Biology: Units 1 to 4 explained
From ecosystems and cells to heredity and homeostasis
The study of living systems at every scale, from molecules and cells to organisms and ecosystems. Senior Biology is the most popular senior science nationally and feeds courses such as HSC Biology, VCE Biology and QCE Biology; it suits students interested in health, medicine, environmental and life sciences.
Honest note on coverage: ChalkBee has no Year 11-12 worksheets for this subject yet. This page is curriculum reference, how the national subject is organised, plus links to the ChalkBee Foundation to Year 10 content that genuinely leads into it.
The four units
Like every ACARA senior secondary subject, Biology runs across four units: Units 1 and 2 are usually taken in Year 11, Units 3 and 4 in Year 12, with achievement standards described for each pair.
Students examine ecosystems and the relationships between their biotic and abiotic components. They use classification systems to collect, compare and evaluate data about organisms, and analyse how energy and matter move through ecosystems and how populations change.
The scale shifts inward: cell structure and function, and how the interdependent parts of the cell system work together. Students then investigate how multiple interacting systems (exchange of gases, nutrients and wastes) sustain multicellular organisms.
The mechanisms of heredity: DNA, genes and the ways inheritance patterns can be explained, modelled and predicted. Students connect genetics to the theory of evolution by natural selection and the evidence that supports it.
How organisms hold their internal environment steady as external conditions change: homeostasis at cellular and whole-organism levels. The unit also covers infectious disease, its transmission and impact, and the factors that affect its spread.
How it is assessed
Set by each state authority, typically school-based assessment including at least one substantial practical or field investigation, plus an external written exam. Working scientifically (designing investigations, evaluating claims and data) is assessed alongside content knowledge.
Remember: ACARA publishes the national subject, but your state authority runs the actual course, assessment and certificate. See how each state and territory differs.
Where ChalkBee fits today
ChalkBee has no Year 11-12 Biology worksheets yet. The Year 9-10 science codes below are the direct feeders: genetics and evolution lead into Unit 3, body systems into Unit 4.
Related Foundation to Year 10 content
- AC9S10U01: Meiosis, mitosis and heredity
Year 10 genetics is the direct base for Unit 3's heredity content.
- AC9S10U02: Evolution by natural selection
Year 10 evolution leads straight into Unit 3's continuity of life.
- AC9S9U01: Body systems and feedback
Feedback and body systems at Year 9 are the entry point for Unit 4's homeostasis.
Other Science senior subjects
Unit structure verified against the official ACARA senior secondary Biology pages (Australian Curriculum v8.4). Descriptions are paraphrased in our own words; the authoritative wording is ACARA's, and your state or territory authority's syllabus governs what is actually taught and assessed. Senior secondary is a live area of change, so confirm current details with your state authority before relying on them.