early_atmosphere_revision Flashcards
What gases did volcanoes release into Earth’s early atmosphere?
Carbon dioxide (CO₂), water vapour (H₂O), and nitrogen (N₂).
How were the Earth’s early oceans formed?
Water vapour cooled, condensed, and fell as rain, forming the oceans.
What is another theory for how Earth’s water was supplied?
Icy comets rained down on Earth, melted, and added to the water supply.
What were the main gases in Earth’s early atmosphere?
Mainly carbon dioxide (CO₂), with some nitrogen (N₂) and water vapour (H₂O), but very little oxygen (O₂).
Which planets does Earth’s early atmosphere resemble?
Mars and Venus.
When do scientists think the first organisms formed?
About 3.4 billion years ago.
Which organisms were among the first to appear?
Bacteria and simple organisms like algae.
How did algae contribute to changes in the atmosphere?
They photosynthesised, releasing oxygen (O₂) into the air.
What happened to oxygen and carbon dioxide levels over time?
Oxygen (O₂) levels rose steadily, and carbon dioxide (CO₂) levels fell as algae and plants photosynthesised.
How did plants help shape Earth’s atmosphere?
As they evolved, they colonised land and increased oxygen levels.
What did higher oxygen levels allow?
The evolution of the first animals.
Why couldn’t most early microorganisms survive?
They evolved without oxygen, so they couldn’t survive in the higher O₂ concentration.
