Evolution After Midterm 1 Flashcards
What are qualitative traits?
Discrete phenotypes ; can assign individuals to categories with ease
What are quantitative traits?
- indiscrete, measurable phenotypes; cannot using with ease, varying intensities
Is most biological variation quantitative or qualitative? Can we use HW models?
- most variation is quantitative, must be measured
- most traits are also multi locus (>2) - so we cannot use HW / Mendelian ratios
What are mendelian ratios initially for? Can they be used to explain range of phenotypes in organisms?
measure qualitative and discrete traits passed on in mendelian ratios -
- but Mendel’s model of inheritance can also be used to explain range of phenotypes observed (still sorts independently)
Why do we need quantitative genetics?
- we need it to study multi locus traits
- most ecological relevant traits are multi locus, too complicated for HW models
provides tools for: predicting response to selection, measuring differences in survival/reproduction, measuring heritable variation
What traits must phenotypic variation have that allows populations to evolve?
- must be heritable allowing for differential reproductive success
What are the traits we observe in determining heritable variation?
- determine how much of a trait is due to environmental and genetic variation
- determine genetic contribution
What is heritability?
the fraction of total variation in a trait that is due to variation in genes
What is broad sense heritability (H^2)?
- for population
- ratio of the total genetic variance to total phenotypic variance
- includes all genetic contributions to a population’s phenotypic variation
for an individual : P = G + E
total variation: Vp = Vg + Ve
What is the equation for broad sense heritability?
H^2 = VG/VE = VG/(VE+VG)
What is narrow sense heritability?
ratio of additive genetic variance to total phenotypic variance : in individuals (how much parent passes on to offspring)
- describes extent to which offspring resembles parent
What does h^2 allow us to predict?
- allows us to predict how a population will respond to selection because it describes the extent to which offspring resemble their parents
What does an h^2 value of 0, 0.5, 1 indicate?
0 means that all variation is due to the environment, 0.5 means there is some genetic and environmental component, 1 means variation is entirely due to variation in genes
What is the equation for narrow sense heritability?
H^2 = Va / Vp = Va / VA + VD + VE
What is additive vs dominant genetic variance?
- VG = VA + VD
- additive is the variation due to additive effects of alleles/loci (co-dominance ; how much it ‘adds’ since they are combined and express new combined traits)
- Dominant is the variation due to gene interactions like dominant alleles
- if some dominance, VA reduced
What does it mean when all genes act additively?
VG = VA
will narrow sense heritability change if we switch environments?
yes!
- look at eq- it will change as environment or allele frequencies change
What are the 3 methods of determining whether traits are determined by genes or the environment?
- GWAS (Genome wide association studies)
- QTL (quantitative trait loci)
- Common garden experiments
What are GWAS?
- genome wide association studies looks for association between loci and phenotypes
- sequence many individuals, find SNPs (Single nucleotide polymotphisms) - look for association of SNPs with phenotype of interest
- confirm with other populations
What is QTL mapping?
- quantitative trait loci - portions of the genome that influences quantitative traits
- QTLs are mapped by identifying which molecular markers correlate with an observed trait
- do not actually identity which genome but just stresses of DNA linked to the causal gene
What are common garden experiments?
- test for environmental effects by growing species outside of their usual environment
- don’t usually know the genes just that they differ - can detmeurine H or h ^2
What does variation within a common garden experiment indicate?
No VE< only VG
Can heritability within populations describe the causes of the differences?
heritability within populations tells us nothing about the causes of differences between population means in different environments - changes in environments causes changes not genes
Why is heritability often misinterpreted?
- assumes that differences between populations are due to differences in genes
- not the case, must consider environment
Describe the example of IQ in humans
IQ in humans, h^2 = 0.6 indicates some heritability
- so we can assume that there is a genetic component in differences in populations
BUT this does not imply that IQ differences between populations are due to genetics, the groups have different environments
- phenotypic differences but no genetic differences
to test this we would need to compare both values in different environments:if genetic, should show difference, if environmental should show same curve (not ethical / confounding factors in people)
Can genotypes respond differently to different environments?
YES species may be locally adapted, gentoypes can respond differently to different environments
What are adaptations?
Inherited traits that make an individual better suited to their environment: increases their fitness
- must evolve via natural selection and serve the same trait as it did when it was developed
How can we prove that a trait is an adaptation?
1) determine the function of the trait
2) prove that individuals without that trait have a decreased fitness compared to those with the trait
Explain the ox and red billed oxpecker example
- initially thought to be mutualistic
- experimentation revealed that ox tried to shoo them away, they collected earwax, harvested dead skin and ate blood
- parasite load (ticks) did not change, but earwax decreased and open wounds increased
- conclusion: birds are a blood parasite
(does not define all interactions between oxpeckers and large mammals - eg; birds on the rhino help them =mutualist) - nature is complicated
- oxpecker adapted for blood collection not parasite removal
What are some key points on adaptive studies proven by the ox and oxpecker?
- adaptations are not as obvious as they appear
- plausible hypotheses are the beginning of experimentation not the end
- all hypotheses must be tested!
What are the main approaches for studying adaptation?
- controlled experimentation
- observational research
- comparative method
Describe controlled experiments. what factors make for a good experiment?
