Yr 11 Earth and Environmental Science

1. Yr 11 Earth and Environmental Science Planet Earth and its Environment- FA4

2. DP1-Identify photosynthetic bacteria as the first organisms to release oxygen into the environment • Cyanobacteria, the first organisms capable of photosynthesis, appeared earlier than 3000 million years ago. • They actively produced their own fuel for respiration (sugars) making them more efficient • These organisms produce oxygen as a waste product. • At the time of their occurrence there was also a rise in the volume of oxygen gas in the atmosphere

3. DP1- Identify photosynthetic bacteria as the first organisms to release oxygen into the environment • Oxygen is an extremely reactive element that readily bonds with many other elements, particularly active metals like iron. • As the first photosynthetic organisms released oxygen into their marine environment, it quickly reacted with the abundant dissolved iron in the mineral – rich seas. The newly formed iron oxides (rust) were insoluble and so settled to the bottom of the oceans.

4. DP2- Discuss the roles of precipitation and photosynthesis in the removal of carbon dioxide from the early atmosphere • At first, the sedimentation was slowly deposited, however as the number of photosynthetic organisms exploded , so did the amount of oxygen produced. This resulted in layers many of kilometres thick being deposited over hundreds of millions of years. • Most of the world’s iron ore deposits are the remnants of these layers.

5. DP2-Discuss the roles of precipitation and photosynthesis in the removal of carbon dioxide from the early atmosphere • Not until the production of oxygen exceeded its loss by chemical combination in the oceans could it start to accumulate in the atmosphere. This became possible when the levels of dissolved iron in the sea began to be depleted. • The effects of photosynthesis dramatically and permanently altered the composition of the oceans and the atmosphere.

6. Review Questions Identify photosynthetic bacteria as the first organisms to release oxygen into the environment 1) What were the first organisms responsible for releasing oxygen into the environment? 2) Identify the biological process used by these organisms to release oxygen into the atmosphere 3) Identify the role played by the first photosynthetic organisms to appear on the Earth Discuss the role of precipitation and photosynthesis in the removal of carbon dioxide from the early atmosphere 4) Describe one way in which carbon dioxide was removed from the earth’s early atmosphere 5) Discuss the role of precipitation and photosynthesis in the removal of carbon dioxide from the early atmosphere Predict and explain the differences in composition of the oceans before and after the evolution of photosynthesis 6) Predict two changes in the composition of the oceans after the evolution of photosynthesis 7) Explain why these changes occurred

7. DP3-Predict and explain the differences in composition of the oceans before and after the evolution of photosynthesis • After the evolution of photosynthesis the oceans were changed dramatically. This included a reduction in the amount of carbon dioxide in the water levels and the resulting production of oxygen. There was also a decrease in iron as it reacted with the oxygen to form iron oxides which deposited on the ocean floor