Inquiry Question 2: How do genetic techniques affect Earth's biodiversity?
Evaluate the effects of biotechnology on the genetic diversity of agricultural and natural populations, and the impact on biodiversity
A focused answer to the HSC Biology Module 6 dot point on biotechnology and biodiversity. The narrowing effect of monocultures and cloning, gene flow to wild relatives, herbicide and insecticide resistance, conservation applications (gene banks, de-extinction), and an evaluative judgement on net impact.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
NESA wants you to evaluate, not just describe, the effect of biotechnology on biodiversity. Cover both agricultural and natural populations, give specific named examples for each side of the argument, and end with a justified judgement.
The command word "evaluate" is doing the heavy lifting: you must weigh strengths against limitations and reach a supported conclusion. Marks are lost by candidates who list effects without judging them, or who treat biotechnology as uniformly good or uniformly bad.
The answer
Biodiversity has three levels: genetic diversity within species, species diversity within ecosystems, and ecosystem diversity within the biosphere. Biotechnology affects all three.
Negative effects on agricultural biodiversity
Monoculture and varietal narrowing. Industrial agriculture promotes a small number of high-yielding transgenic or hybrid varieties. The result is genetic uniformity across large areas:
- Bt cotton accounts for more than 90 percent of cotton in India and the United States.
- Most commercial Cavendish bananas are genetic clones, leaving the crop highly vulnerable to Tropical Race 4 of Panama disease.
- Holstein dairy cattle worldwide trace much of their genetics to fewer than 100 elite sires.
Loss of landraces. Patented seed and standardised varieties displace farmer-saved seed and traditional landraces, eroding the genetic base from which future crops will be bred. The Mexican maize landrace decline is a documented case.
Cloning narrows livestock pools. Reproductive cloning of high-value bulls and racehorses concentrates allele frequencies still further.
The diagram below contrasts a monoculture of one GM cultivar with a genetically diverse population, and shows how a transgene can flow from a crop to a wild relative.
Negative effects on natural biodiversity
- Gene flow to wild relatives
- Transgenes can introgress from crops into wild populations via cross-pollination, especially in canola, sunflower and rice. The escaped genes can either swamp local adaptation or, if they confer fitness, create "superweeds."
- Non-target organisms
- Bt toxin is generally specific to Lepidoptera, but some studies show effects on non-target butterflies (Monarch caterpillars on milkweed exposed to Bt corn pollen). Recent meta-analyses suggest the net effect on non-target arthropods is small or positive due to reduced spraying.
- Resistance evolution
- Glyphosate-tolerant crops have selected for glyphosate-resistant weeds (Palmer amaranth, horseweed). Bollworm resistance to Bt has emerged in India and the United States. Resistance management requires refuges, crop rotation and rotation of modes of action.
Positive effects: conservation biotechnology
- Whole genome sequencing
- Sequences of endangered species identify the level of inbreeding, regions of low diversity and disease alleles. Used in the Tasmanian devil insurance population to manage devil facial tumour disease and in the kakapo recovery programme.
- Assisted reproduction
- Artificial insemination, in vitro fertilisation, embryo transfer and somatic cell nuclear transfer maintain populations of critically endangered species. The northern white rhino is being preserved through oocyte collection and IVF.
- Gene and seed banks
- The Svalbard Global Seed Vault stores more than one million plant accessions. The Frozen Zoo at San Diego cryopreserves cell lines from over 10,000 animals. The Australian PlantBank holds seeds and tissue cultures of native flora.
- De-extinction and genetic rescue
- CRISPR allows the introduction of lost alleles into living relatives. The Colossal Mammoth Project aims to edit Asian elephant cells with mammoth alleles. The thylacine project in Australia (Colossal and University of Melbourne) aims to use dunnart cells. Genetic rescue has been used in Florida panthers and black-footed ferrets.
- Reduced land conversion (land sparing)
- Higher per-hectare yields from biotechnology can reduce pressure to clear new habitat, indirectly protecting biodiversity. The strength of this effect is debated.
