Lecture 9 -fossils and the molecular revolution Flashcards
when was mendels work rediscovered and a theory of heredity integrated into darwins evolutionary theory to create neo-darwinian evolution?
1900
what are Fisher, Haldane and Wright known for doing in the 1920s-1930s?
hardened neo-darwinian evolution into the modern synthesis as mathematics of gene frequencies were explored
what did George Gaylord Simpson in 1945 do to bring palaeontology back into the fold after it had been lost for many years?
published ‘tempo and mode of evolution’ - used fossils to test fishers theories
when did crick and watson unravel the structure of DNA?
1953
when was the genetic code established?
1960
what sequence of events happened in the 1970s, 1980s, 1990s in terms of genes?
1970 - manual DNA sequencing
1980 - identification of genes and gene function
1990 - automated DNA sequencing
what was the first humans DNA sequenced?
2004
what progress happened in the 2000s in regards to DNA sequencing
whole genome sequencing and Evo-devo research intensifies as technological development intensifies in terms of sequencing ability
why was it thought unlikely that you could get DNA from fossils?
as soon as an organism dies it becomes infested with microbes (internal and external) that contaminate DNA - even in the case of amber fossils
- DNA breaks down very quickly in the presences of water and/or air
what did a research paper in 1997 state about DNA from fossils?
the older fossils are the more you loose DNA preservation - DNA in the fossils breaksdown unless they are from the past 50,000 years
how was most of the genome of the wolly mammoth sequenced?
- frozen DNA from the frozen juvenile mammoth was well preserved
- now even know the nuclear gene for coat-colour polymorphism
by comparing DNA of fossils to their extant relatives what could we find out about the wolly mammoth?
- more closely related to Asian elephants rather than African
- the mammoth and Asian elephant diverged 6-7 million years ago
what type of studies help us to work out divergence times?
molecular clock studies
what is the issue with DNA from dinosaur fossils?
- the further back in time the DNA breaks down unless there is exceptional preservation
what is now being done to look at dinosaur DNA?
look at proteins e.g. t-rex proteins sequences have been obtained from bone-derived collagen
what 3 things caused the molecular revolution?
1) molecular taxonomy
2) molecular biogeography
3) molecular clocks
what is molecular taxonomy and the advantage of it?
when doing a phylogenetic analysis run cladistics on molecular characteristics
- can now join morphological and molecular cladistic analyses to form ‘super trees’
- can add in fossils that you only have morphological characteristics of into the cladistic analysis and get more accurate outputs
what is an example of when molecular biogeography has been used to solve a debate?
- genetic analysis to help solve the OOA debate - concluded due to the greater genetic diversity of Africans that the OOA hypothesis is more likely
how are fossils useful for molecular clocks?
- fossils can be used to calibrate molecular clocks
- molecular clocks work by getting part of the genome thats not under selection pressure and it will neutrally bring up mutations - can work out when species diverged by looking at their differences
- assume that the mutations happen at a steady rate i.e use fossils for calibration
what is an issue with molecular clocks?
often come out alot older
what did birds evolve from?
small, agile, feathered theropods = runaway/macroevolution
- as they got smaller, brains got bigger and flight evolved = modern day birds
what happened in the Jurassic to alot of the newly evolved birds?
- lots lost their flight because of competition with pterosaurs that ruled the skies
what impact did the KT bollide impact have on birds?
the mass extinction cleared the sky causing a post KT diversification of Neognathe (modern birds)
what are the vast majority of living birds?
neognathe with 8,500 species in 140 families
what are the 2 hypotheses for what happened regarding the evolution of Neognathe?
1) the neognathe evolved after the KT mass extinction and filled the ecological vaccum left by pterosaur extinction
2) the neognathe have a long cretaceous history but they were simply rare and not very diverse
what are three ways to get evidence to address the hypotheses about neognathe evolution?
1) fossils (however, its bias and incomplete with not enough neognathe fossils found)
2) phylogenetic analysis - using modern birds and evidence we have from fossil - fits that neognathe are more derived
3) molecular clocks - suggests neognathe existed already but diversified after KT impact rater than the whole group evolving rapidly at the boundary
what does evo-devo research enable us to do?
enables us to identify genes and their functions - can then establish their distribution among living organisms and decipher where they evolved on a phylogeny and what functions they perform i.e how they have been passed on
what does the fossil record help with in developmental genetics?
enables us to date events i.e establish the timing and nature of character acquisition, determine past character combinations and estimate the speed of genome evolution
what do fossils morphological characteristics help with?
can relate morphological development to molecular development
- shows us about the history of life
