Final exam Flashcards
natural selection
heritable differences in survival and reproduction in a population
sexual selection
a subset of natural selection that acts on heritable traits affecting reproduction, ability to attract mate
Primary sexual characteristics
genitalia and reproductive organs differentiating males and females, affected by sexual selection
secondary sexual characteristics
differences between males and females that are not directly involved in reproduction, often decorative to attract mates
In which two ways does sexual selection operate in
intrasexual selection and intersexual selection
intrasexual selection
members of same sex compete each other for access to other sex, “male male” competition, favors evolution of weapons
eg: horns on dung beatles
intersexual selection
one sex selects other for reproduction, ‘female mate choice’, favors evolution of ornaments
eg: peacock tail
why are there two sexes?
gametes determine sex
male gametes: small motile gametes, cheep
female gametes: larger, immotile gametes, more expensive
anisogamy
animals with males and females, difference size gametes
isogamy
animals all produce same size gametes
Why are females normally choosy?`
Bateman hypothesis: male reproductive success is limited by number of eggs, male reproductive success is limited by number of mates, so females are choosier bc there is more competition for female gametes
parental investment theory
the sex that pays the highest cost should be choosier, this is usually females (incubation, feeding etc)
sex role reversal
when females compete for males that invest heavily in parental care and males are choosy
what happens during sex role reversal
females develop ornaments and weapons
eg: pipefish and seahorses (get preggo)
how can you tell who is choosier
animals with ornaments and weapons are often not the ones choosing
How do preferences evolve
1) sensory bias hypothesis
2) direct benefits of mate choice
3) indirect genetic benefits of mate choice
sensory bias hypothesis
Female mating preferences are a product of preexisting biases in females’ sensory system
thus biases evolved in none-mating contexts, males evolved to match pre-existing biases, like food!
eg: trinidadian guppies and the color orange!
direct benefit of mate choice
females can benefit by choosing males that provide direct benefits like food gifts, access to territories with food or enhanced parental care
Nuptial gifts: given to female before mating, provides nutrition
eg: fireflies transfer spermatophore during mating which has lots of protein
Indirect genetic benefits of mate choice
genetic benefits females obtain for their offspring by mating with males with high genetic quality
2 types: fisherman runaway selection and handicap principle/good genes
fisherman runaway selection
male trait coevolves with female preference and becomes increasingly exaggerated
1) female mates with mate with preferred trait
2) sons inherit trait, daughters inherit preference
3) strength of trait and preference increase (runaway) until costs outweigh the benefits.
assumes a linkage between gene for trait and preference
found for 23/43 species
handicap principle/ good genes
handicap principle: secondary sexual traits are costly, so only highest quality can display the most extreme forms
‘good genes’’: females benefit from choosing high quality males because offspring will inherit high quality alleles.
european tree frog: males call to attract females, offspring growth correlated with the attractiveness of males (most calls)
precopulatory sexual selection
sexual selection before mating
post-copulatory sexual selection
selection that occurs after mating, effects fertilization success
intrasexual postcopulatory selection
sperm competition between different males to fertilize eggs
intersexual selection
cryptic female choice, female influence over which males sperm fertilizes her eggs
Mate guarding
male follows female around before and after sex to reduce sperm competition and enhance paternity success, but is a lot of time and energy
eg: black throated warblers—> is effective in increasing paternity
eg: damsel flies genitals suck out other sperm, dunnock: when males return they peck at cloak for it to swell and expel sperm
Cryptic female choice
females influence fertilization success of some sperm over others in favor of high quality males
eg: feral fowl: females eject sperm of males that are subordinate, because they often coerce her,
but they still have same mating success
Alternative reproductive male tactics
1) bourgeois tacticL
2) parasitic tactic
Bourgeois tactic
used by competitive males that define territory and posses attractive traits
parasitic tactic
used by less competitive males to steal matings from bourgeois males
types of parasitic male tactics:
satellite males and sneaker males
satellite males
stay near bourgeois males to intercept females
sneaker males
hide from bourgeois males but sneak in to fertilize eggs, often pretend to be females
How do these tactics evolve
conditional strategy hypothesis and evolutionary stable hypothesis
conditional strategy hypothesis:
bourgeois are the highest fitness, and only best condition males poorer condition takes parasitic approach to get some success
basically, males with lower fitness don’t have any choice if they want to survive
eg: green frog calls, satellite males want to be near highest quality males because they want to mate with females the bourgeous males are attracted to
evolutionary stable strategy
two strategies are maintained by frequency dependent relationship. fitness of tactics are higher when rare.
