Evolution of the atmosphere

Question 1

Explain phase 1: Volcanoes gave out gases…

Answer 1

1. Earths surface molten/any atmosphere boiled away
2. Things cooled down/thin crust formed/volcanoes still erupting.
3. Volcanoes gave out lots of gas
4. Mostly Co2, also water vapour which condensed to form oceans.

Question 2

Explain phase 2: Green plants evolved and produced oxygen..

Answer 2

1. Green plants/algae evolved/happy with Co2
2. Early Co2 dissolved in oceans and green plants/algae absorbed Co2 and produced O2 by photosynthesis.
3. Plants/algae died/buried under sediment/carbon/hydrocarbons locked in sedimentary rock as carbonates/fossil fuels.

Question 3

Explain phase 3: Ozone layer allows evolution of complex animals…

Answer 3

1. Build up of oxygen killed early organisms but more complex organisms evolved.
2. Oxygen created the ozone layer which blocked harmful rays from the sun and enabled even more complex organisms to evolve.
3. Barely any Co2 left now.

Question 4

Explain the primordial soup theory.

Answer 4

1. Billions of years ago, the Earth’s atmosphere contained hydrocarbons, ammonia etc.
2. Lightning struck which caused a chemical reaction between the gases resulting in the formation of amino acids.
3. The amino acids collected into a body of water. (primordial soup)
4. The amino acids gradually combined to produce organic matter which eventually evolved into simple living organisms.