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2009 HSC Notes from the Marking Centre – Earth and Environmental Science

Contents

Introduction

This document has been produced for the teachers and candidates of the Stage 6 course in Earth and Environmental Science. It contains comments on candidate responses to the 2009 Higher School Certificate examination, indicating the quality of the responses and highlighting their relative strengths and weaknesses.

This document should be read along with the relevant syllabus, the 2009 Higher School Certificate examination, the marking guidelines and other support documents which have been developed by the Board of Studies to assist in the teaching and learning of Earth and Environmental Science.

General Comments

Teachers and candidates should be aware that examiners may ask 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 focused areas. It is important to understand that the Preliminary course is assumed knowledge for the HSC course.

Candidates need to be aware that the mark allocated to the question and the answer space (where this is provided on the examination paper) are a guide to the length of the required response. A longer response will not in itself lead to higher marks. Writing far beyond the indicated space may reduce the time available for answering other questions.

Candidates need to be familiar with the Board’s Glossary of Key Words which contains some terms commonly used in examination questions. However, candidates should also be aware that not all questions will start with or contain one of the key words from the glossary. Questions such as ‘how?’, ‘why?’ or ‘to what extent?’ may be asked or verbs may be used which are not included in the glossary, such as ‘design’, ‘translate’ or ‘list’.

Teachers and candidates should also be aware that questions may be asked that focus on the mandatory skills content in Module 9.1.

Candidates should use examination time to analyse the question and plan responses carefully, working within that framework to produce clear and concise responses. The response may include the use of dot points, diagrams and/or tables, and planning the response will help to avoid internal contradictions. Holistic responses need to be logical and well structured. There was evidence that some candidates had very poor knowledge of the basic terminology associated with the course.

Stronger 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, eg responses in part (a) lead to the required response in part (b)
  • use appropriate equipment, eg 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.)

In Section II, each option question is divided into a number of parts. Candidates should clearly label each part of the question when writing in their answer booklets.

Candidates are required to attempt one question only in Section II, but some candidates responded to more than one. Candidates are strongly advised to answer the option they have studied in class.

Section I – Core

Part B

Question 16

  1. Better responses identified ‘X’ as a transform fault.
    1. Weaker responses either described the rise of basalt from the mantle or indicated that the whole area had been pushed up by the less dense hot rock beneath the MOR.  In the best responses, candidates put both ideas together as well as describing thermal expansion, the role of density, and identifying shield volcanism as having contributed to the formation of this type of mountain range.

Question 17

  1. Stronger responses described how their chosen technology could predict earthquakes.
  2. The best responses identified the impact and described how the earthquake caused the damage through the motion of waves or the movement of the ground.

Question 18

The best responses addressed the growth of the western part of the continent through cratonisation as well as the role of subduction in the growth of the eastern part of the continent. These responses described subduction and its consequences in detail and identified the formation of new crust linking this to the process. The answers were written in coherent and logical style using scientific terminology. Weaker responses confused convergence and divergence and were too general and lacking in specific detail. Some weaker responses included irrelevant information such as soil fertility, continental stability or erosion/weathering.

Question 19

  1. In the best responses, candidates produced a well-drawn cross-section of an oceanic-oceanic convergent collision. They included and labelled the following features:
    • direction of movement of the plates
    • correct position for the island arc
    • other features – such as trench, subduction zone, earthquakes, melting of subducting oceanic crust, accretionary wedges, convection currents.
    Weaker responses presented diagrams of oceanic-continental convergence or failed to position the island arc on the correct side of the plate convergence. Some weaker responses included unlabelled diagrams.
  2. Stronger responses acknowledged that the results were reliable because the data given was from a variety of scientific instruments, which gave consistently similar results. These responses also recognised that accuracy was due to the use of advanced technology by specialised scientific organisations. Weaker responses did not distinguish between reliability and accuracy, usually addressing only reliability. Those responses that attempted to address accuracy failed to recognise the scientific expertise of the organisation.

Question 20

  1. The best responses identified reduction in abundance and distribution of stromatolites over time. Reduction in abundance was linked to the evolution of competitors and predators. The reduction in distribution of stromatolites to harsh conditions such as highly saline waters was linked to the need to exclude predators and competitors from their habitat. Weaker responses identified the decrease in abundance and distribution without explaining the cause.
  2. The best responses identified early photosynthesising organisms, ie cyanobacteria, as being responsible for the build-up of oxygen in the atmosphere.  They then gave a detailed outline of the steps in the processes of ozone formation from oxygen molecules, with oxygen being split into two atoms by UV radiation, followed by a combination of O2 and oxygen atoms to produce ozone. Weaker responses left out a part of the ozone formation process or wrote in detail about Banded Iron Formations, or only referred to oxygen forming ozone with no attempt to outline the steps involved in the process of ozone formation.