eg: pumpkin seed fish, sneaker males fertilize eggs: prediction is they have the same success, this is true
mate choice copy
a situation in which one individual observes and copies the mating decision of another prob because it is difficult to evaluate male quality if similar of if unexperienced
Trinidadian guppies changed choice to be choice of a model female.
sexual conflict
occurs when males and females have conflicting reproductive interests–> males and females maximize their reproductive fitness in different ways—> associated with nonmonogomous systems,
why harm your mate?
selection doesn’t favor harm itself, selection favors a trade that increases an individuals fitness, and sometimes harm occurs as a byproduct
sexual conflict as infraspecific coevolutionary arms race
male adaption–> costly to female—> female adaptation–> costly to male–> male adaptation etc…
adaptations to sexual conflict
grasping/antigrasping structures (water striders), male harassment(drosophila) /femaleresistance, traumatic insemination(bedbugs)
sexual conflict over fertiliztion
adaptation for sperm competition (seed beetles–> male genetaliea has spines, longer spines have more offspring, puncture reproductive tracts, female developed thickened walls.
copulatory plugs
transferred from males to females during mating, hardens inside female and prevents females from relating, females evolve to dissolve it
toxic seminal proteins
transfers toxic proteins in seminal fluid, increase egg production and makes females less receptive to other males, decreases their lifespan and fecundity
parental care
behaviors of parent to increase offspring fitness, costly to parents, both parents experience same fitness benefits of parental care, parent with highest cost of care should provide less care
female biased parental care
in many mammals and birds, females provide more care because they have more confidence in relationship to offspring while males are more uncertain when fems aren’t monogamous
eg:blue footed booby ( males and females raise offspring together, females mate with others while males are away, males provide less care when its more possible that females have mated with others)
male biased parental care
males provide most care in fish, amphibians and reptiles because fertilization is external (visible) so males are more sure,
indeterminate growth: females care for young less because its more beneficial for them to keep growing
eg: bluegill sunfish (territorial males make nests, females lay eggs in nests, sneaker males go in and quickly try to release sperm.
monogamy evolves when…
biparental care is essential, resources are poorer, rare in mammals bc of lactation eg: california mouse, more survived when both were rpesent
why would monogamy evolve without biparental care
Territorial cooperation hypothesis:
2 individuals can defend territory better, high territory competition, high predation
Male guarding hypothesis: selection favors males who guard females because males done encounter many females
for snapping shrimp: both are true
polygyny mating systems
one male and multiple females
Female aggregations polygyny types
1) female defense polygyny
2) resource defense polygyny
Female Defense polygyny
single male monopolizes group of females, females group bc of predators
Feral horses: defend their band from others, don’t show territory defense
Resource defense polygyny
males defend rich territories that attract groups of females.
Carrion beetles will fight over meat and large males were dominant and mated with more females
male dominance polygyny
males gather in fixed locations (leks) where they display to females, dom males occupy best locations, small number of males mate with multiple females
Why do low rank males lek?
1) hotspot hypothesis: all males should gather where there are lots of females (food is likely there too)
removal of males should not effect attractiveness of lek
peafowl
2) hotshot hypothesis: low rank males should aggregate around high rank males because females are attracted to high rank males
removal of males sshould decrease attractiveness of lek
great snipe
Polyandrous mating systems are predicted to evolve when…
1 female multiple males, are predicted to evolve when biparent care isn’t necessary and parental care is male based, associated with sex role reversal species
Malte Andersson: how can polyandry evolve
1) species with male biased parental care, female may need extensive feeding time (resource poor habitat or predation of offspring)
2) females develop high fecundity and can lay more eggs than 1 male can care for
3) competition among females for males
Jacana fits all of these!
polygynangrous mating systems
multiple males and multiple females rare but occurs in social species "plural breading" predicted to evolve when group defense of territory is more successful than individuals all defend together e.g. european badgers!
promiscuous mating systems
multiple males multiple females, without social groups
when does promiscuity evolve
when benefits of social living is low, pair bonds do not benefit either sex, territory defense is too costly
what is a type of promiscuous mating
scramble competition: individuals compete with one another to find and mate with multiple partners
eg: kelp flies
red squirrels
social vs genetic monogamy
can be social monogamous and genetically not,
eg: songbirds engage in extra pair copulations (EPC), EPC can benefit offspring if mate isn’t high quality so that they can have offspring with better mates
eg: Juncos!
