2 - Evolution And Diversity Flashcards
Surface origin hypothesis
‘Warm little pond’
- Primordial soup - evidence that organic molecules can form spontaneously)
- Unlikely due to hostile conditions on surface?
- High UV, meteor strikes, volcanic activity
Subsurface origin hypothesis
Hydrothermal vents at ocean floor
More stable conditions than surface (high UV, meteor strikes etc.)
Constant source of energy (reduced inorganic compounds)
Origins of cellular life
- key features
Cellular life arises around inorganic ions and other compounds (Oxygen, CO2 etc.)
- no organic starting material
Key features:
- Self replicating RNA (RNA world, ribozymes)
- Enzymatic proteins - from mutations in RNA ribozymes
- DNA - genetic code - as RNA is very unstable - DNA more stable, less chemically active
- Evolution of biochemical pathways (respiration etc.)
- Divergence of lipid biosynthesis
- Divergence of cell walls - increased chance of survival in more adverse conditions
- all features allow something like bacteria or archaea to exist
Ribozyme def
Something that can catalyse chemical reactions
- e.g. ribosomes - uses RNA in its processes
Landmarks in biological evolution
- early life dependent on H2 and CO2 - used to make acetate and methane
- bacteria making acetate
- archaea making methane
- energy and carbon metabolisms diversify
- phototrophy - using H2S as electron donor
- evolved into oxygenic photosystem using H2O
- this started oxygenation of atmosphere
- first eukaryotes will start to develop and use oxygen as final electron acceptor for respiration
Methanogenesis equation
(Production of methane)
CO2 + 4H2 —> CH4 + 2H2O
Anoxygenic photosysnthesis
H2S —> S0 + 2H
- reduction of hydrogen sulfide
Oxygenic photosysnthesis equation
- how can enzymes do this
2H2O —> O2 + 4H
- not much change needed for enzymes involved in anoxygenic photosynthesis with hydrogen sulfide, to use water
(Oxygen in same group as sulfur)
Phylogenetic method analysis of DNA - example
- Isolate DNA from cells
- PCR to amplify DNA
- DNA sequencing
- sequence analysis
- generate phylogenetic tree by comparing relationship between DNA sequences
Marker molecules used in diversity studies
- what traits do they need
- certain molecular sequences are useful in phylogenetic analysis
- must be universal
- contain variable and conserved regions
- must not be subject to horizontal gene transfer
- must be truly homologous
- Ribosomal RNA genes are a universal molecular marker as they are present in all forms of life
- Present in LUCA
- Other markers: ATPase subunits, EF-Tu, RecA
What molecule usually used in phylogenetic trees and analysis
Ribosomal RNA - used in most sequencing
Endosymbiosis theory
A eukaryotic organism captures a prokaryote and incorporates it into its structure
- e.g. mitochondria and chloroplasts for respiration and photosynthesis
- carbon fixation in chloroplasts
Evolution of eukaryotes theories
Endosymbiont theory:
- Mitochondria - incorporation of aerobic chemo-organotrophic bacteria into a host (bacterial?) cell
- Chloroplasts: incorporation of photographic Cyanobacteria info a eukaryotic cell
Hydrogen hypothesis:
- association of an archaeal host using H2 as energy source with an aerobic bacterium that produced hydrogen as a ‘waste’ product
Are humans more related to archaea that live in harsh conditions or prokaryotes - bacteria
Archaea - look at phylogenetic tree
Aquifex aeolicus bacteria info
(Maybe not needed)
- isolated from a hot spring
- hyperthermophilic (grows in up to 95C)
- chemolithoautotroph - oxidised H2 to water using O2 as electron acceptor
- Autotrophic - Carbon fixation
