Lecture 9 -fossils and the molecular revolution

Question 1

when was mendels work rediscovered and a theory of heredity integrated into darwins evolutionary theory to create neo-darwinian evolution?

Answer 1

1900

Question 2

what are Fisher, Haldane and Wright known for doing in the 1920s-1930s?

Answer 2

hardened neo-darwinian evolution into the modern synthesis as mathematics of gene frequencies were explored

Question 3

what did George Gaylord Simpson in 1945 do to bring palaeontology back into the fold after it had been lost for many years?

Answer 3

published ‘tempo and mode of evolution’ - used fossils to test fishers theories

Question 4

when did crick and watson unravel the structure of DNA?

Answer 4

1953

Question 5

when was the genetic code established?

Answer 5

1960

Question 6

what sequence of events happened in the 1970s, 1980s, 1990s in terms of genes?

Answer 6

1970 - manual DNA sequencing
1980 - identification of genes and gene function
1990 - automated DNA sequencing

Question 7

what was the first humans DNA sequenced?

Answer 7

2004

Question 8

what progress happened in the 2000s in regards to DNA sequencing

Answer 8

whole genome sequencing and Evo-devo research intensifies as technological development intensifies in terms of sequencing ability

Question 9

why was it thought unlikely that you could get DNA from fossils?

Answer 9

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

Question 10

what did a research paper in 1997 state about DNA from fossils?

Answer 10

the older fossils are the more you loose DNA preservation - DNA in the fossils breaksdown unless they are from the past 50,000 years

Question 11

how was most of the genome of the wolly mammoth sequenced?

Answer 11

• frozen DNA from the frozen juvenile mammoth was well preserved
• now even know the nuclear gene for coat-colour polymorphism

Question 12

by comparing DNA of fossils to their extant relatives what could we find out about the wolly mammoth?

Answer 12

• more closely related to Asian elephants rather than African
• the mammoth and Asian elephant diverged 6-7 million years ago

Question 13

what type of studies help us to work out divergence times?

Answer 13

molecular clock studies

Question 14

what is the issue with DNA from dinosaur fossils?

Answer 14

• the further back in time the DNA breaks down unless there is exceptional preservation

Question 15

what is now being done to look at dinosaur DNA?

Answer 15

look at proteins e.g. t-rex proteins sequences have been obtained from bone-derived collagen

Question 16

what 3 things caused the molecular revolution?

Answer 16

1) molecular taxonomy
2) molecular biogeography
3) molecular clocks

Question 17

what is molecular taxonomy and the advantage of it?

Answer 17

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

Question 18

what is an example of when molecular biogeography has been used to solve a debate?

Answer 18

• genetic analysis to help solve the OOA debate - concluded due to the greater genetic diversity of Africans that the OOA hypothesis is more likely

Question 19

how are fossils useful for molecular clocks?

Answer 19

• 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

Question 20

what is an issue with molecular clocks?

Answer 20

often come out alot older

Question 21

what did birds evolve from?

Answer 21

small, agile, feathered theropods = runaway/macroevolution

- as they got smaller, brains got bigger and flight evolved = modern day birds

Question 22

what happened in the Jurassic to alot of the newly evolved birds?

Answer 22

• lots lost their flight because of competition with pterosaurs that ruled the skies

Question 23

what impact did the KT bollide impact have on birds?

Answer 23

the mass extinction cleared the sky causing a post KT diversification of Neognathe (modern birds)

Question 24

what are the vast majority of living birds?

Answer 24

neognathe with 8,500 species in 140 families

Question 25

what are the 2 hypotheses for what happened regarding the evolution of Neognathe?

Answer 25

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

Question 26

what are three ways to get evidence to address the hypotheses about neognathe evolution?

Answer 26

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

Question 27

what does evo-devo research enable us to do?

Answer 27

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

Question 28

what does the fossil record help with in developmental genetics?

Answer 28

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

Question 29

what do fossils morphological characteristics help with?

Answer 29

can relate morphological development to molecular development
- shows us about the history of life