Average Process
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pattern
the change we see in the fossil record through time
mechanisms of evolution
- lamarckianism
- catastrophism
- mutationism
- scalae naturae
- orthogenesis
- theistic evolution
lamarckianism
an organism can pass on to its offspring physical characteristics that the parent organism acquired through during its lifetime
catastrophism
the Earth has largely been shaped by sudden, short-lived, violent events
mutationism
new species are formed from the sudden and unexpected emergence of alterations in their defining traits
scalae naturae
the great chain of being, a solid march towards perfection
orthogenesis
organisms have an innate tendency to evolve in a definite direction
theistic evolution
god started or directed evolutionary processes, divin creation
darwin's theory
individuals more suited to the environment are more likely to survive and therefore reproduce and leave their heritable traits to future generations
'pangenisis'
- darwin's hypothetical mechanism for heredity
- each part of the body continually emitted 'gemmules' that aggregated in the gonads
2 key rules of inheritance (mendel meets darwin)
- law of segregation (gametes)
- law of independent assortment (prophase 1)
the modern synthesis
- the fusion of mendelian genetics with darwinian evolution
- that selection due to environmental pressures can be propagated via heratibility through evolutionary time
what is a 'trait'
a pheontype under selection
3 types of selection
- stabilising (purifying)
- directional
- disruptive
stabilising (purifying) selection
- selection against extreme trait values
- phenotypic variation lost
- mean trait value stays the same
directional selection
- selection against extreme trait values
- mean trait value moves in response to the direction + intensity of the selection
disruptive selection
- selection against mean trait
- result is a multimodel trait distribution
any given phenotype is affected by...
its genetic bias as well as an environmental component
heritability of a given trait
- the ratio of the genetic variation to total phenotypic variation
- h* = V^G / V^P
phenotypic plasticity
the ability of one genotype to exhibit variable phenotypes when exposed to different environments
heritability to predict evolutionary change
R = h* S
R - evolutionary response
h* - heritability
S - selection differential
intrasexual selection
competition between members of the same sex (usually male) for access to mates
intersexual selection
where members of one sex (usually females) choose members of the opposite sex