D.1.1 Describe the 4 processes needed for the spontaneous origin of life on Earth

3. Formation of polymers that can self

replicate- this allows inheritance of

characteristics.

4. Development of membranes, to form

spherical droplets, with an internal

chemistry different from the surroundings,

including polymers that held genetic

information.

1. Chemical reactions to produce simple organic molecules from inorganic molecules:

Amino acids, Water, CO2, Ammonia.

2. Assembling of these organic molecules into polymers: Polypeptides from amino acids.

D.1.2 Outline the experiments of Miller and Urey into the origin of organic compounds

Reproduction of environment that existed before on Earth :

1. Methane, Hydrogen, Ammonia inserted

2. Water cycle simulation; heat –evaporate-cooled-condensed

3. UV radiation (no ozone layer before)

4. Electrical sparks = lightning

D.1.3 State that comets may have delivered organic compounds

Panspermia- the theory concerned with the arrival of material from outer space.

Hundreds of meteorites and comets hitting the early Earth brought with them organic

molecules formed by abiotic reactions in outer space.

Extraterrestrial organic compounds, including amino acids, have been found in modern

meteorites, and it seems likely that these bodies could have seeded the early Earth with

organic compounds.

D.1.4 Discuss possible locations where conditions would have allowed the synthesis of organic compounds

Tidal pools (clay-catalyst

polymerisation, minerals)

Deep sea thermal vents (heat, minerals in water)

Volcanoes (water vapours, minerals, heat)

In space (amino acids in dust)

D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life

D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life

1. RNA can self-replicate

Short polymers of ribonucleotides can be synthesized abiotically in the laboratory.

If these polymers are added to a solution of ribonucleotide monomers, sequences

up to 10 based long are copied from the template according to the base-pairing

rules.

If zinc is added, the copied sequences may reach 40 nucleotides with less than

1% error.

2. RNA can act as an enzyme – Ribozymes.

D.1.5 Outline two properties of RNA that would have allowed it to play a role in the origin of life

RNA can enzymatically catalyze metabolic reactions:

• RNA can catalyze the formation of more RNA

• RNA can bind amino acids and form peptide linkages

RNA-directed protein synthesis may have begun as weak binding of specific amino acids to

bases along RNA molecules, which functioned as simple templates holding a few amino

acids together long enough for them to be linked.

D.1.6 State that living cells may have been preceded by protobionts, with an internal chemical environment different

from their surroundings

A Protobiont is an aggregate of abiotically produced organic molecules surrounded by a

membrane or a membrane-like structure. Protobionts exhibit some of the properties

associated with life, including simple reproduction, metabolism and excitability, as well as

the maintenance of an internal chemical environment different from that of their

surroundings.

D.1.7 Outline the contribution of prokaryotes to the creation of an oxygen-rich atmosphere

Anaerobic bacteria are believed to be the first forms of life on

Earth. They consumed organic materials and reproduced to

such numbers that competition was high and food was

scarce. It is unclear how it happened but some bacteria

evolved to become photosynthetic.

 Photosynthetic prokaryotes began photosynthesis:

• Free oxygen is accumulated in the Earth’s

atmosphere.

• The formation of an ozone layer in the upper

atmosphere started.

• Incidence of UV light reaching the Earth’s surface

reduced thanks top ozone layer.

• Terrestrial existence (rather than life restricted to

below the water surface) became a possibility.

Stromatolites: Earth’s oldest fossil made of rock formed by growth of blue-green bacteria

Modern Cyanobacteria

D.1.8 Discuss the endosymbiontic theory for the origin of eukaryotes

Evidence for endosymbiotic theory:

Mitochondria and Chloroplasts have their own DNA; a naked loop

similar to that of prokaryotes. 

They have their own double membrane. 

They are able to replicate themselves

They have the ability to perform protein synthesis using ribosomes.