- this is where one trait is changed, ideally all other traits are identical and the one independent trait is altered to see how it impacts other dependant factors - differences in survival and reproduction should be due to that trait!
factors:
- question phrases as precisely as possible
- all alternative hypothesis and predictions defined (really good ones will test these as well)
- a way to manipulate the independent variable
- a way to measure the dependant variable changes
- randomization, replication, adequate controls
eg; Oldfield mice
Define observational research?
- when a trait is not easily experimented on: careful observation could provide answers instead
- ## eg; Darwin and huxley proposed that humans related to great apes: used comparative anatomy + molecular genetics supports hypotheses (1.3% difference, differences may be due to different gene expression)
Define comparative methods
- observing traits among multiple taxa of populations
- looking for trends in evolutionary history - look for similar traits/functions and if they are very common in multiple species may be an adaptive function
What is the problem with comparative methods?
- some species may have evolutionary history: similarities may be due to relationship and not evolution
- correlations may not be statistically significant
What are the phylogenetic comparative methods?
- 1) PICs : phylogenetic independant correlation
2) phylogenetic generalized least squares
3) logistic regression
Describe the steps to PICs?
1) obtain phylogenic tree of interest
2) find ancestral trait values (averaging descendants)
3) identity sister pairs (taxa-use branch once)
4) calculate contrasts for each pair!
5 ) calculate regression / correlation and determine if relationships are significant
What is required to determine if x and y are co evolving?
- phylogeny
- measurements of 2 traits
Describe PICs?
- to determine if there are correlations between traits we need to evaluate the taxa but ancestral history may make correlation statistically significant
- PICs evaluates the correlations while taking into account evolutionary history
- looks at patterns of divergence as sister species evolve independently from common ancestor: looks at divergence from ancestor
- if contrasts are significant we can conclude that traits are related : because they are related cross all taxa, so as they diverge they change together meaning they are related
- we would expect to see correlation between traits of all taxa because they are correlated
What are some challenges with studying adaptations?
- phenotypic plasticity: genes can undergo evolution: may change in response to environment
- tradeoffs/constraints: trait could reflect a compromise between conception environmental or physiological demands or reflect physical constraints
- selection can act at multiple levels
What does it mean that selection can act at multiple levels?
- selection is the differential survivial/reproductive success of some entity (entities range form nucleotides to genes to cells to individuals to population etc)
Define selection acting at multiple levels:
- at the individual level in a population: variation: different colours
- differential erprodutive success: selective agents remove certain less fit ones
- inheritance: only those remaining (brown beetles) breed and have more brown beetles
- at the cellular level within an individual:
variation: mutations in cells produce more
differential birth and death: mutated cells have more offspring
inheritance: mutation offspring inherited mutated DNA, normal inherit normal DNA
At the species level:
- variation: certain species experience patchy disruption, others don’t
- selection/ differential birth and death: patchy distribution more likely to undergo speciation
- inheritance: patchy species give rise to species with patchy distribution, normal distribution give rise to species with normal distribution
Which levels have the most power for defining whether a trait is adaptive or not?
which have the least?
most: genes and individuals
- Traits directly affect an individual’s fitness, providing clear evidence of adaptiveness. (compare one individual to another can see which is better)
- genes provide direct evidence of evolutionary changes under selection.
Can identify specific mutations or alleles responsible for adaptive traits.
least: species and populations
- Comparative analyses across species can suggest adaptiveness but often rely on correlations rather than direct tests of fitness. - harder to determine if it is a result of adaptation or historical relatedness
-Patterns of trait variation across populations might reflect genetic drift, neutral evolution, or historical constraints rather than adaptation
can selection act simultaneously?
yes at multiple levels
What is sexual selection?
- natural selection works on not just traits that improve survival but also those that improve their ability to convince the opposite sex to mate
- differential reproductive success due to individual variation in mating success
- ie: selection for traits and behaviour that improves mating success
How does evolution via sexual selection occur?
–> organisms with heritable traits favouring mating success have more mating opportunities –> increase in frequency in future
Does NS always support sexual selection?
- no sexual selection can be opposed by NS (may not increase fitness or survival but increases reproduction!)
does sexual selection work in different sexes?
- sexual selection works differently in males and females- leads to sexual dimorphism
What is sexual dimorphism? How may it have arose?
- sexual selection acts on males and females differently ; males and females differ morphologically inducing traits not directly involved in reproduction
–> different parts of selecitondue large in part to anisogamy: greater than 2 different kinds and sizes of gametes produced
What is anisogamy?
- reproductive system in which greater than 2 types and sizes of gametes are produced eg; sperm v egg
how did anisogamy come to be?
- where smaller sperm are more mobile, and larger sperm are fewer but larger
- zygote survival increases with size which depends on gamete size
so - selection should favour fusion of protosperm (smaller) and protoeggs (more biomass) (fusion of protoeggs but larger gamete rate)
- disruptive selection = small sperm, large eggs!
What are the two predictions regarding sexual reproduction leading to sexual selection? (gamete size) What do these lead to?
- males should compete for mating opportunities
- females should be choosey
since eggs are large and scare, highly valuable compared to sperm so
- leads to different behaviour, morphology, physiology between sexes
why might males be expected to compete for more mating opportunities?
