2008 HSC Notes from the Marking Centre Earth and Environmental Science

1. STANSW Meet the Markers 2008 HSC Notes fromthe Marking CentreEarth and Environmental Science David Tweed, Penrith Anglican College d.tweed@pac.nsw.edu.au

2. General Comments • 1240 candidates attempted the Earth and Environmental Science examination. • The most popular electives were Introduced Species and the Australian Environment (78%) and Oceanography (8%).

3. Content • examiners may write questions that address the syllabus outcomes in a manner that requires candidates to respond by integrating their knowledge, understanding and skills developed through studying the course, including the Prescribed Focus Areas. • It is important to understand that the Preliminary HSC course is assumed knowledge for the HSC course.

4. Depth of treatment • Candidates need to be reminded that the answer space provided and the marks allocated are guides to the maximum length of response required. • Candidates should use examination time to analyse the question and plan responses carefully, working within that framework to produce clear and concise responses. • dot points, • diagrams and/or • tables, • holistic questions which need to be logical and well structured. • confused the terms and concepts of • global warming and ozone depletion • the Cambrian Explosion with a mass extinction event.

5. Better Responses • Better responses indicate that candidates are following the instructions provided on the examination paper. In these responses, candidates: • show all working where required by the question • do not repeat the question as part of the response • look at the structure of the whole question and note that in some questions the parts follow from each other, ie responses in part (a) lead to the required response in part (b) etc • use appropriate equipment, for example, pencils and a ruler to draw diagrams and graphs. (A clear plastic ruler would aid candidates to plot points that are further from the axes and rule straight lines of best fit.)

6. Option Answers • In Section II, the option question is divided into a number of parts. Candidates should clearly label each part of the question when writing in their answer booklets. • In part (e) of the 2008 option questions, the best responses presented ideas coherently and included the correct use of scientific principles and ideas. • Many candidates wrote a lot of information that was not relevant to the question. • Some responses showed evidence of rote learning an anticipated answer. These responses did not address the syllabus content and/or outcomes being assessed and hence did not score full marks. • Candidates are required to attempt one question only in Section II, but some candidates responded to more than one option question. • Candidates are strongly advised to answer the option they have studied in class.

7. 2008 Scaling of EES http://www.uac.edu.au/pubs/pdf/2008_table_A3.pdf

23. Zone C

27. Subduction Zone - causing deep ocean trenches ie: ocean-cont convergence Mid-Ocean Ridge Non-Explosive/ Passive Explosive

29. Large scale volcanic eruptions have many long and short term effects, especially on the. climate. In the short-term, rainfall can increase due to fine ash particles. There may also be a decrease in temperature due to ash particles blocking sunlight. However, the long term effects can be much more detrimental. The combination of ash and sulphur dioxide aerosols reduces sunlight penetration for extended periods of time, causing a possible global cooling effect. Other gases such as may create acid rain impacting on water quality and vegetation.

33. Waxy Cuticles, Root Systems The exposure to air resulted in the risk of plants drying out so plants with an adaptation like a waxy cuticle on the surface (to prevent fluid loss and retain moisture) ,had an advantage for survival in a terrestrial environment.

36. (a) A sedimentary deposit consisting of Alternating Layers of iron rich and iron poor sediment formed in the Archaean Eon (b) During the Archaean Eon there was no O2 in the Atmosphere (anoxic) however the levels of O2 begin to rise in the Proterozoic as the formation of the BIFs declines and then ceases. Following this 02 levels continue to increase in both the Atmosphere and the Hydrosphere until they level off more recently. (c) Photosynthetic organisms like Cyanobacteria in the ocean were photosynthesising producing O2 as a waste product. The ocean at this time had high levels of Iron salts possibly from fumaroles or weathering and erosion. The O2 reacted with the Iron Salts dissolved in the ocean and formed Iron Oxide which sinks to the ocean floor to create an iron rich layer. Once the Iron Oxide was deposited the oxygen may have risen to toxic levels in the ocean which killed most of the cyanobacteria. This would then mean that cyanobacteria and Iron salts would take a while to increase thus making an iron poor layer with natural sedimentation. When the Iron levels and the oxygen levels were high enough again, the cycle of iron oxide deposition would begin again.

37. Approximately 3.8 billion years ago in the Archaean Eon Living things absorb more of the stable isotope carbon 12 than the stable isotope carbon 13 from the environment during normal life processes. If an ancient deposit has a higher ratio of C 12:C 13 than occurs in the environment then it may indicate the presence ofliving things at that time. One example of this is the graphite crystals found in highly metamorphosed sediments in Isua, Greenland. The rocks, if containing ratios indicative of life, can be dated using normal techniques to determine the age of the deposit.

39. One hypothesis for the extinction of the megafauna is the arrival of people on the Australian continent. Evidence suggests that the arrival of people and the extinction of the megafauna overlap from 50000 to 42000 years before the present. It has been argued by scientists (Flannery, Johnson etc) that because megafauna were a good source of meat and had a slow reproductive rate then it was possible for the first Australians to eventually hunt them to extinction over a few generations as their population continued to decline. Another Hypothesis is that of climate change. As the Australian continent moved northward from Antarctica the climate would have shifted from cool and wet to cool and dry to finally hot and dry. The lush forests of Gondwana would have changed to the Arid saltbush plains of most of Australia today. With ihcreased drying many Megafauna would have found themselves isolated around inland lakes that continued to dry out. Eventually the lake would form a salt pan and the ,:niegafauna would have had to migrate or die out. If it was too far the species would have died of thirst or starvation along the way. Geniornis was a large flightless bird for which fossils have been found at Lake Mungo, a fossil lake in Western NSW. Both hypotheses are plausible but the hunting hypothesis has the strongest support.

41. a) Plant deep rooted native plants in order to lower the water table. b) Water tables rise because of land clearing and/or inefficient irrigation. This mobilizes salt within bedrock and brings it to the surface. By planting deep rooted plants which take in a lot of the infiltrating water, water tables do not rise, thus prevent upward salt movement.

45. i) Anywhere on the impermeable shale. • ii) The impermeable horizontally bedded shale will minimize the leakage of leachate. X

47. Australia is a very old continent. Its great age means that is has been weathered and eroded extensively which has resulted in low relief and nutrient depleted soil. The low relief can also been attributed to the lack of recent tectonic processes such as mountain building or volcanism. Mountains tend to erode to produce new nutrient enriched soil as do volcanoes. The fact that Australia has missed out on the replenishment of nutrients by these processes means that our soils are thin, nutrient poor and cannot sustain extensive cropping which cause our farms to be very vulnerable to other small environmental changes. Australia's climate is one of harsh contradictions, some parts can be very cold and some very hot. Rainfall is minimal mostly due to the flatness of the continent and lack of orographic rainfall which means Australia's native flora and fauna are very specialized to these conditions. This specialization is enhanced by the fact Australia has been isolated as an island for so long, thus very unique flora and fauna have evolved. Because they are so specialized they can also be exceedingly vulnerable when exposed to changed conditions such as an introduced species or diseases.

50. a i) An introduced species is one that is not indigenous to a particular locality. a ii) Modern quarantine is designed to stop the introduction and spread of new species, disease and pests into the Australian environment. a iii) AQIS X-ray and physically search all luggage/ packages/ cargo coming in from overseas for signs of introduced species a iv) Some forms of organisms, such as bacteria, can live in mud. A tourist may visit an area where the disease originates and walk through the mud. On arrival home the organism will be introduced because of the mud on the shoes. a v) An organism may be introduced for the purpose of food, for example -beef cattle.