EVS315109 - Enviromental Science - Assessment Report 2013 · Enviromental Science Course Code: EVS315109 2013 Assessment Report Tasmanian’Qualifications’Authority’ Page1’of’20’

Enviromental Science Course Code: EVS315109

2013 Assessment Report

Tasmanian Qualifications Authority Page 1 of 20

GENERAL COMMENTS EXAMINER’S COMMENTS The final examination paper was generally well received by both candidates and teachers. There was an absence of questions that required longer answers that suit many candidates. The majority of candidates were successful in Part 1 with only 12% not being successful. Part 2 showed an improvement from previous years with only 11% not being successful. Part 3 provided a good opportunity for some candidates to demonstrate the extent of their understanding of Criterion 6, although 12% were not successful. Part 4 provided the greatest challenge for candidates with 33% not achieving 14 marks. Only 9% of candidates were not successful in Part 5 but then only 9% achieved an A rating. There were seven graphs/charts to analyse and interpret in this section. Many of the last pages were left blank indicating that candidates ran out of time to complete Part 5. There are two different comments to make about the use of the Information Booklet provided with the exam Firstly, many candidates do not use it in their answers at all, and therefore score zero and miss out on achieving minimal marks. Secondly, answering questions by only copying definitions from the Information Booklet and not applying the information to the particular question does not display sufficient understanding and again will only score minimal marks. It is highly recommended that candidates become thoroughly familiar with the Information Booklet and use it in the examination as the memory trigger it is meant to be. Finally, a common problem is failing to address all parts of a question which prevents candidates achieving full marks for their answers. WRITTEN EXAMINATION The following section specifically comments on candidates’ performance. Marking examiners offer suggested answers to each question, followed by specific comment on aspects such as how the question was assessed, where candidates gained or lost marks, where they had difficulty in interpreting the question, or where candidates failed to comprehend what was required to successfully answer the question. The suggested answers are by no means prescriptive. Candidates providing different but valid answers were rewarded accordingly as noted by the examiners. Comments are written in italics for speedy identification.


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SUGGESTED ANSWERS AND COMMENTS Part 1 -‐ Criterion 2 (Scientific Method) Question 1 a) ‘Predatory snails are in competition with sea stars for food resources’

b) Salinity, dissolved oxygen, pH, light, turbidity, wind, temperature with an appropriate instrument for

measuring the abiotic factor mentioned, eg. Universal indicator, thermometer, D.O. meter, light metre

c) Line transect from low to high tide mark along the rocky shore. This could be a belt transect with all of the organisms found within a metre of the line identified and counted, or use random sampling with quadrats at specific distances (eg 5m) along the transect. This information can be used to count/identify of all organisms in the area. Observations of organisms, research and/or dissection of organisms to examine gut content for food sources.

d) Seasonal fluctuations in populations can be observed and more accurate information on when organisms are present/migratory can be gathered. More detailed information on the timing of such changes can be gathered and a fuller picture of the food web interactions gained.

Comments a) Many candidates were not able to form an hypothesis, which was very disappointing. Many wrote

about the possible impact of the snail competing with the sea star for limpets/mussels, but did not form an hypothesis, thus, received zero marks. For three marks, the candidates needed to include a dependent variable, independent variable and form a succinct hypothesis that explained the observations.

b) Most candidates answered this section well, identifying two appropriate abiotic factors to measure in the area. Most were also able to supply an appropriate instrument for measuring each factor. 2 factors and 2 appropriate measurement devices were needed for full marks.

c) Many candidates named, but did not describe with enough detail, the methods which could be used to collect data on the rocky shore. Line transects with quadrants, or belt transects were the most common responses, with identification of the number and type of organisms present. Examination of gut content to determine feeding relationships was also acceptable, as was observations of the organisms feeding/present on the rocky shore. No marks were awarded for ‘capture-‐mark-‐recapture’ responses as this technique is more focussed on estimating populations rather than establishing food webs and feeding interactions between organisms.

d) Many candidates received partial marks for this question as they simply did not explain why monthly sampling was better. Some candidates mentioned hibernation/migratory species and some even mentioned being able to ‘see climate change’. Links between seasonal fluctuations, seeing timing of the changes, abiotic factors and the subsequent impact on organisms escaped most candidates.


