← Evolutionary processes leading to speciation
1 Reading the notation
This standard is definition-heavy. Precise wording separates Merit from Excellence: learn these exactly.📖 Key definitions: Evolution & speciation (91605)
24 termsCover the right column and recite each one.
- Evolution
- A change in the allele frequencies of a population’s gene pool over successive generations. Populations evolve: individuals do not.
- Gene pool
- All of the alleles of all the genes present in a breeding population at a given time.
- Allele frequency
- The proportion of a particular allele among all alleles of that gene in a population.
- Mutation
- A random change in the DNA base sequence: the ultimate source of all new alleles.
- Natural selection
- The process by which individuals with favourable heritable variations survive and reproduce more successfully, increasing the frequency of those alleles.
- Genetic drift
- A random change in allele frequencies due to chance, most significant in small populations. Non-adaptive: unlike natural selection.
- Bottleneck effect
- A sharp reduction in population size (e.g. by a catastrophe) that leaves a surviving gene pool with reduced genetic diversity.
- Founder effect
- The reduced genetic diversity that results when a new population is established by a small number of individuals carrying only a sample of the original gene pool.
- Gene flow
- The movement of alleles between populations via migration and interbreeding. It makes populations more genetically similar.
- Species
- A group of organisms that can interbreed to produce fertile, viable offspring.
- Speciation
- The formation of a new species from an existing one, occurring when populations become reproductively isolated.
- Allopatric speciation
- Speciation caused by a geographical barrier physically separating populations and preventing gene flow.
- Sympatric speciation
- Speciation occurring without geographical separation, e.g. by polyploidy or exploiting different niches.
- Reproductive isolation
- Any mechanism that prevents two populations from interbreeding successfully.
- Pre-zygotic mechanism
- An isolating mechanism that prevents a zygote from forming (temporal, ecological, behavioural, mechanical, gametic).
- Post-zygotic mechanism
- An isolating mechanism acting after fertilisation. The hybrid is inviable, sterile, or its offspring break down.
- Directional selection
- Selection favouring one extreme phenotype, shifting the population mean toward it.
- Stabilising selection
- Selection favouring the intermediate phenotype and acting against both extremes.
- Disruptive selection
- Selection favouring both extreme phenotypes over the intermediate: can split a population.
- Divergent evolution
- Related species becoming increasingly different over time, producing homologous structures.
- Convergent evolution
- Unrelated species evolving similar features under similar selection pressures, producing analogous structures.
- Coevolution
- Two or more species evolving in response to each other (e.g. flower and pollinator).
- Adaptive radiation
- The rapid diversification of one ancestral species into many species occupying different niches.
- Punctuated equilibrium
- A pattern of long periods of little change (stasis) interrupted by short bursts of rapid evolutionary change.
Related elsewhere
Study skills: NZQA command words Biology grades hinge on the command word: “describe” wants what happens, “explain” wants why, and “discuss/evaluate” wants a judgement. A precise definition plus the right depth for the verb is most of the difference between Achieved and Excellence here.Practice for this standard covers the whole topic — flashcards and quiz.