Speciation (biology only) — AQA GCSE Biology
Test yourself on Speciation (biology only) with AQA GCSE practice questions.
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Speciation (biology only) explained
Darwin and Wallace both gathered evidence that living things change over time.
Read the full explanation
Darwin studied fossils, Galapagos finches and artificial selection by breeders. Wallace studied wildlife in South America and South-East Asia and independently reached the same mechanism. Both proposed that individuals with inherited variations better suited to their environment are more likely to survive, reproduce and pass on those alleles, so the population changes over generations. Their work gave biology a unifying explanation for adaptation, biodiversity and the fossil record. It also prompted questions about the age of the Earth and the place of humans in nature, shaping modern genetics, ecology and medicine.
Alfred Russel Wallace independently proposed the theory of evolution by natural selection.
Wallace reached the same conclusion as Darwin without seeing Darwin's unpublished work. While collecting specimens in the Malay Archipelago, he noticed that closely related species often lived in nearby but separate areas, and that each area had species suited to local conditions. He sent Darwin an essay in 1858 outlining natural selection. This showed that the mechanism was not a one-off insight but could be worked out from evidence. Wallace's fieldwork also contributed to ideas about geographical distribution and warning colouration. His independence strengthened the theory because two naturalists using different evidence reached the same explanation.
He published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year.
In 1858 Wallace sent Darwin an essay containing the idea of natural selection. Friends arranged for extracts from Wallace's essay and from Darwin's unpublished work to be read together at the Linnean Society in London. This joint communication established that both men had reached the same conclusion. It also pushed Darwin to finish and publish his book On the Origin of Species in 1859. The book set out the evidence and the mechanism in detail, reaching a wide audience and changing biology. The sequence shows how scientific ideas are shared, checked and published, and why priority and collaboration matter in science.
Wallace worked worldwide gathering evidence for evolutionary theory.
Alfred Russel Wallace was a British naturalist who independently developed ideas about evolution by natural selection. Unlike Darwin, who largely worked from his Beagle collections and British observations, Wallace travelled extensively across South America and the Malay Archipelago, collecting thousands of specimens and recording where each was found. This worldwide fieldwork gave him evidence that species vary geographically and that similar species often live in neighbouring regions. For example, his observations of animals on separate islands helped him link variation, isolation and the formation of new species. His letters to Darwin prompted the joint presentation of their ideas in 1858. Students should understand that Wallace's contribution was not a single discovery but a large body of global evidence that supported and refined evolutionary theory.
He is best known for his work on warning colouration in animals and his theory of speciation.
Wallace is particularly remembered for two connected areas of work. First, he studied warning colouration, where prey animals have bright, conspicuous patterns that predators learn to avoid because the prey is toxic or dangerous. He also described mimicry, where a harmless species resembles a warningly coloured species and gains protection. Second, he developed ideas about speciation: populations that become separated can accumulate different variations, and over many generations they may become so different that they can no longer interbreed to produce fertile offspring. His island observations supported this because related species on different islands showed distinct features. Students should be able to explain both the warning colouration idea and the role of isolation and selection in forming new species, using examples such as brightly coloured frogs or insects.
Alfred Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation.
Wallace's work on speciation was pioneering because he linked geographical isolation, variation and natural selection to the formation of new species at a time when these ideas were new. However, science is self-correcting: later evidence from genetics, DNA sequencing, fossils, biogeography and laboratory studies has refined and strengthened the theory. For example, modern genetics explains how mutations create new alleles and how reproductive isolation can arise through changes in mating behaviour, chromosomes or fertility. Students should recognise that Wallace's conclusions were largely correct but incomplete, and that the current theory of speciation is supported by a much wider range of evidence than was available in the nineteenth century. This shows how scientific explanations develop as new evidence accumulates.
Students should be able to describe the steps which give rise to new species.
Speciation is the formation of new species from existing populations. The process begins with variation: individuals in a population differ because of mutations and sexual reproduction. If part of the population becomes geographically or reproductively isolated, for example by a river, mountain range or island colonisation, the two groups can no longer interbreed freely. Each group experiences different selection pressures, so different alleles are favoured. Over many generations, natural selection changes the allele frequencies in each population. Eventually the groups become so genetically different that they cannot interbreed to produce fertile offspring, which means they are now separate species. Students should be able to sequence these steps clearly and use the term reproductive isolation accurately.
Your focus
- Describe the contributions of Darwin and Wallace to the theory of evolution by natural selection.
- Explain how natural selection produces evolutionary change in populations.
- Explain the impact of evolutionary ideas on biology, including adaptation and biodiversity.
Show all 21 objectives
- State that Wallace independently proposed evolution by natural selection.
- Describe evidence from Wallace's fieldwork that supported natural selection.
