Exam Two Prep Flashcards
how to measure heritable variation
phenotype = genotypic effects + enviornmental effects
Vp = Vg + Eg
how is genetic variance broken down
Va= additive genetic variance
Vd= dominance variance
Vi= epistatic variance
additive genetic variance
Va
variation due to additive effects of alleles at aall relevant loci
- inherritance of alleles
dominance variance
Vd
variation associated with interactions between alleles at a specific locus
affects the phenotype derived from genes, not affected by how genes are inherited
epistatic variance
Vi
genetic variation associated with non-additive interactions between different alleles in different loci
heritabillity
h^2
proportion of the variance in phenotype that is transmissible from parents to offspring
influenced by natural selection
heritabillity ranges from 0 to 1,
heritabillity= 1 trait influenced by genetics only
heritabillity = 0 trait influenced by environment
what are the measures of heritabillity?
broad sense heritabillity (H)
narrow sense heritabillity (h^2)
broad sense heritabillity (H)
measures the proportion of phenotypic variation due to genetic effects
easy to measure less informative
H= genetic variance/phenotypic variance
narrow sense heritabillity (h^2)
determines the degree to which offspring resemble their parents
harder to measure more informative
h^2= additive genetic variance/phenotypic variance
on a linear graph what is the heritabillity?
the slope is the heritabillity
Breeder’s equation
R=(h^2)(S)
can be used to predict the response to direction selection on a trait
R= response to selection
S= Selection differential
h^2= heritabillity
artificial selection
“managed evolution” practice of selecting a group of organisms from a population to become the parents of the next
truncation point
cut off level of phenotype that determines which individuals will be used for breeding purposes
Selection differential (S)
the difference between mean length of the breeders and mean length of the inital population
strength of selection
Response to selection (R)
difference between mean length before and after selection
breeder’s equation rearranged for heritabillity
h^2=R/S
or
h^2= (next gen - original)/(selected- original)
modes of selection
effects of natural selction on the distribution of a trait
what are the three modes of selection
directional
stabilizing
disruptive
directional selection
fitness consitently increases (or decr.) with the value of a trait
mean value of trait will increase or decrease
stabilizing selection
selection favors intermediate trait
variation of the continuous trait is** reduced**
doesn’t change mean value of trait
disruptive selection
selection favors extreme phenotypes
variation of trait increases
doesn’t change mean value of a trait
may lead to speciation
species
smallest evolutionarily independent unit, basic unit of classification
what consititutes a species is highly debated
biological species concept
a species is a group of interbreeding natural populations that are reproductively isolated from other groups
reproductive isolation is a mechanism of preventing two species from producing viable, fertile offspring
types of reproductive barriers
prezygotic and postzygotic
prezygotic reproductive barriers
prevent mating or fertilization from happening
examples: habitat isolation, behavioral isolation, temporal isolation, mechanical isolation, gametic isolation
example of
habitat isolation
parasites living on different hosts
example of
temporal isolation
plants that flower at different times, insects that emerge at different times of year
example of
behavioral isolation
different mating calls or dances
example of
mechanical isolation
structural differences that prevent mating
example of
gametic isolation
sperm of one species cannot fertilize eggs of another
postzygotic reproductive barriers
prevent a hybird zygote from developing into a viable, fertile adult
prevent the formation of fertile offspring even if mating does occur
reduces hybrid viabillity and fertillity
problems of biological species concept
- not applicable to asexual organisms
- difficult to apply in “real world”
- not applicable to extinct organisms
morphological species concept
species are sets of organims that ** look similar ** to each other and distinct from others
problems with morphological species concept
- descriptions of morphological characteristics are subjective
- some morphological characters may not reflect evolutionary theory
- not applicable to organims that are morpholocially indistinguishable but are clearly different lineages
as per 2. an example would be traits produced by convergent evolution
phylogenetic species concept
species are the smallest monophyletic group on evolutionary tree
problems with phylogenetic species concept
- phylogenies are often unknown
- cut off for a species is often arbitrary
as per 2. how much genetic distinctiveness is required to seperate one species from another