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Question 2 Factors; large sample size, controlled variables, replicas, repetition, appropriate duration of experiment, use of a control. Depending on the factor stated, there were many answers which could have been supplied. For example; Sample size; a large number of plates are used in each batch in the experiment. This is to ensure enough data with which to draw valid conclusions from all samples used. A control is present; This is to form a basis of comparison with data from experimental groups and to establish that any difference in results is from the independent variable. Comments Generally, this question was poorly interpreted by candidates. Many candidates failed to read the question correctly and specifically gave examples of in/dependent variables, or supplied three controlled variables specifically for this experiment, rather than give three factors which ensure reliability in any experiment, as they were asked to do. If candidates supplied three controlled variables for this specific experiment, they received a maximum for 2 marks only. Many candidates did not explain how the factor was important to ensuring reliability. Question 3 a) This is a control group; it is used as comparison against the experimental groups so that any

difference can be attributed to the independent variable

b) To ensure they were as similar as possible genetically; eliminate uncontrolled variables/use as a controlled variable

c) Sample size, range of temperatures for the independent variable, controlled laboratory experiment, replicating natural conditions in a controlled environment (or similar as long as it wasn’t mentioning the need for a control or a controlled variable with seeds from the same plant) with a brief explanation of why it was a good aspect of experimental design.

d) Several possible responses due to the open-‐ended nature of the question. For example;

• The time seeds were exposed to the smoke. The seeds were only exposed to 30 minutes of smoke, whereas they were exposed to a range of temperatures. More useful data examining the effect of this variable could have been gathered if the time of ‘smoking’ was varied, like the range of the temperature treatments.

• The use of a hooded BBQ to smoke the seeds. This apparatus in no way would replicate the

conditions that seeds are normally exposed to in a fire; there is also the risk they may be exposed to some rise in temperature in the BBQ from the burning bark, which may give questionable data as two variables were tested at once. Cooled smoke from other apparatus should have been used to negate any effects of increasing the temperature.

e) The data is from two different experiments with different independent variables, so cannot easily be

shown on the same axes. The data is also different (continuous/discontinuous) and requires a different type of graph (bar vs line graph).


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Comments a) Most candidates were able to identify the non-‐treatment group as a control and that it is used a

comparison with the experimental groups to see the effect of the independent variable. Many did not receive full marks as they could not state fully the purpose of the control.

b) Most candidates were able to identify this as a controlled variable/to reduce uncontrolled variables by having the seeds as similar as possible to reduce variation between seeds which may affect the reliability of the results.

c) This question was answered well by most candidates. There were several possible answers that were awarded marks in this question as long as it did not refer to ‘control group’ or ‘including controlled variables’ as candidates were instructed not to refer to these as instructed in the stem of the question. Answers such as sample size, range of temperatures for the independent variable, controlled laboratory experiment, replicating natural conditions in a controlled environment with a brief explanation of why it was a good aspect of experimental design.

d) Most candidates attempted this question, but few received full marks as they did not outline a suitable/practical method by which the method could be improved, or identified two weaknesses without outlining a method for improving the investigation.

e) This question was very poorly answered by most candidates and very few received full marks for their response. Most candidates could identify there were differences in the treatment/results, but could not explain why the data needed two separate graphs. Most focussed on the difference in the treatment (5 groups in the temperature treatment vs one group in the smoke treatment) rather than on differences in the nature of the data (continuous/discontinuous) obtained. There was information on the sheet that could have assisted them to answer this correctly.

Question 4 a) i) Soil nitrogen levels

ii) Abundance of leguminous plants

b) The candidate could vary the level of nitrogen-‐based fertilizer in the soil/growth medium from 0 – 10 ppm.

c) ‘Measure the biomass or the dry weight of the clover plants produced after a suitable growth period’ (2 full marks). ‘Area, volume or density of the clover plants’ was awarded 1 mark. ‘Counting’ was awarded half a mark.

d) Find pasture that has been heavily cropped and contains various areas of soil nitrogen (or fertilize to vary the soil nitrogen levels). Fence these areas/large plots off to stop grazing by animals. Plant a large number of clover plants (20-‐100) in each plot. Ensure all other variables are kept constant. After a season (3-‐6 months), weigh the mass of the clover produced in each plot, average and compare.


