Every term here is named in the NZQA 2026 assessment specification as one candidates should be familiar with. Resource-based questions lean on them heavily — especially reading a phylogenetic tree and naming the geological event that split a population.
📖 Required terms: molecular evidence and phylogeny
5 terms
Mitochondrial DNA (mtDNA)
DNA in the mitochondria. Inherited from the mother only, does not recombine, and mutates faster than nuclear DNA. Best for tracing recent divergence and maternal lineages — the fast clock.
Nuclear DNA (nDNA)
DNA in the nucleus. Inherited from both parents, recombines each generation, and mutates more slowly. Best for deeper, older relationships, and it captures both parental histories.
Phylogeny
The evolutionary history of a group — who descended from whom — usually drawn as a phylogenetic tree. Branch points are common ancestors. Closeness on the page means nothing; what matters is where lineages join.
Clade
A common ancestor plus every one of its descendants — a complete branch cut from the tree. If a group leaves out some descendants of its ancestor, it is not a clade.
Ring species
A chain of neighbouring populations that can each interbreed with the next, but where the two ends of the ring cannot interbreed where they overlap. Speciation caught in the act: it shows the boundary between “variety” and “species” is a continuum, not a line.
Choosing mtDNA or nDNA in an answer
Asked about a recent split, or a maternal line? Use mtDNA — it mutates faster so it accumulates differences quickly, and it is not scrambled by recombination.
Asked about deep relationships, or you need both parents’ history? Use nDNA.
More differences in the sequence → longer since the two lineages shared a common ancestor. That is the whole logic of a molecular clock.
mtDNA cannot detect a male-only contribution — a standard limitation worth stating for Excellence.
Geological events that drive speciation (all named in the specification)
Event
What it does
Effect on populations
Tectonic movement
Continents and plates drift apart or collide
Splits a once-continuous population — classic allopatric speciation
Orogeny (mountain building)
Raises a mountain range
A new physical barrier; also creates new altitudes and habitats to radiate into
Glaciation
Ice sheets advance and retreat
Isolates populations in ice-free refugia, then lets them meet again — a repeated split-and-rejoin cycle
Sea level change
Flooding or exposing land bridges
Islands separate populations when levels rise; land bridges reconnect them when levels fall
✓
The move examiners are looking for
A resource will describe a landscape or a date, and expect you to name the geological event and say it caused geographic isolation, then run the usual chain: isolation → no gene flow → different selection pressures and drift act on each population → genetic differences accumulate → reproductive isolation → separate species. Naming the event without the isolation step is only half the answer. ✕
Reading a phylogenetic tree
Two tips drawn next to each other are not necessarily closely related — the branches can be rotated at any node without changing the meaning. What matters is how recently their lineages join. Trace back to the shared node: the more recent the node, the closer the relationship.