Chapter 9 Flashcards
Haplodiploidy
sex-determination system where males develop from unfertilized eggs and females develop from fertilized eggs
males develop from unfertilized eggs and are
haploid
females develop from fertilized eggs and are
diploid
sexual reproduction
a reproduction mechanism in which progeny inherit DNA from two parents
a reproduction mechanism in which progeny inherit DNA from two parents
sexual reproduction
gonads
primary sexual organs in animals
how are sexual gametes produced
through meiosis
what does meiosis result in
haploid cells containing a single full set of chromosomes
what do haploid gametes fuse together to produce
diploid zygote
asexual reproduction
reproduction mechanism in which progeny inherit DNA from a single parent
reproduction mechanism in which progeny inherit DNA from a single parent
asexual reproduction
a form of asexual reproduction in which an individual is produced from the nonsexual tissues of a parent
Vegetative reproduction
Vegetative reproduction
a form of asexual reproduction in which an individual is produced from the nonsexual tissues of a parent
clones
individuals that descend asexually from the same parent and bear the same genotype
individuals that descend asexually from the same parent and bear the same genotype
clones
binary fission
reproduction through duplication of genes followed by division of cell into two identical cells
parthenogenesis
asexual reproduction in which an embryo is produced without fertilization
asexual reproduction in which an embryo is produced without fertilization
parthenogenesis
what results in clones
when germ cells develop directly to egg cells
what results when germ cells undergo partial or complete meiosis
genetically variable offspring
benefits of parthenogenesis
- reproduction during times of scarcity
2. genetic stability in constant environments
disadvantages of parthenogenesis
limited genetic variation through recombination and mutations (low adaptability in unstable environments)
costs of sexual reproduction
- sexual organs need energy and resources
2. mating behaviors need time and energy, increase risk of herbivory, predation, and parasitism
cost of meiosis
the 50% reduction in the number of a parent’s genes passed on to the next generation via sexual reproduction versus asexual production; occurs because sexual genes are haploid
what is the cost of meiosis counterbalanced by
hermaphroditism
hermaphroditism
an individual possesses both male and female gametes
how can the costs of sexual reproduction be offset
if the male helps the female take care of offspring, reducing female energy costs
benefits of sexual reproduction
- purging mutations
- coping with environmental variation
- coping with parasites and pathogens
purging mutations
sexually reproducing organisms can lose deleterious mutations during meiosis
- due to random assortment, many gametes will not contain mutations
what will the fusion of two gametes with the same mutation result in
an offspring that is homozygous recessive for that mutation; likely that the offspring will not be viable
what organisms have no means of purging mutations
asexual
coping with environmental variation
offspring are likely to encounter different environmental conditions than their parents did
what do offspring with genetic variation resulting from sexual reproduction have
an increased probability of possessing gene combinations that will help them adapt to different conditions
coping with parasites and pathogens
pathogens have much shorter generation times and larger population sizes than the host species they infect
- this allows pathogens to evolve ways around host defenses and forces hosts to repidly evolve new defenses
Red Queen Hypothesis
sexual selection allows hosts to evolve at a rate that counters the rapid evolution of parasites
perfect flowers
flowers that contain both male and female flowers
simultaneous hermaphrodites
individuals that possess male and female reproductive functions at the same time
individuals that possess male and female reproductive functions at the same time
simultaneous hermaphrodites
individuals that possess male or female reproductive function and then switch to the other
sequential hermaphrodites
sequential hermaphrodites
individuals that possess male or female reproductive function and then switch to the other
monoecious
plants that have separate male and female flowers on the same level
plants that have separate male and female flowers on the same level
monoecioius
plants that contain either only male flowers or only female flowers on a single individual
dioecious
dioecious
plants that contain either only male flowers or only female flowers on a single individual
polygamo-dioecious
having bisexual and male flowers on some plants and bisexual and female flowers on others
having bisexual and male flowers on some plants and bisexual and female flowers on others
polygamo-dioecious
natural selection should favor the strategy with the highest
fitness
if a male can invest in female function while giving up only a small amount of male fitness (or vice versa), selection should favor
hermaphroditism
when does self-fertilization (selfing) occur for hermaphrodites
when an individual’s male gametes fertilize its own female gametes
selfing poses a cost due to
inbreeding depression
since self-fertilization poses a cost due to inbreeding depression, what should selection favor
individuals that can breed with other individuals (outcrossing) when possible
how does sequential hermaphroditism avoid the problem of selfing
by separating sexual functions in time
What do some species have that prevents organisms from being able to self
self-incompatibility genes
some species can switch between
outcrossing and selfing
What happens when mates are available
individuals outcross
what happens when mates are unavailable
