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CognitoEarth's atmosphere — evolution and composition
Key facts & methods
Current composition of the atmosphere — fill in the table
| Gas | % of atmosphere |
|---|
| Nitrogen (N2) | |
| Oxygen (O2) | |
| Argon (Ar) | |
| Carbon dioxide (CO2) | |
| Water vapour | |
| Noble gases (He, Ne, Kr, Xe) | |
Evolution of the atmosphere — fill in the table
| Stage | What happened |
|---|
| 4.6 billion years ago | |
| Volcanic activity | |
| Water vapour condensed | |
| Photosynthesis | |
| Nitrogen | |
Evidence for atmosphere changes — fill in the table
| Evidence | What it shows |
|---|
| Carbonate rocks (limestone) | |
| Iron-banded formations | |
| Fossils of early photosynthetic organisms | |
| Gas bubbles in ancient ice cores | |
| Mathematical models | |
Role of key processes — fill in the table
| Process | Effect |
|---|
| Photosynthesis | |
| Respiration and combustion | |
| Dissolution in oceans | |
| Formation of fossil fuels | |
| Maintaining current balance | |
Exam questions — 4 questions · 10 marks · AQA 8462 style
⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
1 markAtmosphere compositionAQA 8462 style
Approximately what percentage of the current atmosphere is nitrogen?
3 marksEvolution of atmosphereAQA 8462 P1 style
Explain how the level of oxygen in the atmosphere increased over billions of years. (3 marks)
Hint: Start with: early atmosphere had no O2. Explain: photosynthesis by early organisms produced O2. Over billions of years O2 accumulated.
+30 XP
1 markCO2 decreaseAQA 8462 style
Which of the following is NOT a reason why CO2 levels decreased in the early atmosphere?
A CO2 dissolved in oceans
B Photosynthesis removed CO2
C CO2 was converted to oxygen by volcanic activity
D Formation of carbonate rocks (limestone) locked up carbon
3 marksRole of oceansAQA 8462 style
Explain how the formation of oceans helped reduce the level of CO2 in the early atmosphere. (3 marks)
Hint: Chain: water vapour condenses → oceans form → CO2 dissolves in ocean water → carbonate rocks form → CO2 removed from atmosphere.
+30 XP
Quick recall flashcards
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