Ausgeology. Senior secondary lessons

SACE Stage 1 Earth and Environmental Science · Topic 6: Biosphere

Ecosystems and cycles.

The dunes and seagrass on Adelaide’s coast are an ecosystem run on sunlight and recycled matter. Survey the dunes, follow the energy and the carbon, nitrogen and phosphorus, and build a report that answers one question.

How the lesson works

1 · Survey the site

Screens 2 to 4. Get to know the site, plan and carry out a transect survey across the dunes, and explain the patterns in your data.

2 · Energy and matter

Screens 5 and 6. Measure photosynthesis in a pondweed lab, compare the productivity of ecosystems, and model carrying capacity.

3 · Cycles of matter

Screens 7 and 8. Follow carbon, nitrogen and phosphorus through the spheres, and find out why Adelaide lost its seagrass.

4 · Report

Screens 9 and 10. Weigh the ecosystem services, give your advice, put the report together, then show what you know.

Your project

Driving question: What keeps the dunes and seagrass on Adelaide’s coast alive, and what should be done to protect them?

By screen 9 you will have a field study report: introduction, method, results, discussion, energy, populations, the cycles, limitations, and your advice to the council. Each screen adds a section.

What we are learning

How biotic and abiotic factors shape where organisms live, how energy from the sun enters an ecosystem and limits its populations, how carbon, nitrogen and phosphorus cycle between the spheres, and what ecosystems do for people.

I can

  • 1describe the biotic and abiotic features of an ecosystem and explain how a change in them creates a different environment.
  • 2plan a transect survey and record biotic and abiotic data in the field.
  • 3explain the distribution and abundance of organisms from the factors measured.
  • 4explain how photosynthesis stores energy and what net primary production is.
  • 5explain how biotic and abiotic factors set carrying capacity.
  • 6describe the carbon cycle’s processes, its main sinks, and the fast and slow cycles.
  • 7describe the processes of the nitrogen cycle, including eutrophication.
  • 8explain the phosphorus cycle and why the atmosphere plays little part in it.
  • 9discuss the benefits of ecosystem services.

SACE Stage 1 Earth and Environmental Science, Topic 6: Biosphere. This lesson covers the topic’s statements on ecosystems, energy, carrying capacity, ecosystem services and the carbon, nitrogen and phosphorus cycles. The teacher notes at the end quote them in full.

My notebook

Printable activity

Field study sheet

Three pages for a real transect or the one on screen 3: a planning checklist, a quadrat table for percentage cover and abiotic readings, graph grids for a kite diagram and a factor, and a planner for the report. Print one per student, or one per pair in the field.

Field study sheet (PDF) Editable (Word)

1Survey the site

The site.

What makes up the ecosystem from the beach, over the dunes, and out to the seagrass?

Your study site is modelled on Wara Wayingga - Tennyson Dunes on Adelaide’s coast. Start by sorting what is living and what is not, and by finding out how the dunes change from the sea inland.

This screen · about 25 minutes

  1. Read about the reserve and its zones.
  2. Sort the parts of the ecosystem into biotic and abiotic.
  3. Read how a change in these features can create a different environment, then answer the check.
  4. Write the introduction to your report.

Wara Wayingga - Tennyson Dunes

The 17 ha Wara Wayingga - Tennyson Dunes Conservation Reserve, with 1.4 ha of crown land next to it, lies on the Adelaide metropolitan coast between West Lakes and the sea. It is “one of the last remnant coastal dune systems along the Adelaide metropolitan coast” (Tennyson Dunes Working Group, 2019). Of the 52 original plant species found there, 16 are of conservation significance (National Parks and Wildlife Service SA). The Department for Environment and Water has managed the reserve since 2015 (Succession Ecology, 2023), guided by a working group that includes representatives of Kaurna, the department, the City of Charles Sturt and the Tennyson Dunes Group (Tennyson Dunes Working Group, 2019).

Offshore, the Adelaide coast has seagrass meadows. More than 5,000 ha of seagrass has been lost along the metropolitan coastline (EPA SA, 2008). Screen 8 looks at why.

From the beach inland, as the management plan and 2023 survey describe it

Foredune

Open grassland of hairy spinifex (Spinifex hirsutus), with coast daisy-bush and grey saltbush standing out above it.

Swale

Open shrubland of coast daisy-bush (Olearia axillaris) and seaberry saltbush (Rhagodia candolleana).

Hind dune

Shrubland of coast daisy-bush and sea box (Alyxia buxifolia); the ridge is dominated by coast beard-heath (Leucopogon parviflorus).

Rear of the reserve

Very low woodland of drooping sheoak (Allocasuarina verticillata) and native pine (Callitris gracilis), in an area being rehabilitated.

Sources: Tennyson Dunes Working Group (2019); Succession Ecology (2023). The survey calls the zones by number; the names here are the usual ones for a dune profile.

Biotic and abiotic

“An abiotic factor is a non-living part of an ecosystem that shapes its environment” (National Geographic): on land, examples include temperature, light and water, and in the sea, salinity and currents. Biotic factors are the effects of living things on the environment and on each other (European Environment Agency). “Abiotic and biotic factors work together to create a unique ecosystem” (National Geographic).