general lineage concept
species are evolving metapopulation lineages
species criterions dont typically arise at the same time or order
attempts to unify all other species concepts
under the general lineage concept
species criterions (SC)
evidence for lineage diversification
ex- reproductive incompatible
gentic differention
morphologically distinct
lineage
lineal descedent from an ancestor
allopatric speciation
speciation involving geographical separation of populations
geographical isolation
physical barrier prevents genetic exchange
basically allopatric
types of geographical isolation
- isolation by dispersal
- isolation by vicariance
geographic isolation by dispersal
dispersal (migration) past the barrier
can cause founder event
geographic seperation by vicariance
when a new geographical barrier appears and seperates a once continuous population
ring species
new species can arise through circular overlap without limiting gene flow
think about the salamanders aroudn the mountains
parapatric speciation
speciation event occurs in continuously distributed population without disninct geographical isolation
a hybrid zone is formed
VERY RARE
sympatric speciation
new species evolve from common ancestor w/o geographical isolation
for sympatric speciation
examples of isolation mechanisms
- habitat isolation
- temporal isolation
- behavioral isolation
- polyploidy
polyploidization
whole genome is duplicated and double chromosome #
offspring unable to breed with parental species
two types: autopolyploids and allopolyploids
CAUSES SYMPATRIC SPECIATION
autopolyploids
genome duplication within a species
individuals have extra set of chromosmes from SAME parental species
allopolyploids
genome duplication in a hybrid
individuals have extra set of chromosomes from DIFFERENT species
How would hybridization affect speciation?
A. Hybridization may slow or reverse differentiation by
allowing gene flow and recombination.
B. Hybridization may accelerate speciation via promoting
adaptive divergence through gene introgression.
C. Hybridization may cause speciation by
allopolyploidization.
D. All of the above.
D. All of the above
seperation caused by geographical isolation
- seperation
- divergence
- reproductive isolation
in terms of speciation caused by geographical isolation
seperation
genetic isolation of populations, some form of physical isolation prevents gene flow
in terms of speciation caused by geographical isolation
divergence
differentiation among populations, due to natural selection or genetic drift
in terms of speciation caused by geographical isolation
reproductive isolation
if physical barrier is removed, populations cannot interbreed
phylogeny
evolutionary history of a group of organisms
phylogenetic ( or evolutionary ) tree
graphical summary of evolutionary hsitory
what does an evolutionary tree demonstrate?
- hypotheses about relatedness and common ancestry
- timing of evolutionary modifications (transitions) that occured
of a phylogenetic tree
root
ancestral taxon where all other nodes descend
of a phylogenetic tree
tips
descendant taxa
basically the modern day species or descendant
of a phylogenetic tree
branches
lineages, linear descend from ancestors
of a phylogenetic tree
nodes
evolutionary branch points, shared ancestors
of a phylogenetic tree
clade
also known as monophyletic group
group of organisms that include a common ancestor and all of its descendants
monophyletic group
also known as a clade
contains single common ancestor and all of its decendants
paraphyletic group
contains an ancestors and some, but not all of its descendants
polyphyletic group
contains some of an ancestor’s decendants not including the ancestor
synamorphy
shared derived character
this is what defines monophyletic groups
traits shared between species because they are homologous and derived from a common ancestor
homoplasy
traits evolved independently in seperate lineages
analogous traits, could evolve throug convergent evolution
apomorphy
derived character
types: synamorhpy and automorphy
autamorphy
unique derived character on a particular taxon
polytomy
when there is multiple splits, evolutionary relationship cannot be fully resolved
principle of parsimony
a preferred phylogenetic tree is one that requires the minimum number of character changes
cost of meiosis
females lose 50% of genetic contribution
problems in phylogeny reconstruction
- convergent evolution leads to analogous traits that do not reflect evolutionary history
- homoplasy- traits that have been gained or lost independently in sperate lineages
multiregional hypothesis
homo erectus evolved in africa and moved into eurasia about two million years ago. homosapiens independently evolved from these
out of africa hypothesis
abt 200,000 years ago modern humans originated in africa, less than 100,000 years ago they spread across the globe
pathenogenesis
offspring developed from unfertilized eggs
allows females to reproduce asexually
