Unit 4: How does life change and respond to challenges over time?

Evidence for evolution. Covers the fossil record and transitional fossils, biogeography and continental drift, comparative anatomy (homologous, analogous, vestigial structures), and molecular evidence including DNA and protein sequence comparisons and molecular clocks.

Speciation. Covers the biological species concept, allopatric and sympatric speciation, the role of geographical and reproductive isolation, and prezygotic and postzygotic reproductive isolating mechanisms with examples.

Sources of genetic diversity in sexually reproducing populations. Covers independent assortment in metaphase I, crossing over in prophase I, random fertilisation, and the contribution of mutation as the ultimate source of new alleles.

Human evolution. Covers the major trends in hominin evolution (bipedalism, brain size, tool use, dentition), key species from Australopithecus afarensis to Homo sapiens, and the out-of-Africa hypothesis for the global spread of modern humans.

Mutation types. Covers point mutations (silent, missense, nonsense), frameshift mutations (insertions and deletions), block mutations and chromosomal aberrations (inversion, translocation, duplication, non-disjunction), the causes of mutation, and how each type affects the protein product.

Natural selection. Covers the contributions of Darwin and Wallace, the four conditions for natural selection (variation, heritability, selection pressure, differential reproductive success), fitness and adaptation, and how allele frequency changes over time in a population.

Immune system. Covers the innate immune response (physical, chemical and microbiological barriers, inflammation, phagocytosis) and the adaptive response (antigen presentation, helper and cytotoxic T cells, B cells, antibodies, memory cells), with the distinction between humoral and cell-mediated immunity.

Pathogens and disease management. Covers the structure and reproduction of bacteria, viruses, protozoa, fungi and prions; how vaccines produce active immunity and herd immunity; the role and limits of antibiotics and antivirals; and the emergence of antibiotic resistance.

Scientific logbook. Covers what VCAA expects in a logbook, what schools use for authentication, sample logbook entries, and the typical authentication issues that flag a poster for follow-up.

Student-designed practical investigation. Covers the Key Science Skills, scientific poster format, logbook expectations, and how to choose a research question grounded in Unit 3/4 biology.

Evaluating the investigation. Defines validity, reliability, precision and accuracy in VCAA's sense; categorises sources of error (random, systematic, gross); walks through worked examples of error analysis on enzyme and ecology investigations.