- lots of variation in male reproductive success: some low some high due to large mass of sperm , females more intermediate reproductive success
Why should females be choosey ?
- eggs are costly and rare, females stand to lose more if they choose the wrong mate:
- especially true for internal gestation: must put energy before offspring are born so must be good investment
Why does selection act differently on males and females?
because of anisogamy!
(more sperm; compete, more variation; fewer large eggs, get to be choosey of males for payoff with rare egg) = under different selective pressures
What are the two forms of sexual selection ?
Intrasexual selection : completion between members of the same sex competing for opposite sex Imore common in males)
- intersexual selection: one sex selects opposite member (typically female chooses male)
what are the 4 mechanisms of intersexual selection?
- 4 evolutionary models:
- direct benefit
- good genes (and costly traits)
- fisher sexual selection
- sensory bias
Describe the direct benefit
- females prefer males who can bring more resources that benefit fecundity or growth ; fly selects male that brings more benefit, and male gets to mate with female
- 2) protection from predators
- mate guarding: males who stay with female before and after copulation benefit: males can prevent other males from mating and protect from predators
- female gets protection from predators
- eg; amphipods; larger ones get more success because of higher survival
Describe the context for the good gene hypothesis
- not all sperm will be equally good last producing offspring - selection fairs females who will choose males with good genes; genes that code for favourable traits
How do females select for the good genes if males can lie?
- expect only traits that are honestly indicative fo quality are selected upon by the female
What is the purpose of ornaments in the good gene hypothesis?
- ornaments can serve as honest indicators of genetic quality based on the handicap principle: only healthiest males can afford to produce and maintain ornaments, less costly for healthier males to produce therefore a good honest indicator
What is the propose of the handicap ornament?
When a trait is a handicap it can serve as an honest single of genetic quality
Describe the fisherian sexual hypothesis?
- some females express a preference for a males trait - if trait and preference are genetic can become linked and increase in frequency - offspring carry both traits
- sexy son mechanism: female mating with who she prefers is reinforcing; leads to offspring having higher reproductive success
How does fisherian sexual selection and NS work together?
- generally there is a balance between the two
What occurs when the association between preference and trait is very high?
- can lead to runaway sexual selection: produces increasingly exaggerated traits in a feedback loop if there is no associated cost
How can we determine the difference between fisher sexual selection and good gene hypothesis?
- good gene hypothesis is an ornament associated with quality
- FSS is preference on top of good genes - ornaments indicate sulky and preference - good genes mechanism strengthens selection
What is the sensory bias model?
- a preexisitn bias in the sensory system of one sex favours member son the opposite sex who display the same trait
- triggered by excitement in element of nervous system or preference due to benefit outside of mate selection
eg; female likes red berries, males develop red wings randomly, female prefers red wing male due to pre exiting trait
In the sensory bias model, does the female inherit the trait preference after the male does?
No! The preference is likely pre-existing
Are intersexual selection models exclusive?
NO! many mechanisms can occur at once
- evolution of. asexual trait could be explained by more than one of these models
What are the forms of combat in intersexual selection?
- cuckoldry, combat, sperm competition,
Cuckoldry?
- male unknowingly cares for young that are not his own
eg; bluegills; sneakers and satellite may get sperm in female that parental then takes care of because he thinks they are his
Sperm competition in bluegills?
Snakers producer low quality short living lots of spemr, while parental produce fewer high quality sperm
What is sperm selection?
- sexual selection acts not only on male behaviour and external morphology but also on sperm’s ability to reach and fertilize eggs
What is postcopulatory sexual selection?
- sexual selection occurring after mating has taken place ( sperm completion)
What is sexual conflict? What can it lead to ?
- because selection can act differently on males and females in terms of mating, they may have traits that are detrimental to the other sex
- can lead to antagonistic coevolution
What is antagonistic coevolution?
- an arms race between males and females
eg; in drosophila seminal fluid- seminal fluid actually decreases longevity of females- it develops a sperm plug and makes her less receptive to other males, and triggers egg production and laying BUT that is costly, reduces survival chances and chances of mating again = antagonistic , the want to mate harms female
What is extinction?
all individuals of a species have died out and left no living descendants
What is a fossil?
- remains or traces of a once living organism
What is fossilization? How does it occur?
- organic material being preserved over time
- very gradual process
- more time = more rock like
- calcium and phosphate are replaced over time by iron and silicate
- sometimes can be preserved in amber
- carbonization also occurs
What is carbonization?
- thin layer of carbon preserved on sandstone or shale
What is the best place to find fossils?
fossil tend to form in sedimentary rock: sand, chalk, shale, sandstone,
What is dissolution?
- when water breaks down fossil and only the outline remains
What is the fossil record?
history of life on earth based on fossil remains: reveals what the earth was like at the time of their existence
What is the law of superposition?
- a way to date fossils based on depth in the soil: ie: deeper= older
- relative age
how do you measure relative and absolute age of fossils?
relative age: law of superposition
Absolute age: radiometric dating (measuring half life, check ratios and / or surrounding sediment)
What is the signor lipps effect?
the gap between the last discovered fossil and the actual date one extinction
- backwards smearing: dating extinction earlier than it occurred
- forward smearing: dating extinction later than it occurred (happens from burrowing animals, can offset risk of error by checking for evidence of burrowing around fossil)
What is a mass extinction?