Biotic or abiotic?

When the features change, the environment changes

On a dune, plants change the conditions for the plants that come after them. “At each stage of succession, the plant community alters the physical environment”: it adds organic matter to the soil, shades the ground and gives shelter, and “the initial colonisers facilitate recovery of other species that might require more shelter, soil and organic matter” (Dahm, 2014).

Changes can also run the other way. Weeds such as bridal creeper and gazania “can out-compete native plants and degrade habitat”, and the 2023 survey found “Extensive foot traffic” in the hind dunes (Succession Ecology, 2023). Coastal dunes are eroded by trampling, off-road vehicles and grazing (Government of South Australia, 2016). Offshore, the loss of seagrass “contributed to considerable and ongoing erosion of the Adelaide foreshore” (Society for Ecological Restoration).

Which is an example of a biotic feature changing the abiotic environment of the dunes?

For your report

1Survey the site

Survey.

How do you measure the plants and the conditions along a line from the beach inland, so that the data can answer your question?

Plan the survey, then run it. Two transects across the dunes give you two sets of readings to compare.

This screen · about 35 minutes

  1. Read how a transect survey is done.
  2. Sort the planning decisions into good and poor practice.
  3. Record every quadrat on transect A, then on transect B.
  4. Write the method for your report.

Transects and quadrats

“The most effective way to investigate an environmental gradient is by sampling along a line (or transect)” (WJEC). On a dune, students “start from the water’s edge and move inland on a transect line perpendicular to the shoreline” (Bournda Environmental Education Centre). At stations along the line you place a quadrat, often 1 m square, and “estimate what percentage of the area enclosed by the quadrat is occupied by each species” (Field Studies Council). Percentage cover is a judgement rather than an exact measurement (Royal Geographical Society), which is one reason to repeat it.

At each station you also measure the abiotic factors. An anemometer measures wind speed; a pH test can be done in the field or on soil samples in the lab; soil water is found by weighing a fresh sample, drying it and weighing it again; and organic matter by weighing a dry sample, burning off the organic matter and weighing what is left. “Ideally all measurements should be made at the same time of day, with the same technique at each site” (Field Studies Council).

Good or poor practice?

Why run a second transect a short way along the beach from the first?

For your report

1Survey the site

Patterns.

Why does each plant grow where it does, and how sure can you be?

Turn your readings into a kite diagram and a graph of each abiotic factor. Then explain the distribution and abundance of the plants.

This screen · about 35 minutes

  1. Read the kite diagram for each transect.
  2. Graph each abiotic factor and compare the two transects.
  3. Read what the sources say drives the zones, then answer the check.
  4. Write your results, discussion and limitations.

Record quadrats on screen 3 first: these charts use your readings. The kite diagram shows the transect chosen on screen 3.

Show the numbers as a table

What drives the zones

Dune zonation “tends to reflect variations in key stressors in the physical environment”: “sand deposition and burial, salt spray episodes, sand movement, wind velocity and sand blasting” (Dahm, 2014). As a foredune builds up and out, “sand inundation and salt spray levels decrease, while nutrient levels and vegetation cover increase”, and its landward slope is colonised by woody shrubs that “prefer more stable conditions” (Sloss and others, 2012). Rolling spinifex (Spinifex sericeus), a close relative of the Tennyson species and a sand-binding grass, tolerates drought, soil salinity and salt spray (Botanic Gardens and State Herbarium SA). Further back, “strong salt laden winds” prevent trees from establishing near the coast (Limestone Coast and Coorong Coastal Action Plan).

The soil changes too. On a beach-ridge plain in Tasmania, where the dunes get older inland, pH tended to fall with age as shell carbonate was leached out and organic matter, with its acids, built up (Bowman, 1987). Some South Australian coastal soils “can be quite alkaline” because they come from limestone (State Flora SA).

The readings on screen 3 are modelled to follow these patterns; they are not measurements from Tennyson. In a real survey, the pattern on one transect may not be repeated on the next, so compare them before you explain anything.

Why is spinifex the main plant on the foredune, but not further inland?

For your report

2Energy and matter

Energy.

Where does the energy in the dunes and the seagrass come from, and how much of it is there?

Every plant you recorded is turning light into chemical energy. Test what limits the rate in a pondweed lab, then compare how productive different ecosystems are.

This screen · about 35 minutes

  1. Read how photosynthesis stores energy.
  2. Use the virtual lab to find what limits the rate. Record at least six readings.
  3. Read about net primary production and compare ecosystems.
  4. Answer the check and add energy to your report.

Photosynthesis

In photosynthesis, carbon dioxide and water make sugar and oxygen using energy from sunlight (OpenStax Concepts of Biology):

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

Light “energy is converted into stored chemical energy” in the glucose (OpenStax Biology 2e). In plants, photosynthesis generally happens in the leaves, inside chloroplasts. That stored energy feeds almost everything else in the ecosystem.

