A2.1.1 Conditions on early Earth and the pre-biotic formation of carbon compounds (HL only)

What was the composition of the primordial atmosphere on early Earth?

High levels of CO₂, abundant CH₄, water vapor, nitrogen, hydrogen, and notably absent free oxygen (O₂).

What type of atmosphere did early Earth have?

A reducing atmosphere that readily donated electrons during chemical reactions.

What role did UV radiation play in early Earth's environment?

It provided the energy needed to drive chemical reactions, acting as nature's laboratory equipment.

How did electrical discharges contribute to pre-biotic chemistry?

They provided intense bursts of energy, created reactive species, and formed simple organic molecules.

What was one of the contributions of volcanic activity to early Earth?

Volcanoes released essential gases, provided heat energy, and created mineral-rich environments.

What was the basic recipe for the formation of simple organic molecules?

Simple gases (CO₂, CH₄, NH₃, H₂O), energy sources, and time. Carbon dioxide, methane, ammonia, water vapor.

What is an example of a simple reaction in the primordial soup?

Carbon dioxide plus hydrogen gas reacts to form formaldehyde and water.

What dual role did water play in early Earth?

As a solvent for reactions and as a protective shield from UV radiation.

How should early Earth's oceans be characterized?

They were likely hot, acidic, and mineral-rich, resembling natural chemical reactors.

What natural features protected forming organic molecules?

Deep ocean environments, clay minerals, rock crevices, and mineral surfaces.

What factors contributed to the higher temperatures on early Earth?

Frequent meteor impacts, intense volcanic activity, and the greenhouse effect from CO₂ and water vapor.

What was the concentration problem for the emergence of life?

Organic molecules needed to form in sufficient quantities, concentrate in specific locations, and persist long enough to interact.

What environments acted as nature's test tubes for molecular interaction?

Tide pools, hydrothermal vents, and mineral surfaces.

How did simple molecules evolve into more complex ones?

Simple molecules gradually formed more complex ones, such as amino acids into peptides and nucleotides into RNA-like molecules.

What does the process of building complexity in organic molecules indicate?

It wasn't linear or quick; it likely took millions of years of chemical evolution before self-replicating molecules appeared.