VCAA 2022

Why does increasing chloroplast number increase photosynthesis rate?

More chloroplasts = more light-dependent reactions → higher production of ATP and NADPH → faster carbon fixation.

Why is RNA converted to DNA in RT-PCR?

PCR uses Taq polymerase, which only acts on DNA, so reverse transcriptase first converts RNA → complementary DNA (cDNA).

Why can’t RT-PCR be used for all viruses?

Not all viruses have RNA genomes; some are DNA viruses. Also, probes/primers specific to viral RNA may not exist.

How to extend a biological investigation?

Add new measurable variables (e.g. test for enzymes or anatomy), increase sample size, and alter controlled variables to assess effect.

How do you structure an ethical discussion response?

1⃣ Identify ethical concern
2⃣ Explain effect/consequence
3⃣ Propose feasible solution
4⃣ Link to ethical concept (justice, beneficence, etc.)

What are the major types of gene mutations and their outcomes?

• Frameshift (insertion/deletion): shifts reading frame → faulty protein

• Nonsense: introduces premature stop codon

What must be mentioned when describing ethanol production by microbes?

Always state anaerobic fermentation (no O₂) of glucose → ethanol + CO₂, carried out by yeast or bacteria.

Why do we need new vaccines yearly for influenza?

Antigenic shift/drift alters viral surface proteins → old memory cells no longer recognise virus → new vaccine needed to produce new antibodies.

Why do vaccinated people usually show only mild symptoms?

Memory B and T cells rapidly activate → quick, large antibody response → virus neutralised before severe infection develops.

What must always be included in any speciation explanation?

• Type (allopatric/sympatric)

• Barrier preventing gene flow (geographic/reproductive)

• Selection pressures in each environment

• Accumulation of genetic differences → new species

How to describe trends in brain and limb evolution?

• Brain: increased cranial capacity → larger brain

• Limbs: increased leg-to-arm ratio, inward femur angle → supports bipedalism

What common limitations reduce reliability of evolutionary evidence?

• Incomplete fossil record

• Lack of specific location or context

• Uncertain molecular data or missing sequences