Evolutionary processes leading to speciation

Practice

Recall it first, then use it — testing yourself builds the memory, where rereading the notes above only feels easier.

Recall and application shuffled together — you have to work out what each item wants before you can answer it, which is the part the exam actually tests. Both kinds feed the same spacing schedule, so anything you miss comes back sooner.

Say the answer out loud before flipping — that attempt is where the learning happens, even when you get it wrong.

Exam-style only. Instant feedback, shuffled each attempt, best score saved on this device.

What actually comes up

Three extended "Discuss" questions every year, each built around a real (often NZ-native) species or species pair. The topics rotate — reproductive isolation, convergent vs divergent evolution, allopatric vs sympatric speciation, adaptive radiation, gradualism vs punctuated equilibrium — but the shape of each answer is the same: define the key terms, apply TWO named mechanisms to the specific organisms in the resource, and finish with a judgement the resource's own evidence supports.

Across 4 years

The pattern — what to prepare

The 2022 paper ↗ Marking schedule ↗

Question One — Poison (TTX in newts, pufferfish, and the blue-ringed octopus)

Tetrodotoxin (TTX) is used as an antipredator defence by newts, pufferfish and the blue-ringed octopus independently. Some snakes (e.g. the garter snake) have evolved TTX resistance through changes to protein-coding genes, and a survey showed a range of snake-population "performance scores" against varying newt TTX levels.

• describe Define coevolution, convergent evolution, and mutation. Achieved
• explain Explain how the octopus, pufferfish and newt each having TTX is an example of convergent evolution. Merit
• discuss Using data from the graph, discuss how coevolution has led to an increase in TTX production in newts, and evaluate the implications for the survival and success of the newt species. Excellence

Question Two — New Zealand triplefin fish

Over 20 species of triplefin are endemic to New Zealand, occupying different zones of the shore, out of roughly 130 species worldwide.

• describe Describe what is meant by the terms endemic and species. Achieved
• explain Explain how temperature may act as a selection pressure, leading to different triplefin species being found at different zones of the beach. Merit
• discuss Discuss how the process of natural selection has resulted in such a large number of triplefin species. Excellence

Question Three — Polyploidy in kūmara, tī pore, and uwhi

Polyploidy is inferred in the origins of kūmara, tī pore and uwhi, three crops brought to New Zealand by Māori from tropical Polynesia around AD 1250.

• describe Define polyploid and reproductive isolation. Achieved
• explain Explain how polyploids are formed. Merit
• discuss Discuss how polyploidy is an example of sympatric speciation, and explain how two other reproductive isolating mechanisms could have contributed to the speciation of kūmara, tī pore, and uwhi. Excellence

The 2025 paper ↗ Marking schedule ↗

Question One — The apple maggot fly and the hawthorn fly

R. pomonella, native to North America, originally laid eggs only on hawthorn fruit. ~200 years ago apples arrived, and the species split into an apple maggot group and a hawthorn group — physically similar, no geographic separation, still classified as one species. Apples ripen earlier so apple flies emerge earlier; the two groups differ in enzymes and in larval development time (~40 days in apples vs 55–60 days in hawthorn fruit).

• describe Describe speciation and reproductive isolating mechanisms, including definitions. Achieved
• explain Explain how TWO named isolating mechanisms may have caused the formation of the two groups of fly. Merit
• discuss Discuss a suggestion as to why the two groups are not yet considered separate species. Excellence

Question Two — Lamprey and eels

Adult lampreys and eels look similar despite being separate species for millions of years (long flexible body, undulating swimming, no paired fins, mucus-covered, tolerant of low oxygen), but differ in skeleton, jaw, fins, gill structure, scales, and life cycle.

• describe Describe convergent evolution and an analogous structure. Achieved
• explain Explain how TWO named selection pressures influenced the similarities between lamprey and eel. Merit
• discuss Discuss TWO examples of scientific evidence that show the similarities are convergent, not divergent, evolution. Excellence

Question Three — Tetraploid treefrogs

The gray treefrog (tetraploid, 4N) and Cope's gray treefrog (diploid, 2N) are physically identical but distinguished by mating call and chromosome number; the tetraploid species is thought to have evolved through multiple hybridisation events from diploid ancestors, and the two species share habitat but do not interbreed.