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e) Clover are leguminous (make their own nitrogen/rhizobium in root nodules), thus negating the need for nitrogenous fertilizer (1 mark). This may only apply to clover, not all leguminous plants. (half mark). Other soil nutrients/abiotic factors could be causing the change in plant abundance. (half mark).

Comments a) Most candidates were correctly able to identify the in/dependent variables. Some candidates

confused them and thus had an error that carried into parts (b) and (c), losing further marks. Some candidates merely wrote ‘leguminous plants’, rather than ‘abundance of leguminous plants’ and were penalised half a mark.

b) Most candidates answered this part well and long as varying/changing the level of nitrogen in the potting mix/soil was mentioned, received full marks.

c) Most candidates did not write measure the dry weight, or the biomass of the plants produced and

thus, did not receive full marks. Area, volume and density of the plants was awarded half marks, and ‘counting’ was awarded half a mark. Some candidates did not seem to know what ‘abundance’ meant, and many seemed not to know that clover is a low, spreading pasture plant, or what type of plant it was at all. ‘Height’ and ‘growth’ were not awarded any marks.

d) Most candidates answered this question fairly well providing enough of a description in their method for full marks. Many candidates who did not receive full marks just did not include enough detail about how this would be conducted in the field. Experiments trialled in labs or greenhouses were awarded no marks as the question specifically asked for a method to be undertaken in the field.

e) Few candidates were awarded full marks for this question; very few seemed to know that, as a legume, clover can fix its own nitrogen from the atmosphere, thus showing their lack of knowledge of some important aspects in the nitrogen cycle. This was even mentioned in the stem of the question, and was overlooked by most candidates. Some did pick up on the fact that any conclusions were only relevant to clover, not all legumes, and were awarded half a mark.


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PART 2 -‐ CRITERION 5 (ECOLOGY)

Question 5 a)

b) Decomposers, bacteria and fungi, breakdown the food chemically and ingest the breakdown

products. In addition, decomposers breakdown organic matter into inorganic matter. Detritivores, earthworms and beetles, ingest dead material.

c) Producers

d) centipedes, spiders and rove beetles

e) At each trophic level only 10% of the energy is passed onto the next trophic level. The other 90% is used in living and ‘lost’ as heat. The higher trophic level therefore only has 10 % of the biomass of the previous one. So the organisms may be bigger because they are predators but they are far less numerous.

Comments a) Many candidates answered this reasonably well although candidates did lose half marks for not

including the dead plant material at the base of the food web, and, they also lost half marks if the energy transfers were not shown by arrows. There was no need to include trophic levels as part of the 3 marks.

b) To gain two marks candidates had to use examples from the food web. Many chose to ignore this. d) For some reason at least 50 % of the candidates stated birds probably because they did not


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recognise that Trophic Level 1 was the dead plant material. e) To gain full marks a candidate needed to mention the biomass of the organisms. Question 6 a) Candidates who stated that Tasmanian Devils are scavengers because they feed on the carcasses

of dead organisms were awarded 1 mark. Several candidates mentioned they were predators and that is why they are "death lover". No marks were awarded for this answer.

b) The relationship to the fox was: predator and competitor. Interspecific competition was also allowed.

c) Abiotic factor-‐ temperature was the main factor stated. Biotic factor-‐ predation or competition from other animals eg. dingoes or poisoned by a cane toad. Several mentioned a predator being the Tasmanian Devil gaining only half marks.

d) Candidates could gain 1 mark by using the information from their information booklet. However, many stated what a habitat was without reference to the Wet Sclerophyll Forest (WSF). Better answers included: use of hollows in trees for birds etc. The definition of ecosystem often was incomplete and often ignored the interaction between abiotic and biotic factors

Comments It was obvious that quite a few candidates did not know the relationships that exist within a food web. Very few candidates achieved full marks for this question. Candidates once again did not refer to the WSF Question 7 a) A Respiration

B Photosynthesis C Consumption/Predation D Combustion

b) The energy available to humans from coal and oil was once light energy trapped by the process of

photosynthesis. Plants and phytoplankton decay, are covered by sediment and converted to coal and oil. This energy has remained locked in the fossil fuels for millions of years. We are effectively using very old solar energy.

c) The carbon cycle is closed to matter because there is a constant amount of matter/carbon.