Question 21

  1. The best responses mentioned specific structures like a vascular system (xylem and phloem) to transport food and nutrients, waxy cuticles or stomata in relation to preventing water loss.
  2. Good responses recognised that a reptile’s ability to tolerate drier environmental conditions is the main determinant of their relative success over amphibians in the terrestrial environment. The best responses outlined an environmental feature in the terrestrial realm and at least one feature that illustrated this tolerance, such as scaly, waterproof skin, internal reproduction or a waterproof leathery-shelled egg. These features were contrasted with at least one feature of an amphibian.

Question 22

  1. The best responses clearly outlined the function of the feature in part (a) and linked it with greater survival rates, access to new food sources or access to new habitats.

Question 23

Good responses described an appropriate pest management strategy that is an alternative to pesticide use and successfully related the strategy to its intended effect on the pest, whether it was to kill or repel. Well-structured responses made a judgement on the overall effectiveness of the management strategy. In the best responses, candidates compared the strategy to the issues related to pesticide use such as effects on non-target species, bioaccumulation or biomagnification.

Question 24

  1. In the best responses, candidates identified sedimentation or a related process linked to gravity or the settling out of matter.
  2. In the best responses, candidates were able to relate disinfection or more specific processes such as UV treatment or chlorination to this stage of sewage treatment. The best responses also outlined the process of disinfection by using UV light, ozone or chlorination to kill bacteria and provided the reasons why this was necessary.

Question 25

In the stronger responses, candidates named their strategies rather than giving a description of them.  They also directly stated the impact of their chosen strategy on the site. Weaker responses identified strategies that would create new land uses rather than rehabilitate the site, eg landfill or housing development. Stronger responses provided justifications for their chosen strategies rather than general or vague statements such as ‘to help the environment’.

Question 26

  1. The stronger responses identified that higher moisture levels correlated directly with lower sheep numbers. Weaker responses sometimes drew conclusions that were not based on or backed up by the data.
  2. Stronger responses stated Graph A showed that increase numbers of sheep correlated with decreased soil moisture, and Graph B showed that decreased soil moisture correlated with increased erosion, and finally recommended a suitable strategy to retain soil moisture levels, thereby minimising erosion. Suitable strategies included reduced stocking rates, paddock rotation and irrigation.

Question 27

In the stronger responses, candidates demonstrated a holistic approach, relating specific features of the environment and specific unsustainable resource use to identified extinction events. These responses also referred to the arrival of both Aboriginal and non-Aboriginal humans to Australia. These responses also showed clear cause-and-effect relationships, linking habitat disturbance to the disruption of food webs, ecosystems and ultimately to extinctions in a clear, logical and sequential manner.

Weaker responses demonstrated confusion between extinction of whole species and the death of organisms. These responses did not demonstrate clear links between causes and effects especially in relating extinctions with features of the Australian environment. Weaker responses also demonstrated a number of misconceptions, particularly in relation to the timescales over which these extinctions occurred, ie over terms of thousands of years rather than millions of years.

In weaker responses, there was confusion between unsustainable use of fossil fuels, greenhouse gas emissions and ozone destruction. Weaker responses also concentrated on one or two particular points from the syllabus rather than taking a holistic approach.

Section II – Options

Question 28

    1. The strongest responses named an introduced plant that had become a pest in Australia at either national, state, regional or local council level. Weaker responses either named an animal or named an introduced plant that was not a recognised pest at any level.
    2. The strongest responses clearly identified the reason the plant was introduced to Australia. Weaker responses identified a use of the plant following its introduction or used very general terms, eg ‘accidently’.
    3. The strongest responses used a well-structured answer and recognised the main features of the plant which allowed it to disperse within the Australian environment. The weaker responses did not provide the main features. Instead they identified a general criteria, eg ‘suited to Australian conditions’.
    4. The strongest responses named the control method and specified the type used, eg biological control via cactoblastis moth. The weaker responses named only a control method, eg biological control.
    1. The stronger responses clearly identified a valid potential risk of the program.
    2. The stronger responses made a valid judgement on the effectiveness of the program.  Trends in the data were clearly identified and linked to the judgement and criteria used for the judgement were defined.  They also included comments about the inadequacy of the data provided and the inferences that would have to be made to provide a judgement on the effectiveness of the program. The weaker responses did not provide a judgement, did not identify trends in the data or did not link their judgement to sound criteria.
    1. The stronger responses clearly provided the main features of two criteria used to determine the conditions under which an organism can be used for biological control. The weaker responses either listed two criteria without giving their main features or answered in question form.
    2. The best responses constructed a table that clearly outlined the similarities and/or differences between the two types of biological control. The weaker responses either described each biological control method without clearly comparing them, discussing their effectiveness, or mistakenly linked the two control methods, suggesting sterilised males were given the parasites.
    1. Weaker responses did not understand the term ‘independent variable’, confusing it with ‘controlled variable’.
    2. Stronger responses included a line of best fit and labelled their axes correctly, assigning correct units and using a linear scale. Poorer responses drew a column graph, or extended the line beyond the data to the origin.