- series of events that uses large scale loss over broad geographic range - in a relatively short amount of time
- no clear definition but argued that> 75% species loss
How many mass extinction events have occurred? What are they called?
- 5 mass extinctions known to occur within the last 600 million years
- end of ordocivian, late Devonian, late permian, end of triassic, KPg (cretaceous paleogenic boundary)
How do we study ongoing and past extinctions?
ongoing: look for last living representatives
past: search for fossils
Are all extinctions equal?
- no! Loss of larger branch is worse- loses all of the evolutionary history
What are background extinctions?
Extinctions occurring between mass extinctions: 95% of species extinction have been background extinctions
What are some causes of background extinctions?
- predation: predators adapted to become more efficient (prey too) - eg; clams have larger dents before they go extinct indicates that predators became better adapted and wiped the population out
- introduction of new species, overhunting, indirect effects (human intervention)
- disease: can wipe out populations quickly: global decline in amphibians 7/14 gone extinct since 70s = disease takes them out within a few months
- competition: certain species can become better adapted and out compete others with the same niche
Is each method of background extinction exclusive?
- no! They are not mutually exclusive - can occur together eg; extinction of endemic Hawaiian birds caused by two waves of human colonization - introduced disease, predation (hunting for food/feathers), introduced non-native species and habitat destruction
What is an endemic species?
- a species native to the area- many examples of extinctions are from endemic species because local extinction = global extinction
What is a dead clade walking?
A species that survive the extinction event but die in the years following (due to ecological changes associated with the loss of so many species and environmental changes)
That is phyletic gradualism ?
- new specie arise when ancestral species undergoing constant, slow changes
- enough change leads to new species
What is punctuated equilibrium?
When evolutionary hang occurs in a lineage it is rapid and often leads to branching speciation (cladogenesis)
- apart from branching event lineage in stasis (unchanging)
What is cladogenesis?
- modification of form associated with branching speciation
- associated with phyletic gradualism
What is anagenesis?
- gradual modification of form over time
What type of modification do horse lineages describe?
- represent both : undergo branching speciation (cladogenesis) but those branches undergo gradual change as well (anagenesis)
What is pseudoextinction?
When ancestral species goes extinct due to anagenesis event
- pseudo because lineage has not died out, but previous species has
How are the fossil record and rates of evolutionary change related?
- rates of evolution can be interpreted from the fossil record which can link extinction to understandings of speciation
What is de-extinction? What are some issues associated with de-extinction processes?
- using advancements in ancient DNA to bring formerly extinct species back using modern DNA technology
- is it ethical? and fragmented DNA and developmental conditions may also prove to be problematic
What is coevolution?
the process in which changes to heritable traits in one species drivers changes in another species (they impact each other)
What are the two broad categories of coevolution?
- mutualism : interactions between two species increases fitness of both
and antagonistic coevolution : interactions decrease fitness of the species
What are the two forms of co-evolution?
- pairwise co-evolition: originates between just two species
- diffuse co-evolution: multiple species (more than 3) impact each other (can include both mutualistic and antagonistic relationships )
What is an example of diffuse coevolution?
- ants, grass, fungus, and bacteria - mutualism and antagonistic relationships both involved
What are the selecting traits for coevolution? Biotic or abiotic?
can be biotic or abiotic
- responses to abiotic conditions will not change abiotic conditions
- response to biotic conditions may influence other species
What is escape and radiate co-evolution?
- ## process where novel traits favored by one species could provide opportunity to colonize new areas
How does mutualism evolve?
- can evolve from an earlier form of mutualism, neutralism, commensalism, even parasitism
- where interactions increase fitness of all species involved
- no one set way in which mutualism can develop
What are the two forms of mutualism?
- obligate and facultative
Describe mutualism and communication
- if mutualism is costly, but with net benefits, NS tends to factor communication methods
- NS will favour communication if it increases fitness
Describe mutualism and cheaters
- cooperation provides incentives to cheat and reap benefits without the cost
- NS selects fora ability to ‘punish’ cheaters which stabilizes mutualism (cheating does not spread or persist)
What is cospeciation? How might it arise?
- individuals that are undergoing stable mutualism for a long time may develop co-speciation: where speciation of one species leads to speciation of the other
- may arise from allopatric mechanisms or differences in niches
- reciprocal reliance within mutualisms may lead to development of cospeciation (increases diveristy)
What is antagonistic evolution? What are the two forms considered?
- antagonistic convolution: when interactions between two specie decrease fitness of the species - changes impact each other
- look at it from a predator prey, and a host parasite perspective
Describe the predator prey antagonistic relationship?
- evolutionary arms race: selection in one species drives selection on the other species
-NS favours increased prey adaptations, and in return the predator adapts, and prey adapts, etc… - bivalves and whelks
Describe the host predator antagonistic coevolution relationship?
- divergence between host species populations often leads to divergence in parasite populations
phylogenic of hosts and parasites often observed to change in parallel
- cospeciation common
- when the host population becomes isolated from one another, often produces geographic isolation for the parasite as well
What is mosaic co-evolution?
