L9

Question 1

Timeline of evolution

Answer 1

1900s
- Neo-Darwinian evolution

1920s-1930s
-Mathematics of gene frequencies

1945
- Attempts to bring palaeontology back into the fold

1953
- Crick and watson unravel DNA

1960s
- Genetic code established

1970s
- Technological innovation enables manual DNA sequencing

1980s
- Technological innovation enables identification of genes and gene function

1990s
- Automated DNA sequencing

2000s
- Whole genome sequencing and evo-devo research

Question 2

Palaeogenomics - Amber fossils

Answer 2

• As soon as an organism dies it becomes infested with microbes (internal and external) that contaminate DNA
  • DNA breaks down very quickly in the presence of water and/or air
  • Theoretical DNA could only be observed from more recent fossils

Question 3

Major and rapid advances in the last decade:

Answer 3

• Most of the genome of the woolly mammoth has been sequenced
  • We even know the nuclear gene for coat-colour polymorphism
  • We now know that the mammoth was more closely related to Asian rather than African elephant and the two diverged 6-7 million years ago
  • Neanderthals DNA has been sequenced
  • T-rex protein sequences obtained from bone-derived collagen

Question 4

Molecular taxonomy

Answer 4

• Entire genomes can be analyzed
  • Fossils along with living specimens can be made into a phylogeny
  • Fossils show unknown character combinations

Question 5

Molecular biogeography

Answer 5

• Multiregional vs out-of-Africa hypothesis
• multiregional describes long divergence time ago whereas out of Africa does not

Question 6

Molecular clocks

Answer 6

• Calculates divergence time
  • Tends to work for shallow dates but not very old dates
  • Because the genome doesn’t evolve at a constant rate eg during adaptive radiations

Question 7

In all cases fossils are incorporated into these analyses either to:

Answer 7

• Reflect evolutionary history (long extinct organisms and traits)
  • Provide and calibrate a time dimension

Question 8

Case stud: radiation of birds

Answer 8

• Birds evolve from small agile, feathered theropod dinosaurs by at least the Upper Jurassic
  • Traits evolve sequentially
  • Birds are neither common or diverse with the skies ruled by the pterosaurs
  • Many lose ability to fly
  • Still have other primitive characters

Question 9

Did the KT boundary wipe out dinosaurs…. or were there modern birds in the cretaceous period?

Answer 9

• Mot much evidence for modern birds in the cretaceous
  • Two major radiations, after KT and meioscene

Pterosaurs become extinct, birds appear to diversify as the Neognathae radiate. The vast majority of living birds are Neognathae with 8,500 species in 140 families

Question 10

Did the neognathae evolve after the KT mass extinction and fill the ecological vacuum left by pterosaur extinction?

Answer 10

-Depends on fossils used to calibrate

Question 11

Did the neognathae have a long cretaceous history but they were simply rare and not very diverse?

Answer 11

Evidence from:

Fossils
Phylogenetic analysis
Molecular clocks

Question 12

Developmental genetics

Answer 12

• Ability to identify genes and look at their function
  • Turning genes off and on
  • Can look at past character combinations
  • Speed of genome evolution

Question 13

Hox genes

Answer 13

• Can work out how evolution worked
  • Hox gene locations can be calculated
  • How hox genes form segmentations in different groups can be calculated