Active learning ideas
The carbon and nitrogen cycles are the chemical foundations of life, moving essential elements through the Earth's spheres. This topic examines the reservoirs (where elements are stored) and the fluxes (how they move) for both carbon and nitrogen (ACSES042, ACSES043). Students investigate how biological processes like photosynthesis and nitrogen fixation are balanced by geological processes like volcanic outgassing and rock weathering.
Activity 01
Students act as carbon or nitrogen atoms, moving between 'stations' (atmosphere, ocean, soil, plants) based on the roll of a die. They keep a travel log to see where they spend the most time and what processes moved them.
What are the major reservoirs of carbon and nitrogen?
Activity 02
Groups are given a scenario of a local Australian farm using high levels of fertiliser. They must map the nitrogen's path from the bag to the local river and eventually to the Great Barrier Reef, identifying the 'leaks' in the cycle.
How do biological processes drive these cycles?
Activity 03
Should we focus on 'nature-based' sequestration (planting trees) or 'technological' sequestration (carbon capture and storage)? Students research and debate the efficiency, cost, and permanence of different ways to 'sink' carbon.
How do human activities alter the carbon and nitrogen cycles?
A few notes on teaching this unit
Watch Out for These Misconceptions
Plants get their 'food' (carbon) from the soil.
Plants get their carbon from CO2 in the atmosphere through photosynthesis. The soil provides minerals and water, but the 'bulk' of a tree's mass is literally made of air. A 'mass balance' activity comparing a seed to a tree can help prove this.
The nitrogen in the air (78%) is directly usable by animals and plants.
Atmospheric nitrogen (N2) is triple-bonded and very stable. It must be 'fixed' into ammonia or nitrates by bacteria or lightning before life can use it. A 'lock and key' analogy helps students understand the necessity of nitrogen-fixing bacteria.
Methods used in this brief
Photosynthesis, Respiration, and Energy Flow
Investigate the processes of photosynthesis and cellular respiration. Students will model energy flow and matter transfer through food webs.
8 methodologies
Environmental Change and Human Impacts
Evaluate the impact of human activities on ecosystems and biogeochemical cycles. Students will discuss mitigation and adaptation strategies for environmental changes.
8 methodologies