Candidates also needed to note that in respect to energy it is not a closed system because sunlight is bringing energy to the carbon-‐cycle and heat is lost out into space.


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Comments a) Most candidates answered this reasonably well. b) Answers to this question varied considerably and it was obvious that many candidates had no idea

how coal and oil forms c) Candidates often just stated what a closed and open system is, straight from the information

booklet, without referring to the carbon cycle. Several started to get confused by talking about it being an open system without noting that they were referring to a local system not the entire earth system.

Question 8 a)

i)

ii) J curve

b) It is most likely that the biological control keeps the number constant around some carrying capacity which is probably lower than before. Many candidates thought that the biological control was the plague.


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c)

d) Negative feedback Comments Overall this was poorly answered. Candidates rarely labelled their graphs and some graphs were illegible. For full marks a candidate needed to draw the graph labelling before, during and after on the x axes (time) and the mouse numbers needed to be noted on the y axis. Question 9 a) GPP is the amount of energy produced by the plants by photosynthesis. In this case 15245 + 1247

= 16492kJ. The NPP is how much of this is passed on 1247 kJ. The 15245kJ is lost in respiration.

b) 1078kJ-‐ half marks awarded if no units.

c) Respiration Comments Very few candidates were awarded full marks largely because they did not use data off the diagram.


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PART 3 -‐ CRITERION 6 (HUMAN DEPENDENCE AND IMPACT ON NATURE) Question 10 a) A benefit provided to humans by their environment, eg climate regulation (trees providing a

windbreak) or transport (via a river). b) The ecological footprint is a theoretical measure of the size of the area used by an individual/

country to live. It incorporates the space inhabited and area required to provide resources and absorb wastes. MEDCs have a far bigger footprint than LEDCs due to their technology base, high standard of living and disposable lifestyle. As population increases we run the risk of overexploiting the planet.

Comments a) Many candidates copied the information sheet word for word to answer this question and

therefore could not be awarded half a mark. Full credit was only awarded to those who were able to explain ecosystem services in their own words and provide two detailed examples (eg other than ‘food and water’)

b) Many candidates answered this question with fairly vague descriptions of resource use and pollution without relating it to the key concept of ecological footprints. There is clearly some confusion about the difference between carbon footprints and ecological footprints. Few candidates identified the difference between LEDCs and MEDCs in terms of their footprints although this is specified in the Course Guide. Candidates should be reminded that a question that asks them to discuss an issue can include a range of arguments.

Question 11

a) Greenhouse Effect Ozone Layer Depletion

Name of the predominant gas involved

carbon dioxide or methane or water vapour

CFCs/ chloroflourocarbons or

atmospheric chlorine Does this gas increase or decrease?

Increase Increase

One major consequence for humans

Increased extreme weather events etc

Increased risk of skin cancer

One other environmental consequence

Sea level rise etc Decreased crop productivity

b) Banning the use of CFCs in refrigerators/ reducing CO2 through increased reliance on solar energy/

reduction of CO2 by carpooling etc.


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Comments a) Some leniency was used in marking this due to ambiguity in the question, particularly with regard

to the ‘predominant gas’. There is much confusion among candidates about the difference between stratospheric ozone depletion and tropospheric ozone pollution.

b) Candidates are reminded that even in a state question, a sufficient level of information must be supplied in the response-‐ for example, writing ‘using renewable energy’ is not enough detail as it is not clear which environmental problem is being reduced.

Question 12 a) Increased phosphorous can lead to an algal bloom, which reduces light availability for aquatic

producers. Once the phosphorous is used the algae die and are decomposed. The decomposers use up the dissolved oxygen in the water, causing the death of heterotrophs. The river may become anoxic, smelly and toxic. This process is known as eutrophication.

b) The BOD is a measure of the rate at which oxygen is removed from the ecosystem. A high BOD results in low dissolved oxygen. The mayfly lymph is an indicator species. As they will not be able to survive in low oxygen, their presence indicates that the stream is healthy.