• describe Describe hybridisation and polyploidy, including definitions. Achieved
• explain Explain how polyploidy can produce hybrid frogs. Merit
• discuss Discuss why this is an example of sympatric (not allopatric) speciation, and why it is an example of punctuated equilibrium (not gradualism). Excellence

The 2024 paper ↗ Marking schedule ↗

Question One — Kōura

Kōura (freshwater crayfish) often live in small, inbred populations. mtDNA reveals three genetically distinct groups (West Coast, southern, northern) despite only two named species, thought to have diverged around the time the Southern Alps formed. Genetic diversity is low WITHIN populations but high BETWEEN them; Māori historically moved kōura between areas, which helped population success.

• describe Describe the terms founder population and gene flow. Achieved
• explain Explain how the formation of the Southern Alps may have helped lead to divergent evolution by allopatric speciation. Merit
• discuss Discuss why moving kōura between areas prevents speciation. Excellence

Question Two — Wallabies on Kawau Island

Tammar and parma wallabies are allopatric in Australia with different habitat use, social structure, and mating times. Both were introduced to Kawau Island, New Zealand, in the late 19th century, where they now live sympatrically with no genetic evidence of hybridisation.

• describe Describe the terms sympatric and species, including definitions. Achieved
• explain Explain the rate of evolution shown in the phylogeny (gradualism or punctuated equilibrium), and why adaptive radiation is seen in the wallabies in Australia but not in New Zealand. Merit
• discuss Discuss TWO reproductive isolating mechanisms that may keep the wallabies from hybridising despite being sympatric on Kawau Island. Excellence

Question Three — A case of convergent evolution

Flight has evolved independently in many animal groups. Honeybee wings (not made of bone) and bird wings serve the same function via different muscle attachments and different lift mechanisms, but the shared demands of flight produce distinct similarities.

• describe Describe selection pressures, including descriptions with examples. Achieved
• explain Explain how genetic data is used to show convergent evolution. Merit
• discuss Discuss how the process of natural selection has resulted in analogous structures. Excellence

The 2023 paper ↗ Marking schedule ↗

Question One — Kākāpō genetic diversity

The flightless kākāpō is down to around 250 individuals, most descended from an isolated island gene pool. Present-day island kākāpō carry fewer harmful mutations than mainland kākāpō, possibly through natural selection removing them over time.

• describe Describe the terms mutation and gene pool, including definitions. Achieved
• explain Explain how the founder effect enables genetic drift to be more apparent in the kākāpō species. Merit
• discuss Discuss how genetic drift and natural selection may have implications for the survival of the species. Excellence

Question Two — Coprosma

Coprosma (mingimingi), around 90 species of flowering plant, originated in New Zealand over 25 million years ago and is now found across Hawaii, Australia, and the Pacific, growing as shrubs, small trees, or mat-like forms across a wide range of habitats.

• describe Describe adaptive radiation and niche, including definitions. Achieved
• explain Explain how different habitats have led to adaptive radiation of Coprosma. Merit
• discuss Discuss why Coprosma growing on different islands might have different appearances and can be classed as different species. Excellence

Question Three — Peripatus / ngāokeoke, the velvet worm

Of roughly 30 NZ velvet worm species, only 9 are clearly identified. Peripatoides (ovoviviparous, live young) tend to live in warmer, enclosed, lower-altitude habitats; Ooperipatellus (oviparous, egg-laying, found only in NZ and Australia) tend to live in colder, more open, higher-altitude habitats.

• describe Describe allopatric speciation and sympatric speciation, including definitions. Achieved
• explain Explain how geological processes might give rise to increased speciation in the New Zealand velvet worm, and why DNA analysis might lead to the discovery of new species. Merit
• discuss Discuss how TWO named reproductive isolating mechanisms could ensure the worms do not form hybrids. Excellence

Grades above are the schedule's own Describes/Explains/Discusses columns condensed to their essentials — the real cut is holistic across all three questions (roughly 8/13/18 of 24 marks), not a fixed mark per bullet.

Past exams & resources

⏱ Timed opens the paper and starts a countdown matching the exam length. Official NZQA PDFs. If a link 404s, that year’s paper may sit under a slightly different code: browse the NZQA subject page.