“The main factors affecting rate of photosynthesis are light intensity, carbon dioxide concentration and temperature” (Royal Society of Chemistry). The rate is limited by whichever factor is in shortest supply, the limiting factor. As light increases, the rate rises until another factor limits it. As temperature rises, the rate increases towards the enzymes’ optimum, then falls “as enzymes are denatured, until it stops” (Royal Society of Chemistry).

Net primary production

“The rate at which photosynthetic primary producers incorporate energy from the sun is called gross primary productivity.” Net primary productivity is the energy that remains in the producers “after accounting for the organisms’ respiration and heat loss” (OpenStax Biology 2e): the energy available to everything that eats them. At Silver Springs in Florida, producers took in 20,810 kcal per square metre each year, used 13,187 of it for respiration or lost it as heat, and left 7,633 kcal for the primary consumers (OpenStax Biology 2e; the source’s own figures do not quite add up, as the difference is 7,623).

Of all the solar energy reaching Earth, “only 1 to 2 percent is available to be captured by plants” (Britannica). At each step up a food chain only a small share of the energy, about 10 percent on average, passes on (Britannica); at Silver Springs it was about 14.5 percent between the first two levels (OpenStax Biology 2e).

Show the numbers as a table

Another widely used table, credited to Whittaker and Likens (1973), gives some different values, such as 2,000 for tropical rainforest and 70 for desert shrub. Neither table has a row for seagrass on its own.

In the lab, the bubble rate rises steeply as light goes from 0 to 40%, then hardly rises from 80 to 100%. What is limiting the rate at 100% light?

For your report

2Energy and matter

Carrying capacity.

How many animals can an ecosystem feed, and what happens when there are more?

The energy and matter available set a limit to how big a population can grow. On Kangaroo Island, koalas went past that limit.

This screen · about 30 minutes

  1. Read what sets carrying capacity.
  2. Run the population model with and without overbrowsing.
  3. Follow the Kangaroo Island koalas and the Top End buffalo, then answer the check.
  4. Add what limits populations to your report.

What sets the limit

Carrying capacity is “the maximum population size that a particular environment can support” (OpenStax Biology 2e). For plants, “the amount of water, sunlight, nutrients, and the space to grow are the important resources”; for animals, they include “food, water, shelter, nesting space, and mates” (OpenStax Biology 2e). Biotic factors such as disease, competition and predation, and abiotic factors such as climate extremes and fire, also limit populations (Edwards and Edwards, 2011).

A population with plenty of resources grows quickly at first; then “growth levels off at the carrying capacity of the environment”, giving an S-shaped curve (OpenStax Biology 2e). If numbers rise so fast that the population overshoots, “carrying capacity can be degraded to a lower level” (University of Portland, 2021).

Koalas on Kangaroo Island

1923–25

18 koalas were released on Kangaroo Island (Masters and others, 2004), brought from French Island in Victoria (Molsher, 2017).

By 1994

The population “was significantly impacting the health of manna gums at the landscape scale” (Molsher, 2017). Large stands of manna gum have been lost through overbrowsing, and the loss of trees causes erosion along river banks (Department for Environment and Water, 2017).

1996–97

A population control program began, based on an estimate of 5,000 koalas (Masters and others, 2004). By 2017 more than 12,700 koalas had been sterilised and 3,800 moved to the South East of the state (Department for Environment and Water, 2017).

2015

A survey estimated about 25,000 koalas in native vegetation and 23,000 in commercial blue gum plantations: about 48,500 in all (Molsher, 2017). The plantations had added food.

2019–20

Bushfires burnt about half the island, and an estimated 80% of the koalas were lost (Dunstan and others, 2021).

2025

The island’s mayor put the population at about 20,000, a figure read into the South Australian Parliament; it is not a published survey (SA Hansard, 2025).

Sources give different figures for several of these: the program’s start (1996 or 1997), and the 2010 estimate (13,000 or 14,270). The teacher notes list them.

Buffalo in the Top End

Asian water buffalo were brought to northern Australia from South-east Asia between 1826 and 1866. After the buffalo hide industry collapsed in 1956, their numbers “grew exponentially until they were declared an environmental nuisance in 1978”, and by 1985 there were about 340,000 (Gorman and others, 2007). On the floodplains, buffalo pathways called swim channels have let salt water into freshwater plains, particularly in the Mary River area, which “has led to the loss of large areas of paperbark forest” (NT Government). In Kakadu National Park numbers were reduced “from 20 000 to under 250 in 1996” (Australian Government, 2011), but in 2019 there were estimated to be at least 161,250 across the Top End (Territory NRM).

By 2015 almost half of Kangaroo Island’s koalas lived in blue gum plantations. What did the plantations do?

For your report

3Cycles of matter

The carbon cycle.

Where does the carbon in a spinifex leaf come from, and where does it go next?

Energy flows through an ecosystem and is lost as heat, but matter is recycled. Carbon carries the stored energy of photosynthesis, and it moves between the air, living things, the ocean and rocks.

