Option D Evolution (D1)

• 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

Miller and Urey

1953

Ammonia (NH₃), methane (CH₄), hydrogen (H₂)

• 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).

Water containing membrane bound microspheres that is viscous and cloudy in appearance.

Primitive cell like structures, that may have preceded living cells.

RNAs can store, transmit and replicate genetic information

• 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

The theory that chloroplasts and mitochondria were once free-living prokaryotes that were engulfed by larger prokaryotes. These then evolved into organelles of eukaryotes.

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)