1.5 The Evolution of the Atmosphere

Question 1

What occurred in the first billion years of the Earth’s history?

Answer 1

Lots of volcanic activity, the surface was covered in volcanoes that erupted and released lots of gases such as carbon dioxide and water vapour. Volcanic activity also released nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of ammonia

Question 2

What happened when the water vapour condensed?

Answer 2

It formed the oceans

Question 3

How was lots of carbon dioxide removed from the early atmosphere?

Answer 3

It dissolved in the oceans

Question 4

What happened to the dissolved carbon dioxide in the oceans?

Answer 4

It went through a series of reactions to form carbon precipitates that formed sediments on the seabed

Question 5

What was the first bacteria on the Earth called?

Answer 5

Cyanobacteria

Question 6

The first ________, followed by green plants and ______, evolved and absorbed some of the carbon dioxide so that they could carry out _______________ to produce glucose

Answer 6

Bacteria, algae, photosynthesis

Question 7

After the first bacteria, green plants and algae were formed, what else then evolved?

Answer 7

Marine animals - their shells and skeletons contained carbonates from the oceans

Question 8

What happened when plants, marine animals and plankton died?

Answer 8

• They fell to the seabed and got buried by layers of sediment
• Over millions of years, they became compressed and formed sedimentary rocks, oil and gas - trapping the carbon within them and keeping the carbon dioxide levels in the atmosphere reduced

Question 9

When did algae form on the Earth?

Answer 9

Around 2.7 billion years ago

Question 10

What is crude oil and natural gas formed from?

Answer 10

Mainly from dead plankton

Question 11

What is coal made from?

Answer 11

Thick deposits of dead plant material

Question 12

What is limestone formed from?

Answer 12

The calcium carbonate that marine organisms incorporate into their shells and skeletons

Question 13

Which evolved first: cyanobacteria, algae or green plants?

Answer 13

Cyanobacteria

Question 14

What happened when oxygen levels built up in the atmosphere?

Answer 14

More complex life (like animals) could evolve

Question 15

Describe the Earth’s atmosphere composition

Answer 15

• 78% nitrogen
• 21% oxygen
• Small percentages of other gases

Question 16

What is the word equation for photosynthesis?

Answer 16

carbon dioxide + water —> glucose + oxygen