Summary table
| Effect | Direction | Mechanism | Example |
|---|---|---|---|
| Monoculture | Negative (agricultural) | Variety standardisation | Cavendish banana |
| Gene flow | Negative (natural) | Cross-pollination | Canola to wild Brassica |
| Resistance evolution | Negative (natural) | Selection pressure | Glyphosate-resistant weeds |
| Cloning | Negative (agricultural) | Narrow effective population | Holstein cattle |
| Sequencing | Positive (conservation) | Inbreeding management | Tasmanian devils |
| Cryopreservation | Positive (conservation) | Preservation of allele diversity | Svalbard Seed Vault |
| De-extinction | Positive (speculative) | Restoration of lost alleles | Mammoth project |
Examples in context
Tasmanian devil insurance population and DFTD. Devil Facial Tumour Disease has reduced wild Tasmanian devil (Sarcophilus harrisii) populations by more than 80 percent since 1996. Save the Tasmanian Devil Program uses biotechnology to maintain a genetically diverse insurance population at zoos including Sydney's Taronga. Researchers sequence individual devils' MHC genes (responsible for immune recognition) and selectively breed pairs to maximise allelic diversity, since DFTD spreads partly because wild devils have very low MHC variation. By preserving over 250 captive animals with curated genetics, the program preserves variation that may otherwise vanish from the wild, ready to be reintroduced as immune-competent founder populations.
Wollemi pine clonality and disease risk. The Wollemi pine (Wollemia nobilis), rediscovered in 1994 in Wollemi National Park west of Sydney, exists as fewer than 100 mature wild trees and shows extremely low genetic diversity (almost identical at all sequenced loci, suggesting recent clonal reproduction). Botanic gardens around the world propagate the species by cuttings, which produces genetically identical plants. While this safeguards the species against extinction by fire (catastrophic in 2019-2020), it offers no resistance variation against the introduced soil pathogen Phytophthora cinnamomi, which has already killed wild Wollemi pines. Biotechnology has paradoxically both saved and entrenched the genetic uniformity of this living fossil.
Evaluation
Biotechnology's effect on biodiversity is split:
- Agricultural genetic diversity is on a clear downward trend driven by varietal consolidation and patented seed. This is the dominant negative impact.
- Natural genetic diversity receives mixed effects. Gene flow and resistance evolution are real concerns; conservation applications partially offset these.
The most defensible judgement is that biotechnology accelerates the loss of agricultural genetic diversity while providing important conservation tools that did not previously exist. The net outcome depends heavily on policy choices: seed-saving rights, refuge requirements, biobank funding and gene-flow regulation.
Exam-style practice questions
Practice questions written in the style of NESA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
2021 HSC9 marksReproduction of transgenic salmon for aquaculture is strictly controlled. Techniques include: (1) homozygous (TT) female (XX) breeding stock kept in quarantine; (2) hormone treatment causing sex reversal so females develop male organs and sperm; (3) that sperm used to fertilise eggs from wild-type non-transgenic salmon; (4) eggs treated with pressure shock to prevent meiosis II so offspring are triploid (XXX, unable to develop sex organs); (5) offspring grown in inland tanks. Analyse how these techniques protect and preserve biodiversity.Show worked answer →
Analyse each technique's effect on biodiversity (within the species and the ecosystem). Sample answer (key points): Biodiversity is the variety of gene pools within species and the variety of species in ecosystems; escaped transgenic salmon could reduce it. Physical isolation (techniques 1 and 5 - quarantine and inland tanks) prevents transgenic salmon escaping; if they escaped they might have a survival advantage, pass on the transgene, outcompete wild fish and reduce both genetic and species biodiversity. Hormone-induced sex reversal (technique 2) produces sperm carrying only X chromosomes (parents are genetically female), so all offspring are female. Using wild-type eggs (technique 3) prevents inbreeding of transgenic stock and introduces hybrid vigour, preventing accumulation of mutations. Pressure shock (technique 4) blocks meiosis II to produce infertile, triploid offspring, so the transgene cannot be passed on. Together, physical isolation, reproductive control and hybrid vigour protect biodiversity within the salmon population and in ecosystems. Marks: 9 = extensive knowledge of biotechnology, reproduction and biodiversity with scientific analyses of the techniques tied to protecting biodiversity; 7-8 = thorough; 5-6 = sound; 3-4 = some; 1-2 = basic/relevant information. Reference multiple levels of biodiversity and how each technique affects it.
Source: NESA 2021 HSC Biology examination and marking guidelines.
