The Earth's atmosphere

Question 1

Proportions of gases in the early atmosphere and in the current atmosphere

Answer 1

80% nitrogen
20% oxygen

Small proportions of other gases

CO2
Water vapour
noble gases (group 0)

Question 2

What was the Earth’s early atmosphere formed by?

Answer 2

Intense volcanic activity

CO2
Water vapour
Nitrogen

Question 3

What happened as the Earth cooled?

Answer 3

Water vapour condensed to form oceans

Question 4

What was one theory about how the Earth’s early atmosphere was formed ?

Answer 4

Mainly CO2
Little/no oxygen gas

(Like Mars + Venus today)

Water vapour
Small proportions of methane (CH4) + ammonia (NH3)

Question 5

What was the Urey-Miller experiment?

Answer 5

Water
Ammonia
Methane
Hydrogen

High voltage spark to stimulate lighting

–> Amino acids, building blocks for proteins produced

Question 6

Miller + Urey used methane, ammonia + hydrogen + water for the Earth’s early atmosphere. Why?

Answer 6

these gases contain the elements in amino acids

Question 7

The experiment provides only weak evidence on how amino acids formed on Earth. Why?

Answer 7

nobody knows what was in the Earth’s early atmosphere

there may not have been (continuous) lightning

Miller and Urey selected only the gases needed to produce amino acids

Question 8

How was oxygen produced?

Answer 8

Photosynthesis of plants + algae

CO2 taken in O2 released

Question 9

What is “primordial soup” theory?

Answer 9

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