- a situation where two species interact differently in different environments (mutualistically in some, antagonistically in others)
- leads to geographic variation in co-evolutionary outcomes
give an example of mosaic co-evolution
- woodland star and moths
- moths lay eggs in plants, and pollinate
- in areas where there are no other pollinators: mutualism
- in areas where there are other pollinators moths are expelled at no cost: antagonistic relationship
- geographic variation in co-evolutionary outcome
What factors are considered in determining which type of interactions (mutualism or antagonism) NS will favour?
- the cost and benefit of the relationship
- coevolution occurs in each community but what kind depends on costs and benefits of the interactions
How does culture influence evolution?
cultural evolution can affect genetic evolution
What is cultural transmission?
- the transfer of information from individual to individual through social learning
- information can spread rapidly
- behaviour of one individual can alter the behaviour of an entire population
- changes frequency of behavioural traits within and across generation = cultural evolution
Describe homo floriensis
- discovere don an island, extinct 60 k years ago
- likely derived from h. Erectus prior to h. sapiens diverged
- used fire, tools, hunted
- flat face and soul geometry confirms they were in homo spp. but similar to arhacic as well - unclear where they fit in the phylogeny
- short (~1 m) due to insular dwarfing + large flat feet and walked upright
Describe homo heidelbergensis
- 500 - 800,000 years ago
- may be direct ancestor of Homo sapiens
- mode 1 tools, eventually evleopoed mode 2 tools
- hunted larger game
Describe homo neledi and homo luzonensis
- Homo naledi: homo characteristic but also many archaic characteristics - walked upright, 1.5 m tall
- possibly buried their dead
Homo luzonensis: small, placement uncertain, some bones, 134,000 ya
what is the cooking hypothesis?
- h. Erectus used fire (there is evidence in caves etc)
- but it may have been used earlier than that
cooking hypothesis: morphological changes may have been due to the increased nutrients driven from cooking food - change in dentition: reduced jaw, molars, digestive tract - increased brain size required more energy = difficult to meet with raw food
What are the two models of evolution of modern humans?
- multiregional hypothesis : all humans moved out of Africa at once, diverged from there - was enough gene flow that speciation did not occur
- out of Africa hypothesis: 3 waves homo Erectus, heidelbergensis, sapiens
- premodern hominids were replaced by humans
What is some evidence of the out fo Africa hypothesis?
- tool making evidence
- fossil evidence : gradual anatomical divergence
- mitochondrial DNA: greater genetic variation. within Africa (founder effect, traced women’s DNA back to mitochondrial eve)
What did homo heidelbergensis give rise to?
- split into Denisovans and Neanderthals (human sister taxa) - coexisted with homo sapiens
- neanderthals: larger, stronger, brow ridge - speech, mode 3 tools, hunted, cared for sick, and dead
- Denisovans: genetic evidence only (finger bone, some teeth)
- Homo sapiens appeared - upper paleolithic lifestyle
Did Homo sapiens and neanderthals interbreed? What evidence is there
share allele - suggests inbreeding or deep coalescence
- if interbreeding; europeans should have more genetic commonalities than africans (1-4%)
Did Homo sapiens intercede with Denisovans?
- people of tibet have high altitude tolerance similar to Denisovans - suggests interbreeding
What conclusions can be drawn from anisogamy?
Because female gametes are valuable and rare while males have many small ones competing :
1) males should be competing: leads to different morphology, behaviour, and physiology
2) females should be choosy.
What is the sexy son mechanism?
- genes for preference and the trait become linked
- female preference is self-reenforcing - by mating with brighter males offspring will be better mating prospects
What are genes ?
Segments of DNA that code for specific products (forms proteins)
What are the functions of proteins?
- intracellular communication, enzymes: regulate and initiate chemical reactions, transportation, forms parts of ECM and cytoskeleton, regulates DNA expessoikn
What are regulatory elements?
- stretches of DNA that alter the rate of transcription and therefore gene expression
- also transcription is heavily impacted by chromatin structure: wound too tightly leads to blocked access to promoter region
What is cell differentiation?
- methylation and histone modification alter gene expression in different cell lines
Describe the mechanisms of epigenetic inheritance across cell generation?
- cell differentiation
- x chromosome inactivation
What is developmental plasticity?
- phenotypic adaptations to environment in utero ( ie: mother’s diet increases risk of metabolic disease later in life)_
What is cell differentiation?
- mechanisms like methylation and histone modification alter gene expression in different cell lines
Describe mutations. What kinds of mutations are there?
- heritable mutations occur in the germ cell lining
- changes to the DNA sequence of an organism
- can be deleterious, natural, or beneficial
- can alter phenotype if it alter the expression/function of proteins
- mutations include: points mutations: substitutions, insertions and deletions, gene duplication, chromosomal rearrangement, genome duplication, recombination
What are point mutations?
- aka: substitutions
- transition and transversions
- can be synonymous, non synonymous, or nonsense (STOP codon generated)
What are insertions/deletions?
- another form of mutations
- in-frame mutation: multiples of 3
- frame shift-mutation: non multiples of 3
What is gene duplication?
Mutation where a region of genes or entire gene is duplicated
What is chromosomal rearrangement?
- mutation where chromosomes are rearranged
- translocation (one end moves to the end of another chromosome)
- inversion (flips 180 degrees)
Aldo includes chromosomal duplication and chromosomal deletion
What is genome duplication?