Comments a) Credit was also awarded for algae releasing toxins into the water or coating the gills of fish. Some

candidates answered this as a biomagnification question and were given a small credit for this. Too many candidates did an ‘information dump’ from their information sheets, rather than explaining the process in their own words. Some credit was awarded for this.

b) Most candidates have a good understanding of the use of an indicator species but too many did

not answer the question in terms of BOD and could not gain full marks. A number of candidates are unsure of the concept of BOD, describing the mayfly lymph itself as having a high BOD. This is a situation where the Information Sheet could have been used to benefit the candidate.

Question 13 a) Yes, they are clean and green because they rely on renewable resources (wind and water) and do

not produce any greenhouse gas emissions once established OR no, they are not clean and because their construction uses materials like steel and concrete, with a high embodied energy; hydroelectricity requires the construction of dams which can damage ecosystems; wind turbines can interfere with the routes of migratory birds.

b) Burning coal produces carbon dioxide, which contributes to the greenhouse effect, and sulphur dioxides, which can cause acid rain. Brown coal is more impure than black coal and produces more emissions.


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Comments

a) Any two reasons, sufficiently explained. This question was generally done well, with some candidates gaining partial credit for only supplying one detailed reason, or two without detailed reasons eg ‘the construction and maintenance of the wind farms generates pollution’. A surprising number of candidates described wind and water as ‘natural’ resources, as are coal, oil and uranium, when they presumably meant ‘renewable’ resources. Too many candidates also erroneously stated that once built, hydro and wind power didn’t use energy.

b) This question was poorly answered with only two candidates in the state achieving full marks. Most candidates identified carbon dioxide as an emission and some also identified it as a greenhouse gas. Very few candidates were able to identify any other emissions produced in burning coal. It is obvious that few candidates knew the difference between black and brown coal and most ignored this aspect of the question. For full marks, candidates needed to identify two emissions and their effects, and explain why brown coal was especially bad for the environment.

Many candidates wrote about the environmental problems associated with mining and transporting coal, but as this question was specifically about the burning of coal these were not given credit. Answers about thermal pollution or specific emissions were awarded marks.

Question 14 a) Emissions / the population density is low so there isn’t much automobile traffic / Tasmania’s

windy climate keeps air circulating / few areas of intensive industry to keep emissions down. b) Because our electricity is not generated by coal-‐fired power stations, there are fewer inversion

layers / on a very still day / when there is a bushfire / when people are burning wood fires in winter

Comments a) This question was generally done well. Candidates should remember that an explanation needs to

link cause and effect. b) Considerable leniency was applied in marking this question as the term ‘smog’ was quite

ambiguous. Many candidates interpreted this as asking when smog could form in Tasmania, rather than when it can, and therefore answered in terms of future population growth or development of industry. These answers were given credit although strictly, they were not answering the question asked.

Question 15 a) Because of biomagnification. The pollution enters the food chain and is passed up the food chain

at each stage, because heavy metals can’t be metabolised and excreted. They are increasingly concentrated as 90% of the biomass is lost. Heavy metals can cause lung, heart and nervous disorders


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b) A common is a resource that is owned by no one and used by everyone. Access to commons is unmanaged and tends to result in people exploiting the resource for short term gain. In this case industry would have polluted the river with run off, without regard to the long term degradation.

Comments a) This question provided a good opportunity for some candidates to gain full marks. Most candidates

were able to gain some marks for this question, but full marks were not granted unless they demonstrated some understanding of why the heavy metals increased in concentration (eg the loss of biomass at each trophic level).

b) This question was quite disappointing to mark. Many candidates had little idea of what was meant by a common, in spite of the Tragedy of the Commons being an unambiguous part of the syllabus. For full marks candidates had to demonstrate their understanding of commons and apply specifically to the river.

Question 16 The establishment of plantations through clear felling destroys habitats and has a significant effect on biodiversity. Timber plantations themselves are monocultures, with one species of tree cultivated and competing species actively removed. This reduces plant biodiversity and diversity of the animals that depend on the plant. Soil health in monocultures is also reduced, impacting on biodiversity. Selective logging maintains most habitats and niches, and the understory is intact, so has little impact on biodiversity. However, genetic diversity may be reduced, as the big trees are removed and smaller trees remain. Comments There were many things that candidate could have discussed in their responses and it was surprising to see how many received no marks for this question. The most common error was to discuss selective logging vs plantations in terms of economic benefits of ease of management without addressing biodiversity at all. A significant number of candidates believe that plantations are more biodiverse than a selectively logged forest.


