week 3 vocab Flashcards
example of organisms with sex roles reversed
jacanas or seahorse
male incubates egg (more energetically invested), female compete and are more aggressive
sexual selection occurs when:
there’s a heritable variation of a trait that influences mating success or fertilization success
which sex often experiences stronger sexual selection?
the competing sex,
logic: non-competing can get with whoever they want, but competing one is limited. there’s more selective pressure on the limited one
elaborate traits usually occur in the ___ sex
competing
sexual selection can occur:
before or during/after sex
intrasexually or intersexually
example of intrasexual selection before mating
mooses
male-male or female-female competition for access
example of intersexual selection before sex
peacocks
display by competing sex for mating choice by non-competing sex
example of intrasexual selection d/a sex
frogs
compete to have their sperm fertilize egg
example of intersexual selection d/a sex
“cryptic mate choice”
female chicken can choose which sperm fertilizes their egg
intrasexual selection
individuals within a sex compete DIRECTLY for access to mates and their gametes
examples of evolution of traits for intrasexual selection
weaponry, fast sperm, sexual size dimorphism (competing sex is larger)
sexual size dimorphism
competing sex is larger
intersexual selection
indirect competition for access to mates and their gametes
what traits can help intersexually selecting organisms win access to mates?
mating displays and signals, courtship behavior, or genitalia
sexual selection is the result of:
direct or indirect competition for mates
benefits of sexual reproduction must ___ ___ ___
overcome non-trivial costs
pros of only passing on 1/2 of genetic material must be better than cons of potentially risking survival (colors of guppies finding balance between mating visibility and predation avoidance)
sexual selection often results in traits that ___ natural selection
oppose
where does natural variation come from?
mutations!
process of including mutation in population
created, generates alleles, natural selection hopefully favors it, adaptive trait selected
selection ___ ___ ___
edits existing variation
genes are:
composed of DNA and specify how to build proteins
what are mutations caused by?
DNA copying errors, chemicals, or ionizing radiation
what is important about ionizing radiation?
it can’t affect gametes!
frequencies of mutations can change due to:
meiosis/recombination, natural selection, genetic drift, or gene flow
mechanisms that DECREASE variation
stabilizing selection, inbreeding, and genetic drift
“silent” or “synonymous” mutations
don’t change the amino acid
“nonsynonymous” mutations
change the amino acids and potentially the function of the following protein, can then be acted upon by NS
what are the structural mutations that can occur?
deletion, duplication, inversion, fission, or fusion
mutation rates are very low! so…
mutations likely won’t change allele frequencies in one generation
recombination during meiosis can…
exchange maternal and paternal chromosomes to produce new combinations more rapidly
what is the molecular clock?
Kimura’s theory that most mutations are neutral
we accumulate mutations constantly and we can use that to date how long ago different populations diverged
a lot of DNA isn’t used much (has since been disproven) and mutations of third codon don’t always have an impact
phenotypic plasticity
a change in an individual’s PHENOTYPE in response to their environment
natural selection example:
soapberry bugs
introduction of new host plants with different fruit sizes, bugs shifted hosts
NS resulted in beak adaptation to reach seed
what are the types of selection?
directional, disruptive, and stabilizing
directional selection
individuals with one extreme heritable trait are favored over others
example of directional stabilization
Darwin’s finches in the drought
stabilizing selection
individuals with intermediate trait are favored
example of stabilizing selection
gall-making flies
larvae produce galls on goldenrod plants, but large and small galls were targeted by predation, so intermediate size was favored
disruptive selection
individuals at either extreme of a phenotype are favored
example of disruptive selection
african seedcrackers (birds)
small beaks can eat soft seeds, large can eat hard, but medium aren’t optimal for either
what does stabilizing selection do?
maintain mean and reduce variance
what does disruptive selection do?
maintain mean and increase trait variance
what does directional selection do?