- entire genome is added or removed, change in ploidy
-usually fatal in animals because meiosis cannot proceed
What is recombination?
- occurs in sexually reproducing organisms
- during meiosis, chromosomes cross over and form new combinations of alleles not seen in parents
- can unlink linked loci, or reduce mutations (benefit of sexually reproducing organisms - can reverse muller’s ratchet)
How do mutations and NS work together?
- mutations introduce variation into the population
-mutations and NS work together to maintain or increase the mean fitness of a population
If mutations are generally deleterious or neutral, shouldn’t genetic quality be decreasing over time?
- NS selects of beneficial alleles and removes deleterious ones, allows genetic quality to be maintained
If a locus is at hardy Weinberg equilibrium, can we say that the population will remain at equilibrium?
NO! We cannot say they will remain at equiblirum, and only that locus is at HW equilibrium , others could be evolving
What occurs in frequency independent over dominance?
- balanced polymorphism
does mutation work quickly on it’s own?
this is genetic drift- random allele frequencies - no much slower
What are some consequences of assortative mating?
- inbreeding increases homozygosity, reduces vairiaotn
- can lead to inbreeding depression: decreased fitness associated with inbreeding,
- eg; wolf cub survival has a negative relationship with inbreeding coefficient
What makes migration a homogenizing process?
- makes populations more similar
What is the main cause of inbreeding depressions
overdominance: heterozygotic advantage (since inbreeding increase homozygotes)
but more commonly:
rare, recessive, deleterious alleles
What are 3 main consequences of genetic drift?
1) in a finite population allele frequencies fluctuate in absence of NS
2) can increase, decrease alleles and cause decrease of heterozygotes (genetic drift decreases heterozygotes, promotes homozygotes)
3) causes divergence of separate populations - drift is random so in different population will behave differently
Why might mutations be natural with respect to each other?
- non coding region: pseudogenes: non functional region of DNA, accumulates mutations rapidly
- synonymous mutations: synonymous mutatiosn DO create molecular variation but are neutral with epsoect to fitness (because they do not alter the expression)
- nonsynyomous mutations: not completely natural, but the further from binding site the les impact they have
How do pseudogenes arise?
- come about from gene duplication events, or gene deactivation (not selected for enough)
Why are non-synonymous mutations a plausible lesion for neutrality in the neutral theory?
- not neutral because it does change protein structure and function, HOWEVER the further it is from the binding site the lower the impact on fitness
Why is linkage disequeilbirum important?
- selection at once locus can impact selection at another locus
- combination of alleles can be favoured
Why do we care about linkage disequilibrium?
- to determine whether fluencies at locus A will interfere with the ability to predict B frequencies
Can we use hardy Weinberg to study linakge disequilibrium?
no - only linkage aequilbirum which are idnpenedant
- in disequilibrium genetic hitchhiking and them being inherited together makes HW inaccurate
Why do we need quantitative genetics?
to study multi locus traits: traits with no discrete measurement, variable,
Which form of selection increases variation? Which decrease variation In phenotypes?
- disruptive selection allows for broader variation
- stabilsign reduces phenotypic variation
if stabilizing and directional selection are occurring, how is genetic variation maintained in populations?
1) lack of equilibrium: beneficial mutations have not yet reached 100% fixation
2) mutation-selection balance: selection removes deleterious mutations, and introduces variation into population
3) other forms of selection may be involved too: disruptive selection may be more common than expected, frequent dependant selection, selection imposed by fluctuating environments (as environment changes so does selection -changes)
What is the correlated evolution of traits?
- when selection on one trait causes evolutionary response in another trait
- when this occurs called: genetic correlation between traits
What are the mechanisms of genetic correlation between traits?
arisen by
- linkage disequilibrium: linked loci that are inherited more often than random
-pleiotropy: selection on one locus impacts other seemingly unrelated phenotypes
What is pleiotropy? Provide an example?
- a mechanism for genetic correlation between traits
- when selection at once locus impacts other seemingly unrelated phenotypes
- eg; frizzle chicken: deletion in code for keratin makes feathers not lay flat but also impacts heart rate, delayed sexual maturity and increase metabolism
What are comparative methods?
Looking for trends in evolutionary history by comparing traits in multiple species
- similar trait functions across multiple species is good evidence that that trait is an adaption
What is the handicap principle?
- only the healthiest males can afford the largest ornament
- a costly trait ensures honesty
- when a trait is costly it serves as an honest signal
How do females assess gene quality?
we generally only expect females to assess traits that are costly and an honest indicator of quality y
When are conventional signals vs. costly signals uses?
- conventional signals (which aer enforced through social conventions) are used when there is a way to verify their honesty
- costly signals used when there is not way to ensure honesty (eg; baby birds use costly signals for food to demonstrate that they are not lying dn need food, cannot check otherwise )
Why should females be choosey?
- eggs are rare, and costly to maintain offspring - must choose good quality males and make the cost worth it
How do FSS and good genes hypothesis differ?
- FSS works on top of good genes hypothesis - assesses quality and preference (preference for a greater quality may become linked)
- GGH- assesses quality based on ornament
Which model addresses the origin (not the mechanism) of preference?
- sensory bias model
Describe the evolutionary species concept?
- defines what a species is
- species must have distinct shared evolutionary history and a distinct shared evolutionary future
What are the species concepts used for?