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PART 4 -‐ CRITERION 7 (SUSTAINABILITY) Question 17 a) The Tasmanian Government is concerned about economic sustainability. Tourism is a way of

bringing revenue into the state and creating jobs, and this has a flow on effect in the economy – intragenerational equity.

b) Land clearing for the hotel reduces the local habitat and may affect biodiversity; there may be an

introduction of feral animals and plant diseases and waste from the hotel e.g. sewage may not be a adequately treated and waterways may be polluted.

c) Revenue from these developments could be used for park management and upgrading of walking

tracks. The use of renewable energy, e.g. solar and wind, may mean less environmental effect of power lines coming in.

d) Environmental Impact Assessment e) Cost Benefit Analysis and Risk Assessment Comments a) Poorly answered. Many missed the Government’s objective in the first sentence i.e. the economy.

So those who claimed the government wanted tourists to see how beautiful Tasmania is, or wanted to educate tourists about the environment missed the marks.

b) Also poorly answered because there was no emphasis on ecological sustainability.

c) Same as b)

d) Most were able to get this

e) Same as d) Question 18 a) There is a vision statement for the Tarkine. All the stake holders e.g. community,

environmentalists, miners are consulted and all the resources are mapped, described and valued. Appropriate technology for mining is discussed and a baseline study of habitats to be developed is done. There is ongoing monitoring to be done for all developments. Management options are clearly articulated.

b) The mining company c) The impact on the physical environment; the impact on biodiversity and the health of Devils; how

the impacts can be reduced; how areas will be rehabilitated; concerns of all stakeholders are considered; consideration of all alternatives to mining here as well as the no mine alternative.


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d) ‘Economic capital’ is the means with which to create wealth. In the case of the Tarkine this is the mineral deposits in the area. ‘Natural capital’ is the intrinsic worth of the environment if it was to remain undisturbed, and the values this gives to humans e.g. clean air and water, recreation and biodiversity.

Comments a) It was surprising that despite guidelines being in the notes, many did not see them and scored

poorly. Those who obviously used the notes scored well. b) There were many wrong responses here, such as the Federal government and conservationists. c) Many chose to include risk assessment and cost/benefit analysis here. Those who responded well

but missed the alternatives to mining consideration missed a mark.

d) The word ‘capital’ was sometimes misunderstood (not a major centre). ‘Economic capital’ was generally well answered; not so ‘natural capital’ (not the value of resources to the economy). The values of biodiversity clean water and air and recreation were generally not specified.

Question 19

Slogan Principle of Sustainability ‘Reduce, reuse, recycle’ Efficient use of resources ‘All there is now is all there ever will be’ Intergenerational Equity or Ecological

Integrity ‘You never know with GMO’ Precautionary Principle ‘Live simply so that others may simply live’ Intragenerational Equity ‘When you come back as a whale you’ll be glad you put Greenpeace in your will”

Intergenerational Equity or Ecological Integrity

Comments There was some confusion here, but many scored full marks. Intragenerational Equity and Intergenerational Equity were sometimes put in the wrong boxes.

Question 20 Putting a price on water and electricity evokes the User Pays Principle which encourages the sustainable use of these commodities. When people have to pay for water and electricity they will look for ways to save money and not waste the resource. (They may buy more efficient dishwashers too). Comments Unfortunately many thought utilities and commodities referred to the dishwasher and were only concerned with saving money and getting “sustainable” appliances. These answers were not penalized if they could relate the dishwashers to sustainable use of water and electricity.


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Question 21 a) Paper is a renewable resource, recyclable and is biodegradable, Polystyrene is cheap, doesn’t

impact on forests and can be recycled to make other products. b) There will be fewer throw-‐aways and therefore less use of resources, recycling energy and tipping

space. c) This is a cost that the manufacturer doesn’t bear. The disposal of the cups is an external cost

borne by the local council. Comments

a) this question wasn’t a problem for most, although to say paper was recyclable and biodegradable

only scored one mark.

b) Many answers just repeated the information about one use without explaining the sustainability of this.

c) Although this was in the notes, many had no idea of this concept. PART 5 -‐ CRITERION 8 (ANALYSIS OF DATA) Question 22 a) 1.25 month or any number up to 1.5 months was one full mark. One month was given half marks. As

the question asked for ‘the first mushroom’ any answer with a range of time was given a half mark.

