Last part of 206 Flashcards
Species
Smallest evolutionarily independent unit
3 parts of speciation
- Reduced gene flow
- Genetic divergence
- Reproductive isolation
3 parts of reduced gene flow
- Physical (geographic/allopatric)
- ecological
- sexual
2 parts of physical isolation
- vicariance
- dispersal
2 parts of genetic divergence
- genetic drift
- adaptation to different habitats/resources
3 parts of reproductive isolation
- incidental genetic incompatibilities
- reinforcement
- sexual selection
Vicariance
- splitting event
Dispersal
- rare
- due to natural events like storms
Ecological isolation
- breeding habitat, time, behaviour, morphology (ex stickleback)
Sexual selection reduces gene flow if
- linkage between sexually selected trait and the preference for the trait
- variation for either the trait or the preference
Genetic divergence
- Bottleneck or founder effect, needs super strong drift
- low genetic variation
Ecological speciation
adaptation to diff habitats/environments
parallel adaptation in marine and freshwater sticklebacks
Reproductive isolation 2 times
Prezygotic
Postzygotic
Incidental genetic incompatibilities due to drift or selection
Alleles don’t work together (Bateson dobzhansky-muller)
Reinforcement
Selection against offspring of mixed matings
Basically postzygotic incompatibilities unknown to the animal so selection forms exaggerated differences
What is needed for pops to diverge with gene flow
selection needs to be higher than migration
Sympatric speciation
In 1 area
Parapatric speciation
adjacent areas
Hybridization
breeding between individuals from genetically different populations or species
Introgression
Transfer of genetic material between individuals from genetically different populations or species facilitated by hybridization
Hybrid fitness increase intrinsic causes
- masking of deleterious recessive alleles
- Increase in heterozygote advantage
Hybrid fitness increase extrinsic cause
- introduction of new adaptations
Hybrid fitness decrease intrinsic causes
- chromosomal incompatibilities
- loss of coadapted gene complexes
Hybrid fitness decrease extrinsic cause
- loss of local adaptations (goats that died)
Hybrid low fitness
Reinforcement - finalization of reproductive isolation
Hybrid reproductively isolated from parent species
- polyploid hybrid speciation (ploidy increased, in plants lots)
- homoploid hybrid speciation (ploidy doesn’t change. lonely finch with lots of inbreeding)
Hybrid and offspring and grand-offspring high fitness (heterosis)
Reverse speciation/adaptive introgression (mallard duck with grey duck/insecticide resistance in mosquitoes)
Hybrid has high fitness in hybrid zone
Stable hybrid zone
Adaptive radiation
rapid proliferation of new species from single ancestral species
sympatric
Darwin finches speciation type
Allopatric? evolved on separate islands and spread
Sympatric? In parallel within each island
3 Species with alot of admixture
Due to beak
Tapirus distribution
weird
originated in western asia and then spread everywhere else
Biogeography
study of where organisms live and how they got there
phylogeography
study of geographic distribution of evolutionary lineages, use of evolutionary trees to answer questions about distribution of organisms
Why are they where they are
Speciation in situ (vicariance)
Dispersal
Why are they not where theyre not
Range limited by barriers to dispersal, fundamental ecological niche, biotic interactions
5 effects of climate change
- distribution shift
- declining habitat size
- dispersal barrier
- limited dispersal ability
- range expansion (rare)
Prevents fundamental niches from expanding through adaptation (stasis promotion)
- Migrational load/gene swamping/ maladaptive introgression
- genetic variation
- genomic/developmental constraints
Where species diversity is high
at low altitudes
areas of high primary productivity
areas with moderate disturbance rate
larger islands and continents
phyletic gradualism
morphological evolution is gradual and unrelated to speciation
Saltation
sudden changes in morphology
Stasis
no changes
Punctuated equilibrium
long stasis and quick saltation together
causes of punctuated equilibrium 3
- artifact of fossil record
- extreme pattern resulting from random processes
- macroevolution involves species selection
fossil record to demonstrate punctuated equilibrium needs
- species and phylogony defined independently of morphology
- dense sampling from many locations
What causes stasis
- kind of stabilizing selection/niche conservation
- definitely genomic and development constraints
what causes saltation
ecological release and evolutionary innovation
3 ways evolutionary innovations arise
- modularity
- specialization
- co-option (exaptation)
Modularity
- made of modules
- key innovations arise in changes of modules in number or use
- Heterochrony
- Heterotopy
- allometry
Heterochrony
changes in timing of development
Heterotopy
Changes in spatial relationships among part
allometry
changes in growth rates of parts
specialization
willinston’s law
against redundance
willinston’s law
parts in organism tend toward reduction in number with fewer parts very specialized
co-option
modification of existing protein/structure/behaviour for a new function
hox genes (homeotic)
set up segments with developmental fates
serial expressions
Hox genes duplications
1 st made chordates and 2nd made vertebrates
Complex systems evolved
bringing different regulatory genes and their networks together to not have just 5% of a structure
Spinnerets are what
serial homologs of pedipalps and limbs
How different are humans and chimps
1% genetic divergence
3 hypotheses of humans arising
african replacement
multiregional evolution
hybridization and assimilation (this one)
Can selection explain deviant social behaviour
yes. Evolutionary psychiatry like risk of parental homicide is higher for stepchildren
Why do genetic diseases exist and persist
- mutation
- founder effects
- heterozygote advantage
- linkage
- adaptational lags
Is selection being eliminated by human ingenuity
- niche reconstruction
- memes
- coltural change
cultural change is like natural selection
- individuals vary
- variation is transmitted among individuals
- some variants are more successful than others
Because mutation rate is high and generation time is low
biological evolution is lagging behind many aspects of cultural evolution leading to diseases of civilization
adaptational lag is partially mitigated but also exacerbated
Primary goal of conservation
maintenance of potential for pops to adapt, evolve and form new species
genetic problems in conservation management involve
careful delineation of genetic population units
conservation breeding programs
restoring natural gene flow
careful delineation of genetic pop units
cryptic species, evolutionarily significant units, management units
cryptic
look the same but they’re different
evolutionarily sig units
genetically isolated pops
management units
diff birth or death rates, different threats
conservation breeding programs
germ plasm banking
captive breeding
in situ breeding management
restoring natural gene flow
habitat corridors
translocating individuals/ seeds
eliminating alien species
Genetics help understand
ecology, monitoring populations, law enforcement
population decline genetic results
non random mating
loss of adaptive potential
nonrandom mating
inbreeding depression
hybridization inihiliation
loss of adaptive potential due to
loss of genetic additive variation
increase in genetic drift
habitat degradation has 3 responses
phenotypic plasticity
migration
genetic adaptations
