Rates of Evolution Flashcards
what was darwis view?
that evolution proceeds gradually
what did the discovery of mendelian genetics show?
discrete units of hereditry were inconsistent with continuous range of variation seen in nature - big changes should be more common
what was the modern synthesis?
evolution framed as ‘changes in allele frequencies w/in pops’
the four forces of evolution?
drift, gene flow, mutations, ns
what did darwins original ideas see?
extinction events, diversification, stasis, new species/types/clades
what was the general overview? darwin and neo?
rate was - gradual morphological change over time
neo - same - gradual change in gene frequencies
what is macroevolution?
origin of major changes in morphology or body plan
what was the decision in the 1980’s?
neo-darwinism is wrong and evolution is not characterised by gradual anagenesis
what is anagenesis?
gradual change within a lineage
what is cladogenesis?
when one lineage splits in two
what is phylogenetic gradualism and what was the verdict on it?
it was rejected
the pattern of gradual change over time, such that trait morphology change is not associated with cladogenesis
what is punctuated equilibrium?
abrupt changes, most frequent pattern in the fossil record
what are the implications of punctuated equlibrium?
new species suddenly appear
intermediates rarely found
macroevolution
how does PE imply macroevolution occurs?
lineage splitting rapidly lineages stable between changes in small geographically isolated populations changes in few key loci
evidence for PE?
molluscs - speciation in Cenazoic
claimed to have punctuated diversification in two time periods - not gradualistic
bryozoans - found not much change within species but sudden appearance of new species - was persistance of ancestor species
counter evidence for PE/
trilobites
found 8 lineages w/ changes in the number of pygidial ridges w/ time
‘end’ members had previously been assigned to a different species
what did JBS Haldane do?
came up with an equation that expressed morphological change in darwins
commonly used in studies of fossil record
can compare rates of evolution that occured over different time periods in different lineages - for a single trait
what did Gingerich do?
looked at rates of morphological evolution, scale to look at variability in rates
I - v high - lab selection experiments
II - high - adaptive radiation
III - moderate - faunal changes since glaciation
IV - low - fossil record
when will negeative relationships between evolutionary rate and time interval be found?
if the direction of evolution fluctuates over time
is PE a problem for neo-darwinism?
abrupt morphological change likely not a characteristic of how evolution proceeds
is stasis a problem for neo-darwinism?
stasis does not mean evolution has stopped, its not a result of reduced genetic variation
what is the debate in the molecular era?
want to map genotypes to phenotypes to find loci that matter for evolution
why do we look for QTL?
its the region of chromosome that correlates with phenotypic variation - so we assume we should find few large QTL and that they’re sometimes hard to find
what do we expect if evolution proceeds by phyletic gradualism?
that we won’t find few loci of large effect