b) 200 -‐ 205 g was given a full mark. Many candidates struggled to know when the third month should be and gave an answer of 0-‐200g was given a half mark.

c) 200 g x 30 days = 6000g [assuming 30 days]. Some astute candidates knew each month was 30 days because in the graph: 135 days ÷ 4.5 months = 30 days. Answers with 5800 and 6200 g were also given a full mark as these results assumed 28 or 31 days.

d) Ratio of 40/60 (manure/straw) and 3 L water for a full mark (half mark for each).

e) Increasing the amount of water applied to the mushrooms showed a corresponding increase in yield up to 3.0 L. Greater than this was too wet, and the yield significantly decreased between 3 and 4L. Acceptable answers for full marks needed to mention the increasing yield and the decreasing yield between 3 and 4L. If no numbers were included a half mark was deducted.

Comments a) This question was well answered.

b) This question was moderately well answered although determining the third month was the most

challenging aspect for the candidates. Understanding that you are called “one year old” after you


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complete one year of living (your first year) and thus the third month is between 2 and 3 on the time scale was not well understood.

c) Errors in 22b could not be penalised in 22c. Candidates with the correct process (and resulting ‘correct’ answer) were also given a full mark even though they used an incorrect result from part (b). This question should have stated ‘30 days for one month.’

d) Virtually all candidates could read this table and this was very well answered

e) A surprising number of candidates wrote answers that were very general e.g. ‘by designing a range of conditions of manure/straw and water volume the candidate was able to determine the optimal growing conditions’. This was awarded no marks as this did not describing the resulting change in mushroom yield.

Question 23 a) One full mark was given if the line of best fit was a straight line through the middle of each group of

data points. Half marks were awarded if the line was at the bottom or at the top of all the data groups. A curve or a line that connected all the dots was awarded nothing.

b) A line graph should be used as there is continuous data (altitude) available for the independent variable on the x axis.

c) Full marks were given to results around 2 m. For full marks the candidate’s line of best fit had to match their answer for this question.

d) Full marks were given to results around 0.5 or 0.3m. For full marks the candidate’s line of best fit had to match their answer for this question.

e) Acceptable answers were (but not limited to) ! line graph ! averages ! show data points clearly (not on top of each other) ! mean with error bars ! trend line does not extend past data points.

f) i) ! outlier ! anomaly ! rogue point. ii) Answers that mentioned the point should be omitted from data analysis (averages) or ignored but included in the discussion and if possible remeasured were awarded one full mark.

Comments a) Most candidates answered this correctly.

b) This answer was given fully in the information sheet but was used by very few candidates. Answers

that fully discussed the relationship between the two variables and that a line of best fit allows for prediction were awarded one full mark.

d) A surprising number of candidates could correctly predict the heights for 23c and 23d without drawing a line of best fit.


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e) Candidates that suggested more data points or other changes to the experimental design were awarded no mark as the question clearly related to data presentation.

f) Candidates who called it ‘Point A’ were humorous but were awarded no marks. Question 24 a) Rainfall (however if part 24b and 24c correctly described the relationship between temperature

and population then temperature was awarded a full mark) b) The pattern of population mimics the rainfall pattern but has a lag period, i.e. as rainfall increases

population has a corresponding increase. A similar statement of temperature was also accepted. c) Rainfall: The insects rely on plant sap that flows more readily after rain resulting in more growth

and new shoots for food. Many insects also breed in water and have emerged during and after the high rainfall and die out during the dry season. Temperature: During the warmer months more sunlight and photosynthesis would make the environment more productive and the population hatches and grows rapidly. During the cooler months the insects either die or migrate.

d) Acceptable answers were (but not limited to) !predators !daylight hours!food availability

!disease !migration !seasons !insect hatches etc. Comments c) A well described link between rainfall and the link that resulting increase in population was given full

marks. Generally well done.

d) A very easy one mark. Question 25 a) coal b) wind/solar/biofuels. c) A switch away from ‘dirty’ coal to ‘cleaner/greener’ technologies that will reduce CO2 emissions. d) Oil consumption will still increase with increasing (exponential) population growth and demand for

oil in transportation but with decreased availability (peak oil) the price will be forced up and it will only be a moderate increase between 2010 and 2040. If the candidates only mentioned declining petroleum supplies 1 mark was awarded. Mentioning that the increasing oil demand (due to population growth) will be shared by alternative or new green technologies was awarded 1 mark.