costs of breaking adpated genetic combinations
reproducing sexually may disrupt beneficial genetic combination and lower the mean fitness of offspring
costs of sexual reproduction
- cost of meiosis
- cost of males
- costs of breaking adapted genetic combinations
- costs associated with the mating process
look at these from the female perspective
cost of males
males do not provide resource to the next generation, yet femals typically invest half of resources into production from males
cost of having less number of offspring in sexual reproduction due to the production of males
costs associated with the mating process
finding a mate, energy spent on courtship, increased risk of predation
risk of disease transmission and parasite infection
advantages of sexual reproduction
- lottery hypothesis
- muller’s rachet hypothesis
- red queen hypothesis
lottery hypothesis
sexual reproduction allows organisms to produce genetically diverse offspring
some might be able to surrvive better by chance
not supported by empirical data
Muller’s rachet hypothesis
sexual reproduction decreases deletrious mutations through recomination
more data supports this hypthesis
red queen hypothesis
coevolving species maintains a dynamic equillibrium, sexual reproduction can increase host resistance to parasites
sexual dimorphism
distinct difference in size or appearance between the sexes of an organism
anisogamy
fusion of gametes that are dimorphic
term for different sized gametes
males vs females on reproduction
males will specialize on finding mates
females will specialize on parental effort not mating effort
secondary sexual characteristics
characters not needed for surrvival or mating but used for competition for mates or mate attraction
evolved through sexual selection
sexual selection
different reproductive success due to variation among individuals in sucess at getting mates
who is sexual selection more intense towards
more intense on the sex that is specialized on finding mates
this is typically males
sexual selection for males
reproductive success is limted by access to mates
males evovle to compete for mates
intrasexual selection
sexual selection for females
reproductive success is limtied by capacity to produce or raise offspring
females should be choosy
intersexual selection
intrasexual selection
(male-male competition)
compete for breeding territories or access to females
leads to evolution of incr. strength, body size or weaponry
sneaky male strategy
males sneak in to access a femal partner, avoiding more dominant males
intersexual selection
(female choice)
selection on males based on female choice
many of the traits that females are attractive to are actually maladpative for the surrvival of the male
for females how does reproductive success increase
by mating with males that provide direct or indirect benefits
reproductive success
direct benefits
the expression of a male trait may indivate a male’s abillity to provide resources
examples- nupitial gifts, territory, parental care
indirect benefits
the expression of a male trait may indicate genetic quality of a male
why female organisms are choosy?
- may directly benefit when they get resources
- may get better genes for their offspring ( sexy son hypothesis and good genes hypothesis)
- may have preexisitng sensory biases (sensory biases hypothesis)
runaway selection
a secondary sexual trait expressed in one sex becomes genetically correlated with a preference of the trait in the other sex
sexy son hypothesis
this is such a weird name
females with a preference for ornamented males will produce sons ith higher mating success
runaway selection vs sexy son hypothesis
runaway theory explains the evolutionary process how males evolved to have a trait based on female preference
sexy son hypothesis explains why females are choosy
good genes hypothesis
proposes that females select males that have genetic advantages to incr. offspring quality
the male trait that females prefer is a reliable and honest signal of male genetic quality
good genes hypothesis vs. sexy son hypothesis
sexy son hypothesis - females indirectly benefit from producing attractive sons
good genes hypothesis- females prefer males that give good genes to both her sons and daughters
honest signals
example of it at least bc no definition is given
birds that are sick don’t have full colorful plumage,
plumage is an honest signal of male’s current health condiition
handicap principle
suggests that reliable signals must be costly to the signaler
handicap = secondary sexual trait that females prefer, no good for males
handicap has to be costly so it cannot be cheaply imitated
If truly high quality males are more likely to survive with the handicap, then
handicap will be a reliable indicator to represent male’s overall genetic quality
sensory bias hypothesis
females preferences result from biases in female sensory system
examples of reversal in reproductive investment
seahorses, gold specs jawfish and giant water bug