      Some weaker responses accurately plotted the points but did not join the points or draw a line of best fit.

  1. Many candidates gave at least one point of reference from the graph. The stronger responses clearly outlined the trend with points of reference.
  2. Stronger responses identified more than two introduced species, clearly demonstrated an understanding of biotic and abiotic components of the environment and scientifically linked the impact on these components of the introduction of the new species.

    Weaker responses did not demonstrate an understanding of components as being biotic or abiotic or did not express their answers in scientific terms, eg ‘rabbits cause native species to die’ rather than ‘rabbits out-compete native species leading to a loss of biodiversity’.

Question 29

    1. In the stronger responses, candidates were specific in their locality.
    2. In the strongest responses, candidates were familiar with the term ‘element’ as opposed to compounds or mixtures.
    3. Stronger responses included the use of the term ‘fraction(s)’.
    4. Stronger responses named carbon particulates while poorer responses chose water vapour.
    1. Stronger responses included a money/cost effect.
    2. Good responses correctly identified one other energy source (renewable alternative) and provided the benefit of the named source. Stronger responses provided information supporting their choice.
    1. Stronger responses provided a basic description of catalytic cracking.
    2. Stronger responses outlined both the changes to the organic material and the physical conditions that caused these changes for each stage.
    1. Weaker responses demonstrated confusion when determining dependent and independent variables.
    2. Stronger responses connected the points with a line and put the independent variable on the x-axis.
  1. Stronger responses used specific information from the graph, quoting data points to demonstrate their understanding.  Stronger responses communicated that there were two different rock types.  
  2. Better responses identified the components and clearly demonstrated the link between geology and exploration techniques.

Question 30

    1. Better responses were specific when they named ‘landmark decisions’ that have affected mining in Australia.
    2. Stronger responses resulted from reading the whole question and relating the answer from (a) (i) to the exploitation of a mineral deposit. Weaker responses referred to state government decisions rather than those decided in the High Court.
    3. Weaker responses failed to understand there is a difference between renewable and recyclable.
    1. Stronger responses often supported the answer with calculations.
    2. Stronger responses identified some features of the model of mineral genesis of a named resource and province.  Weaker responses lacked detail in their description of genesis or did not identify the province.
    1. Stronger responses referred to a specific ore deposit and described examples of infrastructure that were in place or needed to be put in place.  They also outlined the impacts of these on the feasibility of mining the deposit.
    1. Weaker responses demonstrated confusion when determining dependent and independent variables.
    2. Stronger responses included fully labelled X and Y axes including units. Linear scales were used. Points were plotted and joined by a line of best fit clearly drawn. Weaker responses tended to lack these details.
  1. Stronger responses described a trend and used numerical evidence.
  2. Stronger responses made a judgement or evaluation of mining sustainability and supported this by correctly mentioning an environmental impact including examples and/or a rehabilitation method used to combat the impact including an example.  A limitation to the resource being mined was also included.

Question 31

    1. Weaker responses quoted incorrect values.
  1. Stronger responses included a consequence of sewage disposal by ocean currents and made reference to the diagram.  Weaker responses made superficial reference to general terms like ‘pollutants’ only.
  2. Stronger responses clearly linked the increased understanding of an aspect of the ocean with a change in use of a specific resource.
    1. Stronger responses clearly stated how the chosen technology worked and identified the information about the oceans that could be obtained from it.
    2. Stronger responses made specific reference to the data that could be obtained by new technologies and made a judgement of the potential benefits of this new data.  Weaker responses contained generalisations.
    1. Stronger responses joined the plotted points or used a line of best fit and did not extend the graph beyond the data provided.  They used linear scale and units and placed the independent variable on the x-axis.  Weaker responses omitted some of these requirements.
  3. Stronger responses provided links between physical conditions and distribution of marine communities and sediments. They often used light differences at the surface and great depth (>3km) and pressure differences affecting sediment deposition or solubility as part of their analysis.

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