This screen · about 35 minutes

  1. Step through the carbon cycle.
  2. Compare the sizes of Earth’s carbon stores, and the fast and slow cycles.
  3. Read about blue carbon on the Adelaide coast, the Amazon and fire in Arnhem Land, then sort the processes.
  4. Answer the checks and add the carbon cycle to your report.

Carbon carries the energy

Photosynthesis builds carbon from the air into sugar and stores the Sun’s energy in it. When plants, animals and decomposers break the sugar down in respiration, “oxygen combines with sugar to release water, carbon dioxide, and energy” (NASA Earth Observatory). So as carbon moves through the cycle, energy is stored, passed on and transformed: from light, to chemical energy in biomass, to the energy that living things use and lose as heat. Burning fossil fuels, a form of combustion, releases energy that plants stored millions of years ago.

Show the numbers as a table

The figures for the ocean, soils, vegetation and the atmosphere are the stores before industry, from the IPCC’s 2021 assessment as set out by Stocker (2024). Different sources define the rock store differently, so its size varies a great deal between them. NOAA says the ocean “holds about 50 times more carbon than the atmosphere”.

Two speeds

The fast carbon cycle

“The time it takes carbon to move through the fast carbon cycle is measured in a lifespan.” It is “largely the movement of carbon through life forms on Earth”, and it moves 1,000 to 100,000 million tonnes of carbon each year (NASA Earth Observatory).

The slow carbon cycle

Carbon takes 100 to 200 million years to move between rocks, soil, ocean and atmosphere, and only 10 to 100 million tonnes move through this cycle each year. Volcanoes return carbon to the air (NASA Earth Observatory).

Of the carbon dioxide people have added to the air, about 30% has gone into the ocean, about 25% has been taken up by plants on land, and about 45% has stayed in the atmosphere (NASA Earth Observatory). The ocean and land plants are acting as carbon sinks.

Two carbon sinks

Seagrass on the Adelaide coast

Blue carbon “is the carbon captured and stored in coastal ecosystems including seagrass meadows, saltmarshes and mangroves” (Department for Environment and Water). Seagrasses “can store up to twice as much carbon per hectare than terrestrial forests” (Department for Environment and Water, 2021), and “Much of this organic carbon is stored in the sediments that the plants grow in” (CSIRO). Seagrass, mangroves and saltmarsh cover only 2% of the world’s seabed but are responsible for 50% of the carbon transfer to ocean sediments (CSIRO). Damaging them “causes much of this stored carbon to be released” (CSIRO).

The Amazon rainforest

Amazonia “has been shown to be an important carbon sink over recent decades”, but that sink “seems to be in decline” because of deforestation and climate change (Gatti and others, 2021). Aircraft measurements from 2010 to 2018 showed that southeastern Amazonia “acts as a net carbon source” (Gatti and others, 2021), while western Amazonia “is still a relatively weak carbon sink” (Denning, 2021).

Fire and carbon in Arnhem Land

Fire returns carbon to the air quickly. In west Arnhem Land, Traditional Owners and Aboriginal ranger groups manage fire across the West Arnhem Land Fire Abatement project, “the first savanna fire abatement project anywhere in the world”, which covers 28,000 square kilometres (Clean Energy Regulator). Customary practice is to “Burn early in the dry season at times of heavy dew and little wind, so that fires burn slow and cool, and go out overnight” (ALFA, 2023). The early burns leave “a patchwork of firebreaks” that can limit late-season wildfires (Clean Energy Regulator), and in its first 7 years the project cut its emissions of methane and nitrous oxide “by 37.7%, relative to the pre-project 10-year emissions baseline” (Russell-Smith and others, 2013). The carbon dioxide from the fires is not counted, on the assumption that “CO2 emissions in one burning season are negated by growth of vegetation in subsequent growing seasons” (Russell-Smith and others, 2014).

Where does the carbon go?

Why does burning fossil fuels raise the carbon dioxide in the air, when respiration by every living thing on Earth does not keep raising it?

The West Arnhem project counts the methane and nitrous oxide from its fires, but not the carbon dioxide. Why?

For your report

3Cycles of matter

Nitrogen and phosphorus.

Why did the Adelaide coast lose its seagrass, and what do the nitrogen and phosphorus cycles have to do with it?

Plants need nitrogen and phosphorus to build proteins and DNA. Both cycle through soil, water and living things, but only one of them passes through the air.

This screen · about 40 minutes

  1. Step through the nitrogen cycle.
  2. Put the steps of eutrophication in order, and read what happened to Adelaide’s seagrass.
  3. Step through the phosphorus cycle and sort the processes.
  4. Answer the check and add nitrogen and phosphorus to your report.

Wattles on the dunes

Wattles evolved in response to “low nutrient soils and poor water availability across much of Australia” (Royal Botanic Gardens Sydney). They cope because “Acacias, like most legumes, are well known as nitrogen fixing plants”: with the help of bacteria that form nodules on their roots, they “are able to extract atmospheric nitrogen from otherwise low nitrogen soils” (Royal Botanic Gardens Sydney). The CSIRO describes the nodules taking “nitrogen from the air, which plants cannot use” and fixing it “in a form they can use” (CSIRO, 2002). When the plants drop leaves and die, decomposers return that nitrogen to the soil for other plants.

