Planet Earth and its Environment- FA4

YR 11 EARTH AND ENVIRONMENTAL SCIENCE

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

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.

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.

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.

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

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