Option D Evolution (D1)
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Name 4 processes needed for the first cells to form.
- 1. Chemical reactions to produce simple organic molecules
- 2. Assembly of the above molecules into polymers
- 3. Formation of polymers that can self replicate
- 4. Development of membranes to form spherical droplets with internal chemistry different from external
Name the guys involved in an experiment that simulated the begninnings of life on earth.
Miller and Urey
What year did Stanley Miler and Harold Urey do their seminal experiment?
What gases did Miller and Urey include in their experiment?
Ammonia (NH3), methane (CH4), hydrogen (H2)
Name at least 3 locations that have been sugested for the synethesis of the organic compounds needed for the origin of life.
- 1. Chemical reactions in the atmosphere and in water, on the surface of the earth
- 2. Hydrothermal vents
- 3. Extraterrestrial origin (there was a heavy bombardment of the Earth by meterorites 4000 million years ago which may have brought the organic compounds
- 4. Near volcanoes (It spews out water vapour, other gases and various minerals which could be used to form organic matter)
- 5. Alternating wet/dry conditions (Seashore or flood plains of a river where there are alternating wet/dry conditions could provide a place for catalysing reactions and forming early organic molecules).
What is a coacervate?
Water containing membrane bound microspheres that is viscous and cloudy in appearance.
What is a protobiont?
Primitive cell like structures, that may have preceded living cells.
Outline 2 properties of RNA that would have allowed it to play a role in the origin of life
RNAs can store, transmit and replicate genetic information
Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere
- 1. Around 2 billion years ago a form of chlorophyll appeared in bacteria that allowed photosynthesis
- 2. The oxygen content rose to 0.45%. This coincides with the rise of the Eukaryotes
What is the endosymbiotic theory?
The theory that chloroplasts and mitochondria were once free-living prokaryotes that were engulfed by larger prokaryotes. These then evolved into organelles of eukaryotes.
What is the evidence for the endosymbiotic theory?
Characteristics of mitochondria and chloropasts support endosymbiotic theory.
- *Both grow and divide like cells
- *Have a naked loop of DNA (like prokaryotes)
- *Synthesize some of own proteins using 70S ribosomes, like prokaryotes
- *Have double membranes (as expected when cells are taken into a vesicle by endocytosis)
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