Eutrophication: put the steps in order

What happened to Adelaide’s seagrass

More than 5,000 ha of seagrass has been lost along the Adelaide metropolitan coastline; another report gives more than 6,000 ha between 1949 and 2007 (EPA SA, 2008; Government of South Australia, 2016). The Adelaide Coastal Waters Study found that “nutrient rich inputs from stormwater, sewage treatment plants and industrial discharges are the main causes for loss of seagrasses” (EPA SA, 2008). Excess nutrients promote the growth of epiphytes, algae that grow on the seagrass leaves (EPA SA, 2008). Mapping of nitrogen in seagrass found that “Dense seagrass meadows only occurred in areas unimpacted by plumes throughout the year” (Fernandes and others, 2015).

The study recommended cutting the nitrogen entering the coast from 2,400 tonnes a year in 2003 to around 600 tonnes a year (EPA SA, 2008). Since then, “seagrass cover within sampling sites has been improving after historical losses”, most likely because of “reduced nutrient loads” (Willoughby and Meakin, 2023). Seagrass is also being restored by placing hessian sacks on the sea floor near the meadows, for young seagrass to attach to and grow (Department for Environment and Water, 2021).

Why the atmosphere hardly matters for phosphorus

Nitrogen gas makes up 78% of the air, an abundant store of nitrogen (Britannica). Phosphorus is different: there are “No stable gaseous P compounds”, and it moves through the air mainly as dust (University of Hawaiʻi). For land soils, “atmospheric deposition is relatively unimportant” (Ruttenberg, 2004). So nitrogen lost from an ecosystem can be fixed again from the air within a season, but phosphorus washed into the sea returns to land only when sea-floor sediment is lifted up and weathered, over geological time. Much of Australia has “Ancient and highly weathered soils with very low levels of natural phosphorus” (Soil Quality).

Nitrogen, phosphorus or both?

Why did the plan to bring back Adelaide’s seagrass set a target for cutting nitrogen in discharges to the sea?

For your report

4Report

Your report.

What does this coast do for people, and what would you advise to protect it?

The dunes and the seagrass do work that people would otherwise have to pay for. Weigh those benefits, finish your advice, and put your report together.

This screen · about 40 minutes

  1. Sort the ecosystem services the dunes and seagrass provide.
  2. Answer the check.
  3. Write your conclusion and advice.
  4. Gather your report, read it through, and copy it into a document.

Ecosystem services

Ecosystem services are the benefits people get from processes in ecosystems. Dune plants trap and bind the sand, and the dunes act as “a buffer between the land and the sea, protecting landward vegetation from high energy storms” (Department for Environment and Water). Seagrass meadows “provide important nursery ground for snapper, calamari, whiting and blue swimmer crab” (EPA SA, 2023). The EPA estimates that one hectare of seagrass is worth more than $26,000 a year (EPA SA, 2024); a study of fisheries alone gave a much lower value for South Australia (Jänes and others, 2020).

Dunes, seagrass or both?

Which is the best evidence that losing seagrass also costs people?

For your report

Put your report together

Your notes save in this browser as you type. The report gathers them in order. Copy it into a document to add your kite diagram, chart and photos.

5Show what you know

Show what you know.

Nine questions, one for each of the I can statements on screen 1. You get one try at each, so think before you tap.

Trampling kills the spinifex along part of the foredune. What is most likely to happen next?

A student records one quadrat every 20 m along a single transect. What would most improve the reliability of the results?

On a transect, beard-heath cover is highest where wind is low and organic matter is high. What is the best conclusion?

Producers capture energy from sunlight, then use some of it in their own respiration and lose some as heat. What is the energy left over, available to the consumers, called?

Koalas on Kangaroo Island overbrowsed manna gums until many trees died. What happened to the carrying capacity?

Which process moves carbon from the atmosphere into the biosphere?

In a waterlogged swale, bacteria turn nitrate in the soil into nitrogen gas. Which process is this?

Why does phosphorus lost to the sea take so long to return to the land?

A developer wants to flatten a vegetated foredune for a car park. Which ecosystem service would be lost?

Printable activity

Field study sheet

Three pages for a real transect or the one on screen 3: a planning checklist, a quadrat table for percentage cover and abiotic readings, graph grids for a kite diagram and a factor, and a planner for the report. Print one per student, or one per pair in the field.

Field study sheet (PDF) Editable (Word)
For teachers

Curriculum

SACE Board of South Australia, Stage 1 Earth and Environmental Science Subject Outline (reissued for 2025), Topic 6: Biosphere. NT students take the subject as part of the NTCET. The topic outline begins:

The fossil record provides evidence of the diverse life forms that have existed over time. Students interpret and evaluate different types of fossil evidence and explore the connections of fossils to past environments.

Students explore how interactions among the spheres affect the communities of organisms in different ecosystems. They investigate the importance of processes such as photosynthesis and the cycling of nutrients and energy for sustaining life on Earth.

