2005 HSC Notes fromthe Marking Centre

Earth and Environmental Science

STANSW Meet the Markers

David Tweed, Penrith Anglican College d.tweed@pac.nsw.edu.au

Fiona Branch, Sydney Grammar, fhb@sydgram.nsw.edu.au

General Comments

• 1131candidates attempted the Earth and Environmental Science examination.

• The most popular electives were Introduced Species and the Australian Environment (76%) and Oceanography (10%).

Content

• knowledge, understanding and skills developed through the study of discrete sections should accumulate to a more comprehensive understanding than may be described in each section separately

• It is important to understand that the Preliminary HSC course is assumed knowledge for the HSC course.

Skills 9.1

• at least one question in Section 1 Part B focused on the mandatory skills content in Module 9.1. Candidates who had actively planned and performed practical experiences clearly demonstrated a deeper knowledge and understanding of the content described in this module.

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. This may include the use of dot points, diagrams and/or tables, and avoids internal contradictions. This isparticularly so in holistic questions which need to be logical and well structured.

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.)

Scaling of EES

http://www.uac.edu.au/pubs/pdf/2005-Table-A3.pdf

b) Oceanic crust is denser and thinner than continental crust.

c) The collision of two plates results in Compressive Forces that cause faulting, folding and metamorphism of rocks

17 a) Pyroclastic flow, Lahar.

b) Sumatra is Located near a subduction zone. The subduction of the indo Australian plate beneath Sumatra causes the production of magma due to partial melting. This magma creates the composite volcanoes like Toba.

18 a) Radon gas meters measure the level of radon gas released from faults. An increase in the level of radon detected could indicate an increase in earthquake activity, and thus prove useful in predicting earthquakes.

b) Current technology has many problems predicting earthquakes. Improved methods would lead to more accurate early warning systems and evacuation plans decreasing the loss of life and the destruction of infrastructure.

19 Heat generated from the base of the mantle circulates in convection currents. The mantle material becomes less dense and rises when heated. The horizontal motion of the convecting mantle results in friction with the plates producing basal drag. This drives the plates in the direction of the convecting currents.DIAGRAM of convection Cell

20(a)

Time DivisionLength of time (Ma)

Proterozoic 1950 Ma

Archean 1300 Ma

Cenozoic 50Ma

Triassic 40 Ma

(b) Precambrian Postcambrian

Soft body parts Development of hard body parts

Simple life forms More complex life forms

Generally less predation More predation

Vulnerable to predation More protective body parts less vulnerable to predation

21(a) BIF’s are sedimentary rocks formed of alternating layers of

Iron oxide rich (indicating increasing oxygen levels) and iron oxide poor (indicating low oxygen concentration) high silicate sediments. They indicate fluctuating levels of O2 in the aquatic environment, produced by cyanobacteria.

The O2 released, reacted with the Fe2+ dissolved in the oceans to form FeO which settled on the bottom of the aquatic environment. As the cyanobacteria populations varied so to did the oxygen levels and the consequent FeO levels in the Sediment

(b) The media report is unreliable as the Cretaceous environment was highly Oxygenated supporting a wide variety of life forms that used respiration. All the free Fe2+ had precipitated out of the ocean by this stage allowing oxygen to enter the atmosphere, form ozone and allow terrestrial ecosystems to develop.

Roots/Rhizoids – would only need small root hairs as they would be mainly used for attachment to some substrate in a swampy environment.a more extensive root system would be required for the absorption of water and nutrients and for anchorage of the plant.

Stem – Plant stem in water is buoyed up by the water therefore does not require much structural material.In a terrestrial environment the stem would need to be strengthened by lignin/cellulose for support.

Reproduction - Sporangia would release spores into a watery environment.on land, seeds would be needed prevent dessication

23 (a) Oxygen is composed of 2 atoms O2

Ozone is a molecule combining 3 oxygen atoms O3

(b) The general trend is a decline in Ozone over 45 yearsThere are many fluctuations over this timeThe most rapid decline is between 1980 and 1990. The levels seem to be stabilising between 1995 and 2000

(c) Montreal protocol – early signs show success as ozone depletion stabilised.Banning of ozone depleting substances (eg CFC Halides, Methyl bromide) used in aerosols, refrigerants, extinguishers.Impact on society increased awareness, finding alternatives impacts upon industry, decrease in skin cancer in the long term.Impact on the environment- Increasing levels of ozone once again, reduction in level of UV reaching the earth. Some replacements for CFCs are greenhouse gases creating/enhancing other problems.

Sewage treatment is a current method. It involves the primary, secondary and tertiary stages of treatment as detailed below.This is an effective method as it removes all solid wastes, kills bacteria, removes organic material and soluble nutrients. It prevents the growth of algal blooms and eutrophication and is and environmentally friendly process. This along with the fact that the recycled water can be returned to town catchment water supplies used to drink, irrigate or maintain environmental flows makes it an effective method.

