Lecture 27 Flashcards
What is the Bottom Up Origin of Life view?
Under early Earth conditions, what biochemical precursors can be produced
What is the Top Down Origin of Life view?
Comparing modern species and inferring back about last common ancestor. Looking at what’s shred
What did origional Tree of Life diagrams focus on and what did they ignore?
They focussed on phenotypic traits and eukaryotes. Ignored microbes
What did scientists find a difference in that lead to the split between archea and bacteria?
Ribosomal RNA’s
Describe the Modern Map in terms of the branches
- The tips of the branches are alive
- Internal branches represent ancestors
What does ‘LUCA’ represent?
Last Universal Common Ancestor
What does the majority of the Modern Tree consist of?
Microbes
What does ‘Candidate Phyla Radiation’ consist of?
Many symbiotes/pathogens
Describe the ‘Candidate Phyla Radiation’ genomes
- Small genomes
- Restricted metabolic capacities
- Lack of complete Citric Acid Cycle/Respiratory chains
- Limited/no ability to synthesise nucleotides/amino acids
What does a red dot by a lineage mean?
Unculturable
What two theories does the modern tree of life rely on?
- Molecular Clock
2. Nearly Neutral Theory
Describe the Molecular Clock
The number of mutations within biomolecules can be used to deduce when species diverged
->earlier divergence = less shared genes
Describe the Nearly Neutral Theory
- Most genetic variation between species is either neutral (no negative effect) or slightly deleterious and is fixed in population due to genetic drift
- > individuals with/without neutral variant have almost no difference in fitness
Why are viruses difficult to put into a tree?
Because there are no conserved genes across all viruses
How are viruses classifed?
Classified based on how they store their genetic material
