4.9.1.4 - How carbon dioxide decreased

What did algae and plants also do, other than increase the amount of oxygen in the atmosphere?

Algae and plants also decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.

What had evolved that contained carbonates from the oceans? (further decreasing carbon dioxide levels)

Later marine animals also evolved, and their shells and skeletons contained carbonates from the oceans

How else was carbon dioxide decreased from the atmosphere?

Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon - so some of the carbon these organisms took in from the atmosphere was locked in rocks and fossil fuels after the organism died

List the ways carbon dioxide is reduced.

• Photosynthesis

• formation of sedimentary rocks + fossil fuels

• carbonates within shells and skeletons

Describe the formation of fossil fuels

When plants, plankton and marine animals die - they fall to the seabed and get buried by layers of sediment.

Over millions of years, they become compressed and form sedimentary rocks, oil and gas - trapping the carbon. 

This is how fossil fuels are made

What is crude oil and natural gas formed from?

Crude oil and natural gas are formed from the deposits of plankton

This is how fossils form reservoirs under the seabed when they get trapped in rocks

What is coal and what is it made from?

Coal is a sedimentary rock

That is made from thick plant deposits

What is limestone?

Limestone is a sedimentary rock

What is limestone made from?

Mostly made up of calcium carbonate deposits from the shells and skeletons of marine organisms