abdomen so that opening of her oviduct makes contact w/ males penis.
give the example of sperm competition in males
scoop like structure on male’s penis removes sperm of males that copulated w/ female. basically they use this structure to remove sperm of a female’s previous mates before depositing his own
can sperm competition happen in mammals
yup
describe how females of some primates mate w/ males
they mate w/ many males
describe sperm competition in chimpanzees/primates
males have evolved large testicles to produce more sperm
which chimpanzees produce most offspring
individuals w/ most sperm
what can organisms optimize
copulation
what does optimizing copulation do
optimizes fertilization
how can we predict duration of copulation by male dungly
from proportion of eggs fertilized as a function of copulation time, and time it takes to search for and guard female
what is another male strategy
infanticide
where does infanticide occur
mammals, including lions
describe infanticide in lions
male lion has killed a cub after displacing cub’s father and other adult males. females w/ cubs don’t go into heat. when new males takeover a pride they kill the young so that females in pride become fertile again, increasing male’s fitness.
are extravagant male secondary sexual traits (like bright plumage) useful for male-male competition
nope
what is the point of these extravagant secondary sexual traits
help attract females and persuading them to mate –> female choice
describe evidence of sexual selection
simple nervous systems; don’t actually make a conscious choice
what does ‘choice’ refer to
any phenotype of female that biases the type of male she will mate with
what does female choice require
genetically based phenotypic variation in females and males
can mating preferences evolve
yup
what do females of closely related species have
innate preference for mating w/ their own species, which have evolved since divergence from most recent common ancestor
what does avoiding mating with another species do
increases fitness
why does avoiding mating w/ another species increase fitness
hybrids have low viability/fertility
what is sexual selection the cause of
suite of crazy male secondary sexual traits (due to female choice)
describe Leks
females visit lek, mate w/ male of their choice, rear offspring w/o help of males.
what ways do females evolve preferences for male secondary sexual traits
direct benefits, pleiotropic effects, perceptual bias, good genes, fisher’s runaway
what are direct benefits
sometimes males provide direct benefits to females; cricket places spermatophore which female eats, resources like food and care for young that increases female survival and reproductive success
another example of direct benefits
some insects and spiders, male allows itself to be eaten by female after mating
what is pleiotropy
single gene producing multiple effects
what do female guppies prefer
females prefer males w/ more orange in their body
what are guppies attracted to and why
small orange disks, because they feed on small orange fruits and this has translated to females preferring orange colored males
what male guppies have higher fitness
males w/ more orange
describe pleiotropic effect in guppies
guppies prefer orange males b/c they are also attracted to orange fruit for feeding
what are perceptual biases
mating preferences caused by pleiotropic effects
what can females be attracted to
signals that males of their species don’t make and are therefore a side effect of features of nervous system –> epiphenomenon
what are some female mating prefernces
perceptual biases that evolved before origin of male trait on which they act
describe trait evolving via a perceptual bias
male swordtails have dramatic swords that attract females. males of diff species lack the sword, but females prefer males w/ sword that has been surgically added.
describe how the preference of sword evolved
preference for sword evolved before sword itself did
what is good genes
a way that female choice might evolve
define good genes
male traits are advertising to females that the male has good genes
describe good genes in sticklebacks
percentage of sticklebacks that became infected when exposed to tapeworm declined w/ intensity of their father’s red coloration
what do red male sticklebacks have
red males are attracted to females, have alleles that make them resistant to tapeworms and passed on to offspring
describe its indirect effe t
the female preference allele is in linkage disequilibrium w/ alleles at other loci that are under direct selection (alleles related to tapeworm resistance)
describe fisher’s runaway sexual selection model
females w/ preference for long tails mate w/ long tails. offspring have genes for long tail and for preference of long tail.
what are genes for the male trait and female trait in
in linkage disequilbrium (statistically associated w/ each other)
what does Fisher’s model say about these tails
can cause a feedback loop favoring longer and longer tails & preference for them
is fisher’s model actually observed
no; nat selection would balance sexual selection at some point otherwise species would go extinct
why do we see unique features in plants
they have passive fertilization via pollinators
what are these unique features a result of
sexual selection
what are most flowering plants
hermaphrodites
describe operational sex ratio of flowering plants
biased towards males
why is operational sex ratio of plants male biased
b/c after a plant’s ovules are fertilized, it keeps sending out pollen to other plnats
what else do individual plants have
better floral displays
why do individual plants have better floral displays
to compete for pollinators
is having males in a species costly
it seems like it but not actually
why do males seem costly
finding mates takes time & energy, increases risk of predation, parasitism, disease, injury, sex reproduction reduces avg fitness fo offspring, males don’t provide resources to next gen AND females invest half of their resources in producing males.
when do we see male-male competition in plants
pollen grains racing to fertilize ovule (similar to sperm compmetition in animals)
what is benefit to sexual reproduction
increases genetic variation through recombination, allows faster adaptation
what is parthenogenesis
reproduction by making genetic clones of themselves
why must sex have substantial advantage
because parthenogenesis is rare
what is two-fold cost o fmales
males don’t give brith, so population growth rate is halved if there are males
what happens in parthenogenesis
sexual individuals replace themselves, and asexual individuals double their reproduction (produce 2 offspring, 1 male and 1 female).
what happens if there is a mutation that causes females to reproduce asexually
it will spread to fixation quickly
what does the fact that asexuality is so rare suggest
there must be strong advantage for reproducing sexually to compensate for two-fold cost of producing males
what does mutation encoding for asexual reproduction do
spreads to fixation in a few generations (so rarity of asexuality is notable)
what is one advantage of sexual reproduction
recombination produces genotypes and phenotypes that may be better able to fend off pathogens
what is red queen hypothesis
host must run constantly to stay in same place resect to its parasites
basically what is red queen hypotehsis
evolutionary arms race b/w a host and its pathogens
what is red queen hypothesis a metaphor for
evolutionary arms race (host-pathogen evolutionary arms race)
what does red queen hypothesis explain
the evolution of sex in response to an arms race w/ pathogens
basically what is red-queen hypothesis
organisms must continuously adapt and evolve to survive while pitted against ever-evolving opposing organisms in a constantly changing environment
who came up w/ red queen hypothesis
leigh van halen
what does red queen hypothesis predict
attacks by parasites give an evolutionary advantage to sexual reproduction
why do sexual females in NZ mud snails have higher fitness
b/c lower rates of infection by parasites
what do populations exposed to higher densities of parasites have
higher frequencies of sexually reproducing individuals
who has higher fitness, sexual or asexual females
sexual femalse
what happens to these snails (specifically sexual females)
overcome two-fold cost of producing males b/c sexual reproduction has an advantage w/r to arms race against pathogens
what do attacks by parasites do
give evolutionary advantage fo sexual reproduction in NZ mud snail
sexual reproduction allows
exchange of genetic material
where is sexual reproduction found
most organisms
what kinda gametes do males have (what size)
small gametes
describe size of female gametes
larger
what does this difference in size of gametes b/w males and females lead to
diff fitness strategies and sexual selection
what is sexual selection (what types)
male-male competition or female choice
can role reversals in sexual selection occur
yup
what sex ratio is present in most species
1:2
what does sex do to population growth
slows rate of population growth 2x
so what must happen because sex is so common
must have strong benefits
what does recombination allwo
allows much faster adaptation in changing environment (like evolutionary arms race w/ pathogens)