Comments a) Only a few candidates noticed the assumption (misprint) that 2010 is the current year.


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b) Very few candidates were able to see the great increase relative to the very small 2010 value. A difficult question.

c) Coal is not expected to ‘run out’ in the next few decades thus any answer that only stated that the

‘predicted decline will be due to no more coal resources was awarded no marks. Surprisingly few candidates gave the correct answer.

d) This question was very poorly answered and only a few candidates achieved full marks. Clearly

candidates are either not aware of peak oil or did not relate it to this question. Unfortunately many candidates did not address the ‘relatively slight predicted increase’ and stated that oil supplies will increase in compensation for coal supplies declining (from the previous question) and missed the point of the question.

Question 26 a) i) 46 seater bus when full

ii) 0.032 kg greenhouse gases per km. b) The car’s emissions are shared between the passengers.

c) 1.6 L: passengers : driver 0.06:0.20 simplifies to 1:3.33

d) 3L: passengers : driver 0.08:0.32 simplifies to 1:4 The ratios are not the same (this

concluding sentence was not required for full marks).

e) Carpooling reduces the amount of greenhouse gasses per person by approximately the number of people in the car i.e. 4 people (3L engine) releases 4 x less per person than the driver alone. A greater reduction is found in the larger car engine (3L vs. 1.6 L).

Comments a) Most candidates failed to read the title ‘per person’ and erroneously divided this answer by 46. b) If candidates mentioned that carpooling means less cars on the road a half a mark was given. c) This question was poorly answered with many candidates not knowing that a ratio involves

multiplication not subtraction. If candidates correctly wrote all four numbers from the graph a half a mark was given.

d) A great many answers were accepted for full marks for this question as long as data was included.

If no data was included one mark only was awarded. If the ratio was not found in c) then full marks could still be obtained by using data directly from the graph.


Page 20 of 20

Question 27 a) Transect

b) Diagram A: 40 – 45m

Diagram B: 25 – 30m Diagram C: 35 – 40m Two answers needed to be incorrect to lose a half a mark.

c) There are no Eucalypt species in the ecosystem that has never been burnt. Eucalypt trees have died as they only live for 350-‐450 years and cannot regenerate beneath a closed canopy in the myrtle rainforest (light levels on the forest floor are too low). Eucalypts regenerate well after a fire. Answers that did not include a reason for the described difference were awarded one mark.

d) 35 – 45 m (from Diagram C -‐ 180 years since the last fire). As the scale should have been easier to read half a mark was given for 50m or 30m but no mark if the height was given as 60 m and greater. A few candidates said the height doubled and this was awarded one mark.

Comments This question was confusing to candidates as the labelling indicated that there were less species in Diagram A compared to Diagram B and C. Candidates erroneously concluded that there is less diversity in the Temperate Rainforest (Myrtle climax community) compared to a Mixed Eucalypt Forest. Marking was generous as the labelling should have included all the species present in each Diagram. Note: There is a general inaccurate understanding of ash beds and nutrients. Much of the soil nutrients are lost in a fire to the atmosphere. The nutrients that remain have been altered so they are more ‘readily available’ for plant uptake and there is an immediate flush of growth. After fire the soil is generally depleted as the organic matter portion of the soil is lost. (This is especially serious as rainfall and winds easily erode the remaining ash with little or no protective vegetation). With little organic matter the nutrient and water holding ability of soil is reduced and takes decades if not hundreds of years to recover.

TASMANIAN QUALIFICATIONS AUTHORITY

ASSESSMENT PANEL REPORT

EVS315109 Environmental Science

8% (14) 23% (39) 38% (64) 31% (53) 170

9% (18) 17% (33) 45% (88) 29% (58) 197

11 % 19 % 39 % 31 %

10 % 22 % 38 % 29 %

11 % 19 % 39 % 30 %

40% (68) 60% (102) 34% (57) 66% (113)

52% (102) 48% (95) 35% (68) 65% (129)

45% 55% 31% 69%

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