Investigate the ecological systems, biodiversity and abiotic factors of a chosen Australian natural environment and explain how its components interact.

What this dot point is asking

You must investigate a real Australian natural environment and explain how its ecological components interact. Examiners want evidence that you can describe both the parts of the system and the processes that connect them, using your own observation and collected data.

Abiotic and biotic factors

An ecosystem has two broad sets of components. Abiotic (non-living) factors include sunlight, temperature, rainfall, wind, soil type, salinity, slope and the availability of water. Biotic (living) factors include producers (plants), consumers (herbivores, carnivores, omnivores), decomposers (fungi and bacteria) and the relationships between them.

In the Coorong, for example, the abiotic factors of salinity and water depth strongly control which species survive. High salinity favours salt-tolerant samphire and brine shrimp, while the freshwater inflow from the Murray mouth supports very different life. Change one abiotic factor and the whole biotic community shifts.

Biodiversity

Biodiversity describes the variety of life at three levels: genetic diversity within a species, species diversity within a community, and ecosystem diversity across a landscape. High biodiversity generally makes an environment more resilient, because more species means more pathways for energy and nutrients and more capacity to recover from disturbance such as fire, drought or flood.

Australian environments are often biodiverse but fragile. Many species are endemic (found nowhere else) and adapted to specific conditions, so even small disturbances from trampling, weeds or feral animals can have large effects.

Energy flow and food webs

Energy enters almost every ecosystem through photosynthesis. Producers capture solar energy and convert it to chemical energy. This energy then flows through trophic levels: producers to primary consumers to secondary and tertiary consumers, with decomposers recycling material at every stage.

Energy is lost as heat at each transfer, so only a fraction (commonly cited as around ten percent) passes to the next level. This is why there are many plants, fewer herbivores and only a small number of top predators. A food web shows the many feeding relationships in a community and is more realistic than a single food chain because most organisms eat, and are eaten by, several others.

Nutrient cycling

Unlike energy, nutrients are recycled. The water cycle, carbon cycle and nitrogen cycle move matter between the atmosphere, soil, water and living organisms. Decomposers are central: when an animal dies or a leaf falls in a stringybark forest, fungi and bacteria break it down and release nutrients back into the soil for plants to reuse. Australian soils are frequently old and nutrient-poor, which is why many native plants have specialised strategies such as nitrogen-fixing root nodules or fire-triggered seed release.

Reading a real environment

For your investigation you choose at least one environmental area and gather your own evidence. Useful methods include quadrat sampling of vegetation, transect walks, water testing for salinity and pH, recording weather data, and observing animal signs and tracks. You then interpret what these observations reveal about the health and functioning of the system, and you consider historical, cultural (including First Nations) and personal perspectives on the area.

Strong responses connect the observed parts to the processes: you do not just list species, you explain how the abiotic conditions shape which species are present and how energy and nutrients move between them.