NCEA 91603: plant and animal responses to the environment (Level 3 Biology)

What NCEA 91603 assesses

NZQA's standard says the responses are selected from four groups, and that the external environment includes both biotic and abiotic factors:

• Orientation in space: tropisms, nastic responses, taxes, kineses, homing and migration.
• Orientation in time: annual, daily, lunar and tidal rhythms.
• Interspecific relationships: competition, mutualism, and exploitation including herbivory, predation and parasitism.
• Intraspecific relationships: competition, territoriality, hierarchical behaviour, cooperative interactions and reproductive behaviours.

Achieved describes the process within each response, or the adaptive advantage it gives the organism in its ecological niche. Merit uses biological ideas to explain how the responses occur and why they give an advantage. Excellence links biological ideas to explain why the responses give an advantage, which may involve justifying, relating, evaluating, comparing and contrasting, and analysing.

The NCEA 91603 exam in 2026 and 2027

NCEA 91603 is one of three Level 3 Biology externals, with 91605 and 91606. The 2026 exam is on Tuesday 17 November, in the afternoon session. NZQA's 2027 timetable is not out yet: it says exams run from 9 November to 3 December 2027. The 2026 and 2027 specifications say papers contain resource-based questions, you should be familiar with graphical and tabulated data, and you may use annotated diagrams. They list terms to know, such as phytochrome, auxin, abscisic acid, actograms, zeitgebers, entrainment, home range, kin selection and agonistic behaviour. The 2027 list adds mimicry, allelopathy and reproductive strategies.

How NCEA 91603 is marked: grade score marking

Each question scores N0 to E8 and the three add to 24. Four distinct points at Achievement reach A4, so one well-organised paragraph per response matters more than length.

NCEA 91603 cut scores

These are NZQA's cut scores for the total out of 24, taken from each year's assessment schedule. Over these five years Achieved needed 8 in every year but one (9 in 2023), Merit 14 and Excellence 19. The 2026 cut scores will appear in NZQA's 2026 schedule once the exam has been marked.

Worked examples at each grade

Achieved: describe a response

Describe how a plant shoot grows towards light. The shoot tip makes auxin, which moves to the shaded side. Cells on that flank lengthen more than those facing the light source, so the shoot curves towards it. This is positive phototropism.

Merit: explain how and why

Explain how a short-day plant flowers in autumn, and why this helps it. A short-day plant responds to the length of the uninterrupted night, not the day. Phytochrome exists as two forms, Pr and Pfr. Light converts Pr to Pfr, and Pfr slowly reverts to Pr in the dark. When nights are long enough, Pfr falls low enough to trigger flowering. This ties flowering to the time of year, so flowers open when pollinators are active and seeds can mature before winter, which increases the plant's reproductive success.

Excellence: link and compare

Compare how photoperiod controls breeding in a sheep and in a long-day bird, and evaluate the advantage. Both measure day length. In sheep, which are short-day breeders, the longer autumn nights lengthen melatonin release and trigger breeding. Gestation takes about five months, so lambs arrive in spring when food is abundant. In a long-day bird, lengthening spring days trigger breeding, and the short egg and nestling period means young hatch in the food-rich summer. The same cue produces opposite responses because each response is tuned to the species' own gestation or incubation time, so offspring arrive when survival is most likely.

Excellence answers link the mechanism to survival and reproductive success. Check one idea with a question on the page:

Exam answers

The answers and a worked mark scheme come with today's paper once it is marked. We do not publish official or past paper answers. Every question on the daily paper is our own.

Use the daily paper as a practice exam

Uni-Sine publishes a free daily paper on the NCEA Level 3 Biology track. It is a short timed paper of 8 questions worth 25 to 35 marks, not a full NCEA exam, and it is not written by NZQA. Only a few of its questions are on stimuli and responses, so use it for exam practice and write your own long answers on the four response groups. See the NCEA Level 3 Biology guide for the whole subject.

Common mistakes in NCEA 91603

NZQA's 2025 report on Level 3 Biology says candidates who were awarded Merit often:

• Explained each response alone. They did not link them together or relate them to greater reproductive success.
• Stopped at the mechanism. For example they explained why the poinsettia is a short-day plant but not how growers manipulate flowering out of season.
• Missed kin selection. They described living in a pack but not its significance.
• Left out the big picture. The report says candidates should address the stem and all the bullet points of each question, attempt all three questions, and write legibly.

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New Zealand · NCEA Level 3NCEA Level 3 Biology: standards, exam date and practiceNCEA Level 3 Biology explained: externals on responses to the environment, speciation and human evolution, the internals, the 2026 exam date and examples.