- species concepts define how to delineate populations, while the evolutionary species concept defines what a species is
Define the phenetic species concept?
- defines species based on morphological characteristics
- defined as a morphospecies
- used for plants, aexual reproducers (microorganisms), and extinct species
- also used for higher taxa: genus, family, orders, etc
- common approach by numerical taxonomists
What is the challenge associated with the phenetic species concept ?
- computational algorithms used to determine traits do not identify what may be convergent evolution- only assesses traits - does not make any assumptions about cause of clustering
- but species may have undergone convergent evolution and not be related at all
- and: are all characters equally important in establishing evolutionary history? - probably not
Define the biological species concept
- defines species based on their ability to actually or potentially interbreed and produce viable fertile offspring ; reproductively isolated
- mechanism of evolution: gene flow
- challenges: in partially viable hybrids how do you define? - how low quality does offspring need to be, and how frequently does interbreeding need to occur to be defined as separate species ?
What is the ecological species concept?
- defines species based on their niches - differ species = different niches = different competition levels
- but how does one define a niche? = different abiotic and biotic components
- species with different lineages will have different adaptation to different niches (different habitat, food, reproductive timing, etc)
Under the biological species concept, is a group of individuals who look like cats considered a species?
not necessarily - if they are interbreeding yes, but does not define species based on phenotypes but gene flow
what is the phylogenetic species concept ?
- identify species as the smallest monopyheltic group distinguished by a shared derived character
- used on traits (phenetic) AND evolutionary history
- characters must be absent form all other groups on the phylogeny
-smallest monophyletic group provides appropriate levels to draw boundaries (eg; mammary glands and fur is too broad, applies to all mammals but. less fur and speech is small enough to define humans)
Can polyphyletic characters be used in the phylogenetic species concept?
no they’re too variable
What is the challenges with the phylogenetic species concept?
- there is no reuqrirment for reorducive isolation : violates evolutionary species concept (distinct shared evolutionary hiostruy - not true if species are separate and then can breed again)
- often species are divided into too many species inappropriate relative to other species concepts
How is the phylogenetic species concept and the phonetic species concept similar?
phylogenetic defines species based on morphological traits (like phenetic) BUT it also considers evolutionary history of these characteristics
What are the two models of allopatric speciation ?
- vicariance (2 large) and peripheral isolate model ( 1 big, many small)
What is speciation?
- occurs when reproductive isolating mechanisms evolve between isolated populations (via NS or drift)
- when gene flow stops they are consider two separate species
What is true of all speciation models?
they all include divergence of populations ( reproductively isolating mechanisms)
After speciation occurs, what prevents interbreeding and gene flow?
NS and genetic drift encourage reproductive isolation mechanisms
What is parapratirc speciation?
- neighbouring populations, interbreeding occurs however hybrid zone often not selectively favoured because they are neither adapted to either environment - sometimes if the hybrid is better adapted to hybrid zone then either parent they will undergo speciation and form a 3rd species
- most often however they are selected against and populations complete speciation n
When does hybridization and hybrid zones stop?
- when the parent populations are fully separated, speciation is complete ; reproductively isolating mechanisms
What is sympatric speciation?
No geographic isolation: geography is not the only mechanism of speciation
How does speciation occur if there is no geographic barrier?
- there are many reproductive isolating mechanisms
- resource competition, spatial dsitrubtion, temporal isolation (reproductive isolating mechanisms)
What are the two forms of reproductive isolating mechanisms?
post zygotic and pre zygotic isolating mechanisms
- post zygotic; after fertilization, makes F1, F2 inviable or ends zygote
- pre zygotic: behavioural, temporal, mechanical, gametic incompatibility, habitat isolation
How do the biological species concept and the phylogenetic species concept differ on their classifications of the coil shell snails?
- biological species concept defines as 2 species because they are reproductively isolated
- phylogenetic species concept argues it’s one because they have same traits and evolutionary history
How might sexual selection act as a reproductive isolating mechanism?
- assortative mating: mating behaviour can promote speciation
How might a change in ploidy (genome duplication) result in reproductive isolation?
- often results in death because meiosis cannot occur BUT if it does it leads to instant speciation - can only breed with others of the same condition (if they exist)
What occurs if individuals of different policy levels interbreed?
if they manage to produce a viable offspring it will likely be infertile
What is the difference between autopolyploidy and allopolyploidy
- autopolyploidy: single parental species - may have viable offspring if self feritlsie or mate with another polyploid
- allopolyploidy: 2 parental species
What conditions do speciation via changes in policy require?
- tolerance to drastic chromsome changes
- waiting between individuals of the same chromosome number
Is polyploidy common in plants and animals?
- more common in plants; have good tolerance to increase in chromosome numbers, and can self fertilize
- less common in animals but can occur (eg; frogs)
What is the Dobzhansky - muller incompatibility hypothesis?
- epistatic interactions between polymorphisms that have developed
- two species may get new allele and diverge - then when they try to breed negative epistatic interactions between the two new alleles have severe fitness cost and induces speciation due to factoring reproductive isolating mechanisms
What is Haldane’s rule?
- in hybrid offspring is a sex is rare, absent, or infertile it is likely the heterozygote because the homozygote can mask if it is recessive deleterious , but if it is in male. XY cannot be masked
What might competition between groups favour?