The topic’s Science Understanding statements and dot points that this lesson covers:

In any one location, the characteristics and interactions of the geosphere, atmosphere, hydrosphere, and biosphere give rise to unique and dynamic communities.

  • Describe the difference between biotic and abiotic features of an ecosystem.
  • Explain how a change in these features can create different environments.
  • Identify, measure, and record the appropriate characteristics in a field location.
  • Describe how these factors may affect the distribution and abundance of organisms found in a particular location.

Energy from the sun is converted into chemical energy in the form of biomass.

  • Explain the importance of photosynthesis in converting light energy into chemical energy that is stored in glucose.
  • Explain that net primary production (NPP) is the rate at which plants in an ecosystem produce net useful chemical energy.

The availability of energy and matter are one of the main determinants of ecosystem carrying capacity.

  • Explain how biotic and abiotic factors affect carrying capacity.

Processes occurring in ecosystems that achieve major transformations of resources that benefit humans are known as ecosystem services.

  • Discuss the benefits of ecosystem services.

Energy is stored, transferred, and transformed in the carbon cycle.

  • Describe the key processes and the role they play in the carbon cycle, including photosynthesis, respiration, decomposition, and combustion.
  • Identify the main carbon sinks.
  • Describe the differences between the fast and slow carbon cycle.
  • Identify where these processes occur in the carbon cycle.
  • Explain the interactions between the forms of carbon and each of the spheres.

Biogeochemical cycling of nitrogen and phosphorus in matter occurs between the geosphere, atmosphere, hydrosphere, and biosphere.

  • Describe the key processes in the nitrogen cycle, including nitrification, denitrification, nitrogen fixation, ammonification, eutrophication.
  • Identify where these processes occur in the nitrogen cycle.
  • Explain the interactions between the forms of nitrogen and each of the spheres.
  • Discuss the key processes in the phosphorus cycle including the conversion of inorganic phosphate to organic phosphate and the role of earth and environmental science processes.
  • Explain why the atmosphere does not play a significant role in the phosphorus cycle but does in the nitrogen cycle.

The topic’s statements on early life, fossils and extinction are covered in the first Topic 6 lesson, Life through deep time. In the outline’s table, the statement on ecosystem services is in the same row as the one on carrying capacity; the lesson treats them as two statements.

Where the lesson covers them:

  • Biotic and abiotic features, and how a change in them creates different environments: screen 2 (the reserve and its zones, the sort, q-site), x1.
  • Identify, measure and record characteristics in a field location: screen 3 (planning, the transect, q-survey) and the field sheet, x2.
  • Distribution and abundance: screen 4 (the kite diagram, the abiotic graphs, what drives the zones, q-patterns), x3.
  • Photosynthesis and net primary production: screen 5 (the pondweed lab, the NPP chart, q-energy), x4.
  • Carrying capacity and the biotic and abiotic factors that set it: screen 6 (the population model, the Kangaroo Island koalas, buffalo in the Top End, q-capacity), x5.
  • The carbon cycle, its processes, sinks, fast and slow cycles and the spheres: screen 7 (the cycle, the stores chart, blue carbon, the Amazon, savanna burning in Arnhem Land, the sort, q-carbon, q-fire), x6.
  • The nitrogen cycle, including eutrophication: screen 8 (the cycle, wattles, the eutrophication chain, Adelaide’s seagrass, q-nutrients), x7.
  • The phosphorus cycle and the part the atmosphere plays: screen 8 (the cycle, the explanation, the sort), x8.
  • Ecosystem services: screen 9 (the sort, q-report, the advice), x9.

The lesson uses these of the outline’s possible contexts:

Conduct a field investigation focused on an environmental monitoring and ecosystem study.

Obtain, tabulate, and graph data on photosynthesis.

Discuss how the Amazon basin acts as a carbon sink.

Explore fast and slow carbon cycles.

Choose one example to describe the interaction between humans and natural ecosystems services.

The transect on screen 3 is a model. It is meant to prepare students for real fieldwork, not to replace it: the field sheet is laid out for a real dune or a schoolyard transect, and the same report works for either.

Key concepts of science as a human endeavour from the outline, and where they are used:

Science informs public debate and is in turn influenced by public debate; at times, there may be complex, unanticipated variables or insufficient data that may limit possible conclusions.

Screen 8: the Adelaide seagrass, where the evidence on causes and recovery has built up over 30 years; screen 9: the advice to council.

New technologies improve the efficiency of scientific procedures and data collection and analysis. This can reveal new evidence that may modify or replace models, theories, and processes.

Screen 7: aircraft measurements showing part of the Amazon is now a carbon source; screen 8: mapping of nitrogen plumes along the coast, which showed dense seagrass only outside them (Fernandes and others, 2015).

Stage 1 is assessed through an investigations folio and skills and applications tasks. The field study report the lesson builds suits the investigations folio; adapt the sections to your school’s task sheet.