life history traits
traits involved in growth, survival, reproduction
eg: age at first reproduction, number/ size of offspring, amount of parental care, survival rate
life history theory
natural selection favors traits that maximize an individuals lifetime reproductive success (energy and resources are distributed between self and reproduction, tradeoff between own growth and reproduction
Low parental care
low survival, short life span, high fecundidty
high parental care
high survival, long life span, low fecundity
medium parental care
medium fecundity, survivorship and parental care
tradeoff between current and future offspring
energy allocated toward current offspring reduces the energy available for future offspring
parent-offpsirng conflict theory
parents and their offspring have different fitness interests under different selective pressures, parents should maximize lifetime reproductive success, offspring should maximize their own fitness (obtain as much energy/care from parents as possible
optimal level of parental investment is higher for offspring than parent which creates a conflict
consequences of parent-offspring conflict
1) if parental care costs increase, parent should provide less care to current offspring
2) tradeoff between current and future reproduction– parents that invest more in current brood should have higher current reproductive success but reduced future success
eg: treehoppers
brood reduction
the death of some siblings as a result of biased parental care to enhance fitness of surviving siblings- beneficial if resources scarce, some siblings are small or sick
hatching asynchrony
differences in hatching timing when birds lay eggs over multiple days allows parents to modify care based on current conditions, high resources–> all offspring have high prob of survival, low resources, only earliest developed offspring have high prob of survival
eg: yellow headed blackbirds
brood parasitism
a behavior in which a female brood parasite lays an egg ini the nest of another female, reduces parental care,
interspecific brood parasites
females who lay eggs in nests of another species,
obligate interspecific brood parasites
only lay eggs in nests of other species, avoids all costs of parental care –> cuckoos and cowbirds
brood parasitism causes:
a coevolutionary arms race, adapt to recognize own eggs and reject parasites, parasite mimics egg of host better,
hormones regulate parental care:
steroid hormones in mammals, prolactin, estradiol progesterone
rats treated with prolactin showed more parental care
sociality
the tendency to live and associate with others
benefits of sociality
reduce search time for recourses
increased feeding success
enhanced resource defense, reduced creation risk
lower physiological costs (huddling for thermoregulation, increased aerodynamics)
costs of sociality
increase competition for resources, increased predator attraction
increased risk of disease transmission
increased aggression
dominance hierarchies
an organized social system with dominant and subordinate members (can actually minimize aggressive interactions
linear dominance hierarchy
individuals are ranked, dominant to all below, subordinate to all above
eg: charm baboons- reduces aggression
cooperative behavior
mutually beneficial interaction between individuals
altruism
a behavior that increases fitness of recipient and involves a cost to the individual performing the behavior (usually involves kin selection , increase fitness of relatives, and inclusive fitness
inclusive fitness
number of offspring produces + number of offspring produced by relatives
hamilton rule
predicts when altruism should evolve based on benefits to recipient (b), costs to actor (C) and relatedness between recipient and actor
altruism can evolve when BXr> C
belting ground squirrel’s alarm calls, do it more
cooperative reproduction
only a few individuals breed, others do not breed but help care for young
how can cooperative breeding evolve
helpers usually close related to breeding individuals (indirect benefits), and ecological constraints (lack of breeding sites and high predation risk)
castes
morphologically and behaviorally distinct groups of individuals within a social group
eg: large soldiers that defend nest, small workers that care for nest
eusocial species
species that live in social groups and have cooperative breeding with a cast system (subset of individuals
haplodiploid in eusocial species
hymenoptera (wasps bees ants)–> eusociality has evolved multiple times, workers are usually sterile females,
have haplodiploid genetic system, males develop from unfertilized eggs (haploid), females develop from fertilized eggs (diploid)
byproduct mutualism
when an individual’s behavior increases its own fitness and the fitness of others (cooperative behavior is self serving)
direct reciprocal altruism
the actor can benefit if the recipient of an altruistic behavior reciprocates in the future, both eventually receive the benefit
evolution of reciprocal altruism
tit-for-tat strategy: first time interact with new individual: always help
subsequent interactions, match behavior of individual from previous interactions
conditions required for evolution of reciprocal altruism
individuals must interact repeatedly
benefits of receiving help must exceed costs of giving help
individuals must be able to recognize one another to prevent cheating
eg japanese macaques grooming away parasites
parasite
an organism that lives in or on another organism and gets nutrients and shelter from the host at the hosts expense
hyperparacite
a species that parasitizes a paracite
definitive host
a host in which the parasite reproduces
intermediate host
a host in which the parasite growths develops but does not reproduce (must get from intermediate host to definitive host to reproduce
ectoparasites
live on host (external)
endoparasites
live in host (digestive tract, blood etc) most behavior altering parasites are endoparasites