2023 HSC5 marksA table lists biotechnologies used in cattle farming with examples: selective breeding (dairy breeds from highest-milk cows), artificial insemination (one bull siring cattle in 50 countries), whole-organism cloning (30-40 cloned cattle, not commercial), hybridisation (Bos taurus x Bos indicus), and transgenic organisms (human serum albumin in milk, not widespread). With reference to the table, evaluate the effect of biotechnologies on the biodiversity of cattle.Show worked answer →
Judge each biotechnology's effect on biodiversity using the table, then give an overall judgement. Sample answer: Biotechnologies can increase, maintain or decrease biodiversity. Artificial insemination generally reduces biodiversity because one male can sire many offspring, lowering the number of bulls passing on genes. Selective breeding reduces biodiversity because only individuals with desired traits breed. Whole-organism cloning reduces biodiversity (clones are genetically identical), but as it is not used commercially in cattle its current impact is small. Transgenic organisms could increase genetic diversity by introducing new genes, but again are not widely used. Hybridisation can increase biodiversity through new gene combinations (or reduce it if hybrids are bred in preference to original breeds). Overall judgement: these biotechnologies have the overall effect of decreasing biodiversity in cattle. Marks: 5 = extensive understanding with relevant references to the table AND an informed judgement; 4 = sound with some references and a suitable judgement; 3 = understanding of the effect on biodiversity; 2 = identifies an effect; 1 = relevant information. Common error: using own examples instead of the table, and linking biotech to the organism rather than to biodiversity.
Source: NESA 2023 HSC Biology examination and marking guidelines.
2022 HSC2 marksExplain a possible outcome of the use of artificial pollination on subsequent populations.Show worked answer →
Link repeated use of one pollen source to reduced genetic diversity over generations. Sample answer: If pollen from one plant is used to artificially pollinate a large number of plants, this leads to many offspring that are genetically similar. Over time, if this is repeated in subsequent generations, it will reduce the genetic diversity of the population. Marks: 2 = explains an outcome of artificial pollination on populations; 1 = some relevant information. The key is showing cause (one pollen source -> similar offspring) and effect (reduced genetic diversity/biodiversity in later generations).
Source: NESA 2022 HSC Biology examination and marking guidelines.
Practice questions
Original practice questions graded from foundation to exam level, each with a full worked solution. Try them before revealing the solution.
foundation2 marksIdentify two ways biotechnology can reduce the genetic diversity of an agricultural crop.Show worked solution →
Award 1 mark for each correct, distinct way (any two of the following).
1 mark - monoculture / varietal narrowing. Planting a single high-yielding transgenic or hybrid genotype over a large area means most plants are genetically near-identical, so allelic variation across the crop falls.
1 mark - cloning of elite cultivars. Propagating one cultivar by cuttings or tissue culture (for example Cavendish bananas) produces genetically identical plants, concentrating allele frequencies.
Accept also: replacement of traditional landraces and farmer-saved seed with a few patented varieties. Naming a method without linking it to reduced genetic variation does not earn the mark.
foundation2 marksDefine biodiversity and name its three levels.Show worked solution →
1 mark - definition. Biodiversity is the variety of living things, measured as variation at several levels.
1 mark - the three levels. Genetic diversity (allele variation within a species), species diversity (the number and variety of species in an ecosystem) and ecosystem diversity (the variety of ecosystems in the biosphere).
A response that gives only one level, or confuses genetic with species diversity, caps at 1 mark.
foundation3 marksExplain how gene flow of a transgene from a GM crop to a wild relative can affect biodiversity.Show worked solution →
- 1 mark - the mechanism
- Pollen from the GM crop can cross-pollinate a closely related wild plant, so the transgene introgresses (crosses) into the wild population's gene pool.
- 1 mark - the fitness effect
- If the transgene confers an advantage (for example herbicide tolerance), wild plants carrying it may gain a survival/reproductive advantage and increase, potentially creating a hard-to-control "superweed".
- 1 mark - the biodiversity link
- The spreading transgene can swamp locally adapted alleles and reduce the genetic diversity of the wild population, and the advantaged weed may outcompete other species, lowering species diversity.
Full marks need the route (cross-pollination), the selective effect, and an explicit link to a level of biodiversity.
core4 marksCompare the effect of monoculture of a single GM cultivar with maintaining a genetically diverse crop population, in terms of genetic diversity and resilience to disease.Show worked solution →
Award up to 4 marks for a genuine comparison (both situations addressed for both features).
Genetic diversity (2 marks). A monoculture of one GM cultivar is genetically uniform - nearly every plant carries the same alleles, so the gene pool is narrow. A diverse population contains many genotypes, so allelic variation across the crop is high.
Resilience to disease (2 marks). Because the monoculture shares the same alleles, a pathogen that overcomes that genotype can destroy the entire crop (for example Cavendish banana and Tropical Race 4). In a diverse population, some genotypes are likely to carry resistance alleles, so the disease spreads more slowly and the population is buffered.
