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How do alkali vents form?
A tectonic crack opens magma up to the sea. The hydroxide minerals that cooled into serpentine rock as a result formed alkali vents.
Name the 5 conditions for amino acid synthesis and how alkali vents supply them.
- 1. Miller-Urey compounds - reduction of seawater components to ammonia, methane and hydrosulphide.
- 2. Concentration of compounds - internal vent cells.
- 3. Catalyst - Fe-S
- 4. Thermochemical gradient - provided by magma.
- 5. Hydrogen gas for free energy.
What properties did LUCA possess?
Membranes, ATP, nucleic acids and basic metabolism.
Name 3 processes the presence of acetyl thioesters provided to early life.
Acetyl thioester - provides reducing power, converts CO2 into pyruvate and PO3 into an ATP alternative.
What early process may have been used for carbon compound synthesis and what were its requirements?
Reverse-Krebs cycle. Hydrogen ions, carbon dioxide and ATP.
Why is RNA a good candidate for the early nucleic acid used?
RNA can catalyse, bind to itself and bind to other stuff (e.g. proteins, amino acids).
If a 2-base RNA code was used, what would each base correlate with?
- 1st base - specifies precursor molecule and correlates with biosynthetic pathways.
- 2nd base - specifies product molecule.
What gradient facilitates amino-carboxy fusion in vent cells?
Why is the likely that DNA evolved from RNA?
DNA is more stable and permanent and can be derived chemically from RNA i.e. uracil to thymine, ribose to deoxyribose.
How might membranes have come about if the vent theory is to be believed?
A froth of Fe-S bubbles around the vent may have been gathered a protein coat, as it acts catalytically. Compounds diffuse from the catalyst source and collide, forming a membrane.
Why did the GOE cause an Ice Age?
Conversion of methane to carbon dioxide resulting in global temperature drop due to methane being a more powerful greenhouse gas than carbon dioxide.
What could have caused the time lag in the GOE?
Slow accumulation of oxygen producing life forms e.g. cyanobacteria, which was soaked up by iron bacteria. This maintained an equilibrium before photosynthesising organisms reached sufficient numbers.
What were the requirements of primitive photosynthesis?
Photosystems, pigments, ATP synthesis, rubisco or equivalent, Mn cluster or equivalent.
Give five features of a semi-autonomous organelle.
Genome, transcription / translation machinery, distinct biogenesis, specific function, self-replication by binary fission
Define deterministic and stochastic in terms of microevolutionary pressures.
- Deterministic - non-random
- Stochastic - random
Give four processes that increase variation in a population.
Mutation, recombination, sexual reproduction, gene flow.
Give three processes that decrease variation in a population.
Natural selection, sexual selection, genetic drift.
Define the 3 selection mechanisms that act on continuous variation.
- Stabilising - extremes selected against.
- Directional - 1 extreme selected against.
- Disruptive - extremes selected for.
Define gene flow.
Movement of individuals between gene pools (immigration or emigration).
Define genetic drift.
Stochastic allele frequency shift in small populations. May be caused by bottleneck or founder effect.
Define cladogenesis and anagenesis.
- Cladogenesis - transformation
- Anagenesis - branching
Give examples of pre-zygotic RIMs and post-zygotic RIMs.
- Pre-zygotic - ecological, behavioural, mechanical, gametic, temporal
- Post-zygotic - hybrid inviability, hybrid sterility, hybrid zygotic breakdown.
Are RIMs intrinsic or extrinsic?
Give the 3 models of speciation.
- Allopatric - apart. Barrier to gene flow e.g. founder effect, physical barrier.
- Parapatric - beside. Weak gene flow.
- Sympatric - together. Some individuals explore a new niche.
What are the 5 mating systems?
- Monogamy - 1 partner.
- Polygamy - multiple females per male
- Polyandry - multiple males per female
- Polygynandry - multiple other partners per mate
- Promiscuity - slutting around with no commitment.
How might a male impress a female?
Advertise genetic benefits, have a strategic handicap, defeat opposition, defend high quality territory.
Which genes encode regulatory proteins and operate in different parts of the body?
What is the Biological Species Concept?
A species is an isolated gene pool under the influence of RIMs.