§-Unit

Unit 3: Biodiversity and the interconnectedness of life

8 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

Topic 1: Describing biodiversity and ecosystem dynamics

Identify and describe abiotic and biotic factors that influence the distribution and abundance of organisms in an ecosystem, including tolerance ranges and ecological niche

Abiotic and biotic factors. Defines the key physical and biological factors that shape distribution and abundance, explains tolerance ranges with the optimum and limits of tolerance, and contrasts fundamental and realised niches with Australian examples.

9 min read →

Identify and classify organisms using the Linnaean hierarchical system (domain, kingdom, phylum, class, order, family, genus, species) and construct and use dichotomous keys to identify organisms

Classifying organisms. Covers the Linnaean hierarchy from domain to species with named examples, binomial nomenclature rules, and how to construct and use a dichotomous key to identify organisms in a survey.

8 min read →

Describe biodiversity as the variety of all life forms on Earth, including the different plants, animals, micro-organisms, the genes they contain and the ecosystems they form, recognising biodiversity at the genetic, species and ecosystem levels

Three levels of biodiversity. Defines genetic, species and ecosystem biodiversity with named Australian examples, and explains why each level matters for ecosystem resilience and conservation.

7 min read →

Describe ecosystem dynamics, including the role of keystone species and the processes of primary and secondary succession, and explain how species composition changes over time

Ecosystem dynamics. Compares primary and secondary succession with named Australian examples, explains the role of pioneer and climax communities, and defines keystone species with case studies relevant to QCAA stimulus questions.

8 min read →

Describe energy flow through ecosystems including food chains, food webs and trophic levels, and explain biomass, productivity (GPP and NPP) and the 10 per cent rule of trophic efficiency

Energy flow through ecosystems. Defines producers and consumers at each trophic level, distinguishes food chains from food webs, works through biomass, gross and net primary productivity, and explains the 10 per cent rule with worked numbers.

9 min read →

Describe and explain population growth patterns including exponential and logistic models, carrying capacity, density-dependent and density-independent limiting factors, survivorship curves and r and k selection

Population ecology. Contrasts exponential and logistic growth, defines carrying capacity (K) and the difference between density-dependent and density-independent limiting factors, and explains survivorship curves alongside r-selected and k-selected life history strategies.

10 min read →

Describe the cycling of matter through biogeochemical cycles, including the carbon, nitrogen and water cycles, and evaluate the impact of human activities on these cycles

Biogeochemical cycles. Walks through the carbon, nitrogen and water cycles with the named processes QCAA expects (photosynthesis, respiration, nitrogen fixation, nitrification, denitrification, evapotranspiration), and evaluates how fossil fuel use, fertiliser application and land clearing have changed each cycle.

10 min read →

Determine the biodiversity of an ecosystem using measures of species richness, species evenness and Simpson's diversity index, and explain the limitations of these measures

Measuring biodiversity. Defines species richness and evenness, works through Simpson's diversity index step by step with sample data, and outlines the limitations students should mention in exam responses.

9 min read →