HSC Exam Practice

Sample response. Biodiversity is the variety of life. It is measured at three levels: genetic diversity (allele variation within a population or species), species diversity (variety of species in a habitat) and ecosystem diversity (variety of ecosystems, communities and ecological interactions).

Marking notes. 1 mark for a correct definition of biodiversity; 1 mark for naming all three levels (genetic, species, ecosystem). All three required for full marks.

Sample response. Genetic diversity is the variation in alleles within a single species or population, while species diversity is the variety of different species in a habitat. A monoculture of a single GM crop cultivar reduces genetic diversity within the crop because almost all plants share the same alleles. A herbicide-tolerant GM crop sprayed on a wide area may also reduce species diversity in surrounding vegetation by removing non-target plants and the invertebrates that depend on them.

Marking notes. 1 mark for correctly distinguishing genetic from species diversity; 1 mark for a valid example of a biotechnology affecting genetic diversity; 1 mark for a valid example affecting species diversity. Examples need not be the ones modelled.

Sample response. Widespread use of one elite genotype means that most plants in the region carry essentially the same alleles, so the within-species allele variation falls. Older, less productive cultivars are abandoned and their alleles are lost from the gene pool. The resulting genetic uniformity reduces resilience, because if a new pathogen or environmental stress targets that genotype, the entire crop is similarly susceptible.

Marking notes. 1 mark for identifying that one genotype dominates → alleles drop. 1 mark for explaining that older cultivars / alleles are lost from the gene pool. 1 mark for explicitly linking reduced genetic diversity to reduced resilience (vulnerability to pathogens / environmental change).

Sample response. Conservation genetics uses DNA data to identify low-diversity or inbred populations, then guides breeding management (e.g. pairing unrelated individuals, prioritising rare alleles) to maintain genetic variation. For a threatened species this reduces inbreeding depression and increases the long-term chance of survival.

Marking notes. 1 mark for stating that conservation genetics uses DNA information to inform management; 1 mark for naming a concrete benefit (e.g. reduces inbreeding, preserves rare alleles, supports continuity of a threatened population). Accept named examples (Tasmanian devil MHC management, mountain pygmy possum) as evidence of the benefit.

Sample response. Biodiversity operates at three levels, so a single biotechnology can act differently at each. A GM crop may improve species-level food security by raising yield while simultaneously reducing genetic diversity within the crop because only a few cultivars are sown. A pest-resistant GM trait may also support some non-target species in surrounding habitats while changing ecological interactions in unpredictable ways. The mismatch between positive and negative effects at different levels is exactly what the lesson treats as a mixed outcome.

Marking notes. 1 mark for stating that biodiversity has multiple levels (or that effects can be evaluated at multiple levels). 1 mark for a specific example of a positive effect at one level. 1 mark for a specific example of a negative or uncertain effect at another level. Full marks require the student to clearly tie the positive and negative effects to different levels.

Sample response. Productivity measures the output of a single crop or species per unit area or time (e.g. tonnes per hectare). Biodiversity measures the variety of life at the genetic, species and ecosystem levels. The two are confused because higher productivity is often visible and economically valuable, while biodiversity loss (especially genetic-level loss) is harder to see — so a "yield up" outcome can be reported as "biodiversity up" even when allele variation has fallen.

Marking notes. 1 mark for correctly distinguishing productivity (output) from biodiversity (variety, three levels). 1 mark for explaining the source of the confusion (visibility / measurement asymmetry, or simply that productivity and biodiversity measure different things).

Sample response (a). Yield rises steadily from 100% of baseline at Year 0 to about 156% at Year 15. The number of cultivars planted falls from 100% to about 17% over the same period. Native pollinator species richness falls from 100% to about 78%. So one indicator rises, two fall.

Sample response (b). The headline equates yield with the environment, but yield is a measure of productivity, not biodiversity. The same dataset shows that genetic-level biodiversity has fallen sharply (the number of cultivars dropped from 100% to ~17%) and species-level biodiversity in pollinators has also fallen (~22% drop). At the ecosystem level, fewer native pollinator species suggests altered pollination interactions. Across the three biodiversity levels, two have fallen and one indicator (yield) has risen, so the honest verdict is a mixed outcome — not unambiguously good for the environment.

Marking notes. Part (a) — 1 mark for describing the yield rise with figures; 1 mark for describing both biodiversity indicators falling with figures (cultivars + pollinators). Part (b) — 1 mark for distinguishing productivity (yield) from biodiversity; 1 mark for citing the genetic-level fall (cultivars) from the data; 1 mark for citing the species- or ecosystem-level fall (pollinators) from the data and concluding "mixed" rather than "good".

Sample response. The claim that biotechnology is always beneficial for biodiversity is too absolute. Biodiversity is measured at three levels — genetic, species and ecosystem — and a single biotechnology can have different effects at each, so the honest verdict is that biotechnology effects are positive, negative or mixed depending on context and the level being assessed. Some biotechnologies clearly reduce biodiversity at certain levels. Widespread adoption of one elite GM cultivar (for example a herbicide-tolerant canola or a GM Bt cotton) is a monoculture: it raises productivity but collapses genetic diversity within the crop because alleles from older cultivars are lost from the gene pool. As the lesson's Cavendish-style risk case warns, this uniformity reduces resilience — a single new pathogen or environmental stress can damage the whole crop because every plant has the same susceptibility. Other biotechnologies can support biodiversity. Conservation genetics, for instance, has been used to manage MHC variation in the Tasmanian devil population threatened by Devil Facial Tumour Disease: DNA fingerprinting and SCNT-based genetic rescue can restore lost alleles and reduce inbreeding, supporting both the genetic-level biodiversity of the population and species-level continuity. Even here the outcome is not unambiguously positive — it depends on ongoing management, founder genetics and ecosystem support — but the contrast with the monoculture case is clear. Across the three levels, the GM monoculture is positive for productivity but negative for within-crop genetic diversity and potentially for surrounding species and ecosystem diversity, while conservation genetics is positive for within-population genetic and species-level diversity but limited in ecosystem-level reach. The claim is therefore rejected: biotechnology is not always beneficial for biodiversity. The defensible statement is that biotechnology effects on biodiversity are conditional — positive at one level, negative or uncertain at another — and the strongest HSC judgement explicitly evaluates effects at all three biodiversity levels rather than treating biotechnology as automatically good or automatically bad.

Marking notes. 1 mark — defines biodiversity and names the three levels (genetic, species, ecosystem). 1 mark — names a valid biotechnology that may reduce biodiversity (e.g. GM monoculture / Bt cotton / single-cultivar canola) and identifies the level affected. 1 mark — names a valid biotechnology that may support biodiversity (e.g. conservation genetics / SCNT genetic rescue / Tasmanian devil MHC management) and identifies the level affected. 1 mark — explicitly links one biotechnology's effect to more than one biodiversity level. 1 mark — distinguishes productivity from biodiversity, or rejects equating one with the other. 1 mark — uses the lesson's balanced "may help / may reduce / depending on" language and rejects both "always good" and "always bad" claims. 1 mark — reaches an explicit evaluative judgement that the claim is rejected and that biodiversity effects are mixed/conditional, framed in precise lesson terminology.