change mean and potentially reduce trait variation
sexual selection
selection due to within-population competition for access to mates and their gametes
sexual selection is responsible for:
more diverse and extravagant traits in nature, rapid evolution, and increased speciation
anthropomorphism
attributing human traits or intentions to non-human entities
innate tendency that we should avoid with this content
sexual selection occurs as a result of ___
variation in mating success
not everyone gets to mate or the same amount of mates
what causes variations in mating success?
competition
gametes are the ____
main difference between males in female
egg
large and sessile gametes
sperm
small and mobile gamete
sexual possibilities:
none (no gametes), two separate sexes (lions), hermaphroditism, sequential hermaphroditism
hemaphroditism
male and female gametes are produced in the same individual
common in plants
sequential hermaphroditism
individuals start life as one sex and later transition into the other
sex roles
dependent on differences in parental investment between the sexes
higher parental investment ->
limiting sex, has mating preferences
lower parental investment
limited sex, has mating competition
anisogamy
differences in gamete size
our ancestral state is ___
isogamy
isogamy
single mating type, everyone can mate with everyone else
all gametes same size
universal compatibility
gamete trade-offs
large but slow/non-moving gamete with lots of resources vs. small but faster gamete with little resources
anisogamy is ___ distributed
disruptively
Bateman’s principle
in most species, females invest more in reproduction than males, making them the limiting sex
male lifetime fitness is limited by…
how many mates they can obtain
female lifetime fitness is limited by…
how much resources they have available to allocate reproduction
result of Bateman’s principle?
females can be the more choosy sex and males have to compete for them
roles can be reversed!
can phenotypic plasticity evolve?
yes, it can be an adaptation
ability to get fit more efficiently is heritable, but looking fit is not a heritable trait
reaction norm
range of phenotypic expressions of genotype across range of environments
example of phenotypic plasticity
male horned beetles
use horns and body size to fight for females
morphology determined by amount of food in larval period (small horns and body or large horns and body)
why spend resources on large horns with small body if you’ll lose anyways?
common garden experiment
individuals with different phenotypes are grown under same conditions
genetically controlled in CGE if…
individuals maintain their wild traits
phenotypic plasticity in CGE if…
individuals shift to similar traits
what is the purpose of common garden experiment?
distinguishing genetic variation from phenotypic plasticity
what are mechanisms that maintain genetic variation?
meiosis/recombination, natural selection, gene flow, disruptive selection, negative frequency-dependent selection
mechanisms that decrease genetic variation
stabilizing selection, inbreeding, genetic drift, positive frequency-dependent selection
frequency dependent selection
fitness of individual is dependent on its relative frequency amongst the population
positive frequency-dependent selection
majority phenotype wins, reduces genetic variation in population
example of positive frequency-dependent selection
poisonous butterflies favoring locally common butterflies of other poisonous ones
mullerian mimicry
two poisonous species mimic each other
whatever looks like this won’t get eaten
negative frequency-dependent selection
minority phenotype wins, promotes genotypic and phenotypic variation in population
example of negative frequency-dependent selection
purple/yellow morph flowers
naive pollinators will switch between then as they find new reward (nectar/pollen)
sampling effects
changes in allele frequency over time that are random with respect to their function or selection
founder effect
loss of genetic diversity bc of migration even in which smaller group “founds” their own population
example of founder effect
less genetic diversity as humans spread out from Africa
bottleneck effects
loss of genetic variation from dramatic reduction in population size and then recovery from it, new population descends from small number
example of bottleneck effect
northern elephant seals
hunting reduced population to 20-40 individuals, today have extremely low genetic variation
genetic drift
changes in allele frequencies in population due to chance events
random effects can lead to…
differences in numbers, sex ratio, or survival of offspring
genetic drift leads to…
evolution at random
example of genetic drift
beetles being crushed by shoe images
4 conclusions about genetic drift
its unbiased, affects smaller populations more, decreases genetic diversity over time, and generates divergence among populations
imagine plots of multi-colored lines
