Past papers part 1

Question 1

Why are some scientists investigating the current trend of increasing atmospheric CO2 when Earth’s history has shown the planet has undergone several periods of increasing levels of atmospheric CO2?

Answer 1

There have been periods through time when atmospheric CO2 concentrations have increased. However, on such occasions, the increases have been slow, spanning thousands of years. These increases were usually caused by natural phenomena, such as volcanic eruptions, respiration and asteroid bombardment. On the other hand, the current trend of increasing atmospheric CO2 is much faster, and on a greater magnitude. Although natural processes still contribute to the increase, other carbon sources such as vehicles, livestock and increasing population also contribute to this increase of CO2. There has also been deforestation, which means a removal of carbon sinks.
Hence, the difference between past trends and current trends is the increase in magnitude of CO2, the rate of increase and the increase of carbon source with a simultaneous decrease of carbon sinks. Therefore, scientists are investigating these trends to observe the effect on ecosystems and the planet.

Question 2

Explain how oceans become acidified

Answer 2

CO2 from the atmosphere normally dissolves in the ocean. Some of this CO2 reacts with water to make carbonic acid, which is acidic. When there is extra CO2 in the atmosphere, more will dissolve and react and more carbonic acid will be produced and thus the oceans will become more acidified.

Question 3

Describe one effect of ocean acidification

Answer 3

The more acidic the ocean becomes, the more corrosive it becomes and as such, organisms that make their shells out of carbonate minerals will be negatively impacted, since carbonates dissolve in acidic conditions.

Question 4

How can aboriginal art be used as evidence of the changing biodiversity of Australia?

Answer 4

Aboriginal art is a record of the animals and plants seen by the first Australians at the time that the art was done. Hence, the art gives the record of biodiversity seen at specific locations through time, as rock art can be dated to give an absolute date to the presence of the organisms pictured. This can be analysed for changes through time.

Question 5

Explain how scientists can interpret past environments from the study of sedimentary rocks. (changing isotope ratios)

Answer 5

Fossil analysis can allow you to deduce marine and/or aquatic environments based on the type of fossils found. An example is the presence of coral fossils indicating shallow marine conditions. Further isotopic analysis of the rationing of O16 to O18 planktonic fossil shells can yield information about the global temperature. For example, the more O16 present, the warmer the temperature was, as usually the O16 is locked up in glaciers and ice and only released when these melt. The plankton that incorporate this O16 in their shells can become temperature indicators.

Question 6

Assess the use of ONE geo-engineering strategy in mitigating global temperature increases

Answer 6

Carbon capture and sequestration allows CO2 to be extracted from industrial processes and forced into underground fluids where it is stored. This means the CO2 is held underground instead of released into the atmosphere. This subsequently means it is not increasing the atmospheric concentration of CO2 and thus not contributing to a rise in global temperature. This technique is effective in theory but is still largely experimental and very site specific so may not be utilised enough to make a significant impact.

Question 7

Explain how scientists can interpret past environments from the study of sedimentary rocks. (geologically)

Answer 7

Sedimentary rocks contain structures that reflect the climates in which they form. A common structure is cross-bedding, which forms in dunes and is produced by flowing air or water. Sand dunes on land lead to rocks with large cross beds and characteristic fine sand compositions. They are often iron-stained, reflecting the arid environments in which they form. Cross-beds are common in river-deposited sandstones and indicate the speed of the water moving the sediment. Large sets of cross beds reflect the movement of high volumes of water, and the resulting rocks, as part of a sequence, can be used to interpret the environment and climate in which they formed. Rocks with striations could be a result of glacial ice moving over the rock surface, reflecting a time when the climate was cold and glaciers were present.