- cooperation between groups (ie: alarm calling group may have better success)
NS is said to operate at two levels, what are these levels? c
In group selection - acts against free rides - and between group selection - acts against non-cooperating groups -
What process helps stabilise mutualism
- the ability to punish cheaters ensures that free riding does not increase or spread
What might lead to cospecaition?
the reciprocal reliance within mutualism may lead to cospeciaiton and increase bidovieisry
How might mutualism increase biodiversity?
- in co-speciation ; when reciprocal reliance associated with mutualism causes cospeciation will increase diversity
What is gene culture coevolution? Provide an example?
When traits associated with cultural transmission leads to genetic evolution
eg; humans used to not be able to have lactose then cultivation of cows and dairy occurred - can now digest milk
cultural evolution impacts genetic evolution
What are the two ways of transferring information between generations?
- genes are one way, cultural transmissions is the other way
Why might cooperation develop when it can be costly to individuals involved?
- altruism (kin selection) and free riders are punished - benefit can be gained form cooperation that poses risk for reasons of kin selection, reciprocity, and group selection!
Can sociality be costly?
it can have a cost but the benefits outright the costs
- NOTE : communication may be favoured by NS if there are costs that are outweighed by the benefits
what is sociality?
the degree to which organisms form a social group and cooperative society - if living together they may as well cooperate - can have a. cost but outweighed by benefit
What characterizes eusociality?
- cooperative raising of young, overlapping generations, reproductive and non-reproductive castes
What factors does sociality depend on?
exchange of communication and information
How does communication in sociality evolve?
0 if interests of both coincide no reason not to share information = honest signalling
What is honest signalling?
- when the intents of the receiver and the giver align, no reason to not tell truth
When might signalling be dishonest?
- when the intents of the receiver and the provider do not align
- eg; mind reading and manipulation
how is honesty in signalling ensured?
- mind reading vs. manipulation: not ensured
- conventional reinforcement of honest signalling
- costly signals :if costly honest signals are favored (handicap principle)
Describe mind reading and manipulation?
- if interests of the communicators do not align, this may lead to dishonest signalling from antagonistic convolution
- mind-reading - idnivuaslm try to gain edge by observing cues
- manipulation: portaying cezain signals
Are dishonest signals expected to be maintained?
No! signals expected to change over time as arms race continues - adapt to each other
What are conventional signals ?
- meaning is established by convention rather than related to structure (Cost)
- what keeps signals honest = social reinforcement
Why use a costly vs. conventional signal?
Describe the timeline of homo heidelbergensis giving rise to neanderthals and densiovans?
- heidelbergensis gave rise to neanderthals and densiovans around 600 kya,
- gave rise to them out of Africa around 200,000 ya, and they persisted until 30,000 years ago
-humans 40-50 kya lived an upper paleolithic lifestyle
Why are homo florisensis and neredi similar to archaic homiims? What makes them similar to homo?
- they both had small brains similar to that of archaic homonims
- floriensis had similar skull morphology and a flat face that indicates homo species
- neledi had many homo characteristics: reduce jaw and molar, cranial structure, feet adapted for walking ,
when did homo. heidelbergensis give rise to homo sapiens?
Homo sapiens around around 130-200 kya in Africa, migrate out 60,000 years ago
- 40-50kya lives upper paleolithic lifestyle
Describe the mean value and variation in directional, stabilizing, and disruptive selection
- directional: average will change over time, variation will decrease gradually
- stabilizing: average will remain the same, variation will reduce (tail ends reduced)
- disruptive selection: average will remain the same, variation will increase
What is the cooking hypothesis
- homo Erectus used fire for warmth and food (evidence) but use of fire may have begun much earlier based off of morphological changes that occurred ~1.9 mya
Why is PICs important?
- to evaluate adaptations within taxa that are not evolutionarily independent
Describe observational research
- if experimental research is not feasible, observational research can answer questions
- in determining whether chimps and humans are related we can use comparative anatomy (which are supported by genetic comparison)
why is heritability often misinterpreted?
- Heritability within populations tells us nothing about causes of difference between population means in different environments
What is horizontal gene transfer?
common in prokaryotes; blurs line between species- not genetically cohesive
- differ from clonal (asexual) communities
- the non-sexual movement of genetic information between gnomes
- relevant to defining prokaryotic species
- ecological barriers maintain species boundaries
What is a cline?
Associated with parapatric speciation - neighbouring populations can experience different selective pressures
- forms a cline: a spatial gradient of genotype/phentoype frequencies - eventually leads to hybrid zone / speciation
What form of speciation forms a cline?
- a spatial gradient of phenotypic/genotypic frequencies in parapatric speciality
What occurs if one polypoid member mates with another of the same condition?
- if they manage to find another mate or self fertilize: leads to instant speciation - reproductively isolated
What are the two potential consequences of allopolyploidy?
- somatic doubling: two normal parent species with different chromosomal numbers mate - form inviable offspring who undergoes mitotic error and creates viable gametes that ti can self fertilize with to create a viable hybrid
or unreduced gametes: (non reduction) - two species, one parent does not divide - produced hybrid and normal game - forms viable fertile hybrid (can originate in parents or F1)