How the lesson is taught

The lesson is a project. Krajcik and Shin set out six features of project-based learning: a driving question, learning goals, scientific practices, collaboration, using technological tools, and creating an artefact (as reported by Markula and Aksela, 2022). Here the driving question is on screen 1, the learning goals are the I can statements, the practices are planning a survey, recording data and graphing it, and the artefact is the field study report, which grows one section per screen. Students who work in pairs on the survey and the sorts cover the collaboration.

The evidence is encouraging but not settled. Thomas (2000) found project-based learning “seems to be equivalent or slightly better than other models of instruction” for general achievement, and warned that it “is relatively challenging to plan and enact”. A meta-analysis of 30 studies found a mean effect size of 0.71 on achievement (Chen and Yang, 2019), and a randomised trial of high school chemistry and physics units found students “performed 0.20 standard deviations higher than control students” (Schneider and others, 2022). A review for MDRC called the evidence “promising but not proven” (Condliffe and others, 2017). One caution matters for this lesson: in a study of how teachers run projects, none of the twelve schools studied showed evidence of using a driving question (Markula and Aksela, 2022). So return to the driving question at the start of each lesson, and have students answer it in their conclusion.

  • Timing. About five and a half hours: seven 50-minute lessons. Lesson 1: screens 1 and 2. Lesson 2: screen 3. Lesson 3: screen 4. Lesson 4: screens 5 and 6. Lesson 5: screen 7. Lesson 6: screen 8. Lesson 7: screens 9 and 10. Add time for real fieldwork if you do it.
  • Pairs. Pairs can share the survey: one records Transect A and the other Transect B, then they compare. Each student keeps their own report.
  • The report. Notes save in the browser on the device being used. If students change devices, they should copy the report out on screen 9 at the end of each lesson, or keep their notes on the field sheet.
  • Discussion points. After screen 4, ask what the transect can and cannot show about cause. After screen 6, ask whether fertility control or moving koalas is the better answer, and what evidence would decide it. After screen 8, ask who should pay to cut nitrogen in wastewater.
  • The field sheet has a quadrat table for a real transect, a page for the abiotic readings and graphs, and planning prompts for the report. Collect it with the report.

Handle with care

  • The reserve is on Kaurna Country, and the working group that guides its management includes Kaurna representatives (Tennyson Dunes Working Group, 2019). The lesson tells no Kaurna stories. If your class visits, follow your school’s protocols and the reserve’s guidance.
  • Dunes are fragile. On a visit, keep to the trails and boardwalks, as the reserve asks, and sample only where you have permission; screen 3 makes this one of the planning points.
  • The koala case involves sterilising and moving native animals. Some students feel strongly about it. Keep the discussion on the evidence: the condition of the trees, the numbers, and what each option would do.

Misconceptions the screens target

  • Plants get their food from the soil (screen 5). They make sugar from carbon dioxide and water; the carbon comes from the air.
  • Energy is recycled in an ecosystem like matter (screen 7). Matter cycles; energy flows through and is lost as heat at each step.
  • A correlation along a transect proves cause (screen 4, x3). Several factors change together inland.
  • Carrying capacity is fixed (screen 6, x5). Food added by plantations raised it on Kangaroo Island; overbrowsing lowers it.
  • Nutrients are always good for plants (screen 8, q-nutrients). Too much nitrogen in the sea fed the algae that harmed the seagrass.
  • Phosphorus cycles through the air like nitrogen (screen 8, x8). There is no stable phosphorus gas.
  • Early burning stops savanna fires emitting (screen 7, q-fire). Early fires still emit; the project is credited for emitting less methane and nitrous oxide than its baseline, and the carbon dioxide is left out on the assumption that regrowth takes it back up.
  • Burning fuels and respiration are the same for the carbon budget (screen 7, q-carbon). Respiration is balanced by photosynthesis in the fast cycle; fossil fuels add carbon from the slow cycle.

About the data and the models

  • The transect (screens 3 and 4) is modelled on Wara Wayingga - Tennyson Dunes. The species and their zones follow the management plan and the 2023 vegetation survey (Tennyson Dunes Working Group, 2019; Succession Ecology, 2023). The cover values are made up to follow that zonation. The abiotic readings follow directions the sources give (wind, salt spray and sand movement falling inland, organic matter rising, pH falling as dunes age: Sloss and others, 2012; Dahm, 2014; Bowman, 1987), but the numbers are invented, with seeded random variation. No source we found gives measured values for this reserve, so none are claimed. There is no soil moisture reading because we found no source for its pattern across these dunes.
  • The pondweed lab (screen 5) and the population model (screen 6) are simple models; their notes on screen say how they work. The population model is not fitted to Kangaroo Island.
  • The NPP chart (screen 5) uses the table on a Portland State University course page, credited to McKinney and Schoch (1998). The carbon stores chart (screen 7) uses NASA Earth Observatory for rocks and IPCC AR6 Figure 5.12, as set out by Stocker (2024), for the rest; it is on a logarithmic scale.
  • The three cycle diagrams (screens 7 and 8) are schematic and not to scale; they share one landscape so students can compare them.
  • Quotations in the screens are short excerpts checked against the source pages; where a sentence continues, the lesson quotes only the part shown.