individuals self-fertilize
what does self-fertilization produce
less viable offspring (better than nothing)
what can mixed mating be in response to
a lack of resources in the environment
in organisms with separate sexes, what is the typical sex ratio of male to female offspring
1:1
what is sex determined by
inheritance of sex-specific chromosomes
XX
females
XY
males
what will the sex that possesses two different chromosomes produce
approximately equal number of gametes with each chromosome
in some, what is sex determined by
the presence or absence of a sex-specific chromosome
In bees, ants, and wasps, what is sex determined by
whether or not eggs are fertilized
Environmental sex determination
a process in which sex is determined mostly by the environment
a process in which sex is determined mostly by the environment
environmental sex determination
type of phenotypic plasticity, where phenotype is sex
environmental sex determination
frequency dependent selection
when the rarer sex in a population is favored by natural selection
when the rarer sex in a population is favored by natural selection
frequency dependent selection
in a population with an uneven sex ratio, what will the rarer sex do
compete with fewer individuals for breeding
what is the consequence of the rarer sex competing with fewer individuals for breeding
the rarer sex will experience higher fitness
what will mothers that produce the rarer sex experience and why
increased fitness because her offspring will produce more offspring (selection should favor a mother that produces the rarer sex
what happens as selection causes the rare sex to become common
the sex ratio of the population will eventually become even
when may skewed sex ratios occur
with local mate competition
local mate competition
competiton for mates occurs in a very limited area, and only a few males are required to fertilize all of the females
mating system
the number of mates each individual has and the relationship with those mates
the number of mates each individual has and the relationship with those mates
mating system
what does a female’s reproductive success depend on
how many eggs she can produce and mate quality
what does a male’s success depend on
the number of females he can fertilize
promiscuity
males mate with multiple females and females mate with multiple males and do not create lasting social bonds; common among animals and outcrossing plants
males mate with multiple females and females mate with multiple males and do not create lasting social bonds; common among animals and outcrossing plants
promiscuity
what does rampant promiscuity fend off
disease, bad genes, and extinction
the more different males and females look in a species…
the more polygamous they’re likely to be
polygamy
a single individual of one sex forms long-term social bonds with more than one individual of the opposite sex
a single individual of one sex forms long-term social bonds with more than one individual of the opposite sex
polygamy
polygyny
a polygamous mating system in which a male mates with more than one female
a polygamous mating system in which a male mates with more than one female
polygyny
when may polygyny evolve
when males compete for females, or when a male can defend territory and resources
polyandry
a polygamous mating system in which a female mates with more than one male
a polygamous mating system in which a female mates with more than one male
polyandry
when may polyandry evolve
when females search for superior sperm or receive material benefits from each suitor
where can polygyny typically be found
a group with one male and multiple females (humans, gorillas, elk)
who usually provides the majority of parental care in polygynous systems
females
polygyny threshold model
demonstrates the link between female reproductive success and territory quality or the quality of a breeding situation
an explanation for why polygynous systems persist
polygyny threshold model
what does the polygyny threshold model also show
the effects of female reproductive success when multiple females in the same territory mate with one male
monogamy
when a social bond between a male and female persists through the period that is required for them to rear offspring
when is monogamy favored
when males make important contributions in raising offspring
extra-pair copulation
when an individual that has a social bond with a mate also breeds with other individuals
why do females use extra-pair copulation strategy
to obtain superior genotypes an dproduce offspring with better genetics
mate guarding
one partner prevents the other partner from participating in extra-pair copulations
sexual selection
natural selection for sex-specific traits that are related to reproduction; leads to a variety of differences between males and females
sexual dimorphism
the difference in the phenotype between males and females of the same species (body size, courtship behavior)
primary sexual characteristics
traits related to fertilization
secondary sexual characteristics
traits related to differences between the sexes in terms of body size, ornaments, color, and courtship
what do female preference for male traits relate to
features that improve her fitness, such as material benefits (e.g., high-quality territory)
good genes hypothesis
an individual chooses a mate that possesses a superior genotype
good health hypothesis
an individual chooses the healthiest mates
runaway sexual selection
selection for preference of a sexual trait and selection for that trait continue to reinforce each other; continues until males run out of genetic variation
extreme traits
burden males by requiring energy and resources, and attracting predators
the handicap principle
the greater the handicap an individual carries, the greater its ability must be to offset that trait