Lquid waste(sewage)

Filtration (PRIMARY)Grates mesh filters are used to filter out solid larger material as liquid waste passes through

Sedimentation (PRIMARY)Liquid waste is placed in tankes and settles. Denser materials accumulate at the bottom known as sludge. Liquid is decanted from the sludge

Bacterial Decomposition Trickled over rocks coated with bacteria. Organic material is removed.SECONDARY

Aeration Churning of remaining wastes helps remove organic materialSECONDARY

Nutrient RemovalPonds lagoons are used for algae to absorb the soluble nutrientsSterilisation of waste by UVAddition of chlorine to remove bacteria

Recycled Water Appropriate use of drinking irrigation agriculture environmental flows catchments

Filtered waste sludge to landfill and fertiliser

25An environmental flow introduces released dam water back into the environment in cycles.

This is important as the introduction of water stimulates breeding /dispersal of some species and ensures biodiversity is maintained.

It allows the dispersal of organic material over flood plains which contributes to the soils fertility and maintains plant diversity and health.

26 Soils in the west are vastly older than soils in the east. Soils in the west are also nutrient poor ( less fertile ) compared to the soils in the east. The age of soils affects the amount of weathering and erosion that they have undergone. WA soils have undergone millions of years of leaching depleting them of any nutrients they may have had.

Soils in eastern Australia have not gone through as much leaching so have still retained many of their original nutrients.

Recent volcanic activity in the east has also lead to the formation and replenishment of basalt derived nutrient rich soil. A lack of volcanic activity of any recency in the west means there has been no replenishment of nutrients via weathering and erosion of basalt.

27i) A table was used to present the data. It had three columns for name, type and description of the indigenous and non indigenous species in the area

(ii) This investigation was best undertaken by a team as we needed a wider knowledge of introduced species for identification. More people gave us a wider knowledge and enabled us to finish the job in a shorter time

(a)(i) Graph Q27b Abundance of species over time

(ii) the number of species 1 increases rapidly from 30July to 5 August2002 indicating that it was well adapted to the environment. Between 5 August 2002 and 17 February 2003 the number of species declined rapidly due to the a drought as they were not adapted to the change. After that the species that survived started to increase slowly.Species 2 declined throughout the whole range but were less affected by the drought, as they were better adapted to these conditions.

Salvinia molesta is a pond weed that was introduced in the 1950’s and escaped from fish ponds and entered waterways Recently there has been an outbreak of this plant in the Hawkesbury Nepean river system. Salvinia lives in waterways with high nutrient levels resulting from agricultural runoff It’s high reproductive capacity means that the plant can double it’s size in two days covering an area of 100km2 in just three months. Salvinia floats on the surface of the water preventing light from penetrating , and thus killing aquatic plants, reducing aquatic Oxygen and leading to eutrophication.A number of strategies have been implemented to control this species. A biological control has been released to naturally control the plant growth. A brazilian weevil was released to burrow into the salvinia, allowing bacterial spores to enter the plant and kill it. This method is effective on large outbreaks as it isn’t labour intensive and is cost effectiveonce it has been trialled and released.This trial process is however expensive and timely. The weevil doesn’t survive in cooler areas. So despite it’s success it has it’s limitations as a means for control. Herbicides have also been used to effectively control large populations of salvinia however this process is expensive as it is labour intensive and it also adversely affects non target species. Salvinia’s high reproductive capacity means that if only a few plants excape the spraying then it could quickly repopulate the area. Methods used to control the spread of Salvinia are effective in some ways but ineffective in others. An integrated approach may be the best option to control salvinia and rehabilitate the ecosystem

d (i) European farmers introduced plants for agriculture eg fruit trees because they had a better knowledge of farming methods of crops cultivated in their homeland and preferred to eat European food types.

(ii) The garden in photo 1 has involved the removal of native species and their replacement with lots of introduced species. Abiotic characteristics that have been altered include:-Pine trees drop needles and increase the acidity of the soilUse of excess water on the garden or plants with shallower roots may cause the watertable to rise and create salinity problems.Less sunlight reaching the soil due to more dense vegetation compared to native garden.

(iii) The garden in photo 1 will start to die off since the plants do not have special adaptations to prevent water loss or conserve water. For example the plants possess shallow roots that do not allow them to suck up water if the watertable drops severely during the drought or they have large thick leaves or lots of large stomates that cause them to loose water quickly through their leaves. The garden in photo2 will survive since native plants are well adapted to dry Australian conditions. They possess smaller leaves with waxy coatings or the trees possess deep roots that will enable them to suck up water from a lowered water table.