Where sources disagree

  • Plant species at the reserve: 52 original species, 16 of conservation significance (National Parks and Wildlife Service SA), or 57 and 18 (Tennyson Dunes Working Group, 2019). The 2023 survey also records an introduced grass, Thinopyrum junceiforme, alongside the spinifex on the foredune (Succession Ecology, 2023).
  • Seagrass lost off Adelaide: more than 5,000 ha (EPA SA, 2008), more than 6,000 ha between 1949 and 2007 (Government of South Australia, 2016; EPA SA, 2024), or more than 5,200 ha (Society for Ecological Restoration). The surveys cover different years and areas.
  • The main source of nitrogen: the EPA’s Adelaide coastal waters page says industrial sources contribute the most nutrient; the EPA’s 2023 submission calls three wastewater treatment plants major contributors of nitrogen. Screen 8 names stormwater, wastewater and industry together, as the Adelaide Coastal Waters Study does.
  • Recovery: extent “may have stabilised since 2007” (Government of South Australia, 2016); cover “has been improving” (Willoughby and Meakin, 2023); recolonisation in places but continued loss in others (Fernandes and others, 2015).
  • Blue carbon: seagrass stores “up to twice” as much carbon as land forests (Department for Environment and Water, 2021; EPA SA, 2024); blue carbon ecosystems in general “up to four times as much carbon per area” (Department for Environment and Water). Screen 7 uses the seagrass figure.
  • The value of seagrass: more than $26,000 per hectare a year for all services (EPA SA, 2024, which does not give its source), against a fisheries-only value of about $21,200 a year across Australia but $150 for South Australia (Jänes and others, 2020).
  • The rock carbon store: 65,500 billion tonnes (NASA Earth Observatory) or about 75,000,000 Pg in Stocker’s table, which counts all carbonate rock and kerogen. Permafrost: 1,200 Pg (Stocker) or 1,672 Pg for the Northern Hemisphere (NASA).
  • Buffalo numbers: about 340,000 in 1985 (Gorman and others, 2007) or “as many as 350 000” (Australian Government, 2011). The fall in Kakadu came from a control program, not from the buffalo reaching carrying capacity.
  • Ocean and atmosphere: NOAA says the ocean holds about 50 times the atmosphere’s carbon; the pre-industrial stocks in the chart give a higher ratio.
  • Nitrogen fixation: Britannica says about 90 percent of fixation is by bacteria and blue-green algae; Fowler and others (2013) say humans are responsible for about half of all fixation today. They count different things: Fowler counts fixation caused by people, including fertiliser production, as human.
  • Wattle root bacteria: Rhizobium (Royal Botanic Gardens Sydney) or Bradyrhizobium (CSIRO, 2002). Both are rhizobia; the lesson says root-nodule bacteria.
  • Kangaroo Island koalas: the control program began in 1996 or 1997; 2010 estimates of 13,000 or 14,270. NPP: Whittaker and Likens (1973) give some different values from the Portland State table, such as 2,000 for tropical rainforest. The Portland State page gives the units only; its values match standard net primary productivity tables.

Answers at a glance

  • Screen checks: q-site, spinifex traps sand and adds organic matter; q-survey, to see how much readings vary; q-patterns, spinifex tolerates salt spray and moving sand; q-energy, another factor such as carbon dioxide or temperature; q-capacity, added food raised the carrying capacity; q-carbon, burning releases carbon from rock stores; q-fire, regrowth takes back the carbon dioxide but not methane or nitrous oxide; q-nutrients, extra nitrogen fed algae; q-report, seagrass loss has added to erosion of the foreshore.
  • Biotic or abiotic (screen 2): spinifex, bridal creeper and microbes biotic; wind and salt spray, sand, soil pH, light under the shrubs and salinity abiotic.
  • Planning (screen 3): at right angles to the shore, the same quadrat at every station, and repeats are good practice; choosing quadrats by eye, measuring at different times and walking across the dunes are poor.
  • Carbon sort (screen 7): photosynthesis, atmosphere to biosphere; decomposition, biosphere to atmosphere; burning petrol and volcanoes, geosphere to atmosphere; dissolving, atmosphere to hydrosphere; shells settling, hydrosphere to geosphere.
  • Eutrophication (screen 8): nutrients wash in, algae grow too much, they die, bacteria use up the oxygen, fish and seagrass die. Nitrogen or phosphorus: nodules and denitrification, nitrogen; apatite and uplift, phosphorus; uptake, decay and algal blooms, both.
  • Services (screen 9): storm buffer and sand store, dunes; nursery, holding the sea floor and carbon in sediment, seagrass; trapping sand, both.
  • Exit check: x1 sand moves and the shrubs are exposed; x2 more quadrats or a second transect; x3 a link with shelter and organic matter, not proof of cause; x4 net primary productivity; x5 it fell; x6 photosynthesis; x7 denitrification; x8 no gas form, so only by uplift; x9 storm protection and a sand store.

Saved progress

Answers, choices, readings and notes are saved only in this browser on this device. Nothing is sent anywhere.

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Sources by screen

Word list