if male investment is higher, males tend to be choosy and females compete
sex determination system
a bio system that determines if an individual is a male, female, or hermaphorodite
what determines whether an individual becomes male or female
- genotypical sex determination
- enviormental sex determination
genotypic sex determination
sex of individual is determined by genotype
ex: mammals, birds, amphibians, most insects, etc
two types: heterogametic sex and homogametic sex
heterogametic sex
the sex that has two different sex chromosmes
homogametic sex
the sex that has one type of sex chromosome
sex determination in mammals
sex is determined by the presence of a Y chromosome
sex determination in birds
sex is determined by the Z and W chromosomes
male = ZZ female ZW
haplodiploidy
males develop from haploid unfertilized eggs. females develop from diploid fertilized zygotes
this is the sex determination mechanism in bees ants and wasps
enviornmental sex determination
influenced by enviornmental cues
cues can be temp, pH, social interactions
ex: many reptiles, some fish
true or false
sex is controlled by one master-switch gene
false, in model organisms yes but multiple genes can influence sex( polygenic sex determination)
hermaphorditism
organism is able to produce both male and female gametes
happens to many fish
types: protandry and protogyny
protandry
organism begins life as a male, changes into a female as it incr. in size
occurs when females gain more in reproductive success as they incr. in size
protogyny
an organism begins life as a female, changes into a male as it incr. in size
occurs when males gain more reproductive sucesss
social behaviors
interaction among individuals of the same species in ways other than mating
can be cooperative or conflicting
actors
individuals that perform social behavior
recipients
individuals that actor interact with
four types of social interactions
- mutual benefit
- selfishness
- altruism
- spite
mutual benefit
both actor and recipient gain fitness
ex: cooperative breeding birds, communal nesting
selfishness
actor acts in a manner that increases its fitness to the demise of another
ex: cannibalism in cane toad- provides nutrients + reduces competition
spite
actor harms its own fitness and the fitness of another
ex: production of bacteria in two e.coli strands
altruism
acting ot increase another individual fitness at a cosst to ones own
ex: alarm calling in bedling’s ground squirrel (trilling)
hamilton’s rule
not the equation
individuals engage in altrusitic behavior if the indirect benefits derived from this act are greater than its cost
hamilton’s rule equation
Br- C>0
B- benefit to recipient
r- coefficient of relatedness
C- cost to the donor
coefficient of relationship
probabillity of the homologous alleles in two indivudals are indentical by descent from recent common ancestor
when r is higher, individuals are more closely related
under hamilton’s rules
fitness has two components
direct fitness- reproductive success of the individuals and their offspring
indirect fitness - reproductive success of the individuals relatives
inclusive fitness
direct and indirect fitness of an individual
kin selection
a process by which a behavioral act is facored due to its beneficial effects on relatives
organisms are more likely to perform altruistic acts toward their relatives
altruistic behavior is a result of kin selection
natural selection that favors indirect fitness of individuals
reciprocal altruism
altruistic behaviors evolved among unrelated individuals through repeated reciprocal interactions
related or unrelated and very rare
an individual helos another individual with expepectation that it will be retrurned
kin recognition
abillity to recognize and identify close relatives
closely related
direct and indirect
Can kin selection occur without kin recognition?
yes
direct kin recognition
based on a specific chemical vocal or other cues
indirect kin recognition
like a location of a nest
think about the cuckoo bird video from lecture
parent offsrping conflict
conflict may occur when parents an offspring disagree abt. fitness interests
types: weaning conflict and sibicide
what conditions can reciprocal altruism evolve
- benefit to the recipient of act is greater than cost to the actor
- capable of recognizing each otther
- repeated interaction between individuals
weaning conflict
disagreements between parents and offspring abt the amt and duration of parental provisioning
each offspring will demand more investment, where parents want to give equal investment
siblicide
extreme sibling rivalry where they will attack and kill each other in different occasions
found in masked and blue footed booby
eusociality
extreme form of altruism
nonreproducive individuals participate in the cooperative care of young
ants, bees etc
overlapping gens. between parents and offspring
cooperative brood care
specialized group of non repoductive individuals