The discriminator is "uniform gene pool, all-or-nothing vulnerability" (monoculture) versus "varied gene pool, resistance present in some plants" (diverse). Describing only one side does not reach full marks.
core4 marksIn a fictional rice crop, a Bt-resistance allele is present in 2 percent of a pest insect population after 5 years of Bt rice cultivation with no refuge crop planted. Predict how this frequency will change over the next 10 years and explain the mechanism.Show worked solution →
- 1 mark - prediction
- The frequency of the resistance allele will rise sharply (it could exceed 50 percent), so Bt rice becomes progressively less effective.
- 1 mark - the selection pressure
- The Bt toxin is a strong selective agent: susceptible insects are killed before reproducing, while resistant insects survive.
- 1 mark - differential reproduction
- Surviving resistant insects pass the resistance allele to their offspring, so its frequency increases each generation (directional selection).
- 1 mark - role of the refuge
- With no refuge of non-Bt rice, there are few susceptible insects left to dilute the resistance allele by mating with resistant survivors, so resistance spreads even faster.
A response that predicts the rise but does not name selection / differential survival and reproduction caps at 2 marks.
core5 marksDescribe two ways biotechnology is used to conserve biodiversity, and explain how each preserves genetic diversity.Show worked solution →
Award up to 2-3 marks per application (description plus the genetic-diversity link), to a maximum of 5.
Whole genome sequencing for managed breeding (2-3 marks). Sequencing endangered individuals reveals inbreeding, regions of low diversity and disease alleles; breeders then pair animals to maximise allelic (for example MHC) diversity in the offspring. Used in the Tasmanian devil insurance population, this preserves variation that might otherwise be lost from the wild.
Gene / seed banks (cryopreservation) (2-3 marks). Facilities such as the Svalbard Global Seed Vault and San Diego's Frozen Zoo store seeds, tissue or cell lines at very low temperatures. This banks alleles (including from landraces and rare individuals) so the diversity can be restored if a population crashes or a variety is lost.
Accept also assisted reproduction (AI, IVF, embryo transfer, SCNT) maintaining founder diversity in small populations. Each application must be tied explicitly to preserving allele variation, not just "saving the species".
exam7 marksEvaluate the impact of biotechnology on biodiversity. In your answer, describe one application that reduces biodiversity and one that increases or preserves it, and justify whether the net global effect is positive or negative.Show worked solution →
"Evaluate" requires a justified judgement weighing both sides, not two separate descriptions. A Band 6 answer references specific named examples and reaches a defensible conclusion.
- Application that reduces biodiversity (2 marks)
- Monoculture / varietal consolidation: a few high-yielding transgenic or hybrid cultivars displace landraces and farmer-saved seed, so the agricultural gene pool narrows (for example Bt cotton dominating cotton in India and the United States; clonal Cavendish bananas). Add gene flow of transgenes to wild relatives as a natural-population example.
- Application that increases or preserves biodiversity (2 marks)
- Conservation biotechnology: whole genome sequencing and managed breeding preserve allelic diversity (Tasmanian devil MHC genes), while cryopreservation banks alleles (Svalbard Seed Vault, Frozen Zoo). These tools retain or restore variation that did not previously have a safeguard.
- Justified judgement (2-3 marks)
- A supported conclusion: biotechnology accelerates the loss of agricultural genetic diversity (the dominant negative trend) while providing powerful conservation tools for natural populations; the net outcome depends on policy - seed-saving rights, refuge requirements, gene-flow regulation and biobank funding. State the judgement explicitly (for example "net effect is negative for agricultural diversity but the conservation gains are real and growing, so the overall sign is policy-dependent"). Listing features without an explicit judgement caps below full marks.
exam6 marksA botanic garden safeguards a critically endangered native conifer that survives as fewer than 100 wild trees with very low genetic diversity by propagating it from cuttings. Evaluate this conservation strategy with respect to its impact on the species' biodiversity.Show worked solution →
Target a sequenced response: the benefit, the genetic limitation, then a justified judgement.
- Benefit (2 marks)
- Propagation by cuttings rapidly produces many individuals from limited stock, creating an ex-situ insurance population safe from catastrophic events such as bushfire (relevant to the Wollemi pine after the 2019-2020 fires). The species is protected from immediate extinction.
- Genetic limitation (2 marks)
- Cuttings are clones: every propagated plant is genetically identical, so the strategy adds no new genetic diversity. With a uniform gene pool the population has no resistance variation against a novel threat - for example the soil pathogen Phytophthora cinnamomi, which has killed wild Wollemi pines.
- Judgement (1-2 marks)
- A supported conclusion: cloning is justified as an emergency safeguard against extinction, but because it entrenches genetic uniformity it is not sufficient on its own; it should be paired with banking of any remaining genetic variation and, where possible, sourcing distinct genotypes. A response without an explicit, balanced judgement caps below full marks.