- Explain why independent discovery by Wallace strengthened the theory.
- State the year of the joint writings and the year On the Origin of Species was published.
- Explain how the joint writings prompted Darwin to publish his book.
- Describe how publication helped establish the theory of evolution by natural selection.
- State where Wallace travelled and what he collected.
- Explain how worldwide evidence supported evolutionary theory.
- Link Wallace's observations to variation and the formation of new species.
- Describe how warning colouration protects an organism from predators.
- Explain the role of isolation and selection in speciation.
- Distinguish between warning colouration, camouflage and mimicry.
- Describe Wallace's pioneering contribution to the theory of speciation.
- Explain how later evidence has refined the theory of speciation.
- Discuss why scientific theories can change as new evidence emerges.
- List the main steps that lead to speciation.
- Explain how isolation and natural selection cause populations to diverge.
- Define a species in terms of interbreeding and fertile offspring.
Speciation (biology only) exam tips
Marking Points
- Describe Darwin's evidence from fossils, island species and artificial selection by breeders.
- Describe Wallace's independent work on variation and survival in different geographical regions.
- Explain natural selection as survival and reproduction of individuals with advantageous inherited variations.
- Explain that the ideas changed biology by providing a mechanism for evolution and a unifying explanation for adaptation and biodiversity.
- Recognise that the work was published jointly and that it challenged accepted religious and scientific views of the time.
- State that Wallace developed the idea of natural selection independently of Darwin.
- Describe Wallace's fieldwork in South America and South-East Asia as a source of evidence.
- Explain that Wallace observed variation and adaptation in species living in different regions.
- Explain that his essay sent to Darwin in 1858 described the same mechanism.
- Recognise that independent discovery strengthened confidence in the theory.
- State that joint writings by Darwin and Wallace were published in 1858.
- Explain that the joint publication presented natural selection to the scientific community.
- State that Darwin then published On the Origin of Species in 1859.
- Explain that the book provided detailed evidence and made the theory widely known.
- Recognise that publication and peer discussion are part of how scientific ideas are validated.
- Wallace travelled widely, including in South America and the Malay Archipelago, rather than working only in one country.
- He collected many specimens and recorded detailed information about where each organism was found.
- His worldwide observations showed that closely related species often occupy neighbouring geographical areas.
- He used patterns in variation and distribution to support the idea that species change over time.
- His evidence contributed to the development of evolutionary theory alongside Darwin's work.
- He recognised that geographical isolation could allow populations to diverge into new species.
- Warning colouration makes a toxic or dangerous organism conspicuous to predators.
- Predators learn to associate the bright pattern with an unpleasant experience and avoid similar prey.
- Mimicry occurs when a harmless species resembles a warningly coloured species and gains protection.
- Speciation involves populations becoming reproductively isolated so that gene flow between them stops.
- Different selection pressures in separated environments cause different variations to be favoured.
- Over many generations the separated populations become sufficiently different to be classified as different species.
- Wallace produced pioneering ideas about how new species form through isolation and natural selection.
- His work was limited by the evidence and techniques available in his lifetime.
- Later evidence from genetics and DNA sequencing has explained how variation and reproductive isolation arise.
- Fossil and biogeographical evidence has supported and extended the theory of speciation.
- The current theory is stronger because it is supported by multiple independent lines of evidence.
- Scientific theories are revised and refined as new evidence is collected, rather than remaining fixed.
- Variation exists within a population due to mutations and sexual reproduction.
- Populations can become isolated by geographical barriers or other mechanisms that prevent interbreeding.
- Different selection pressures act on the separated populations.
- Individuals with advantageous alleles are more likely to survive and reproduce, passing on those alleles.
- Allele frequencies change over many generations in each population.
- The populations become reproductively isolated and can no longer produce fertile offspring, forming new species.
Examiner Tips
- 💡Name both scientists and give at least one distinct piece of evidence each used.
- 💡Use the phrase 'inherited variation' and link it to survival, reproduction and passing on alleles.
- 💡When explaining impact, refer to biology as a whole, such as providing a mechanism for evolution or explaining biodiversity.
- 💡Use the word 'independently' to show you know Wallace was not working from Darwin's notes.
- 💡Give one concrete detail of Wallace's fieldwork, such as his travels in the Malay Archipelago.
- 💡Link his proposal to the same mechanism as Darwin: inherited variation, survival and reproduction.
- 💡Keep the two dates distinct: 1858 for the joint writings and 1859 for On the Origin of Species.
- 💡Use the phrase 'prompted Darwin to publish' to show the causal link.
- 💡Mention the Linnean Society or joint reading only if you are confident; the key point is joint publication in 1858.
- 💡Name specific regions such as South America or the Malay Archipelago to show precise knowledge rather than saying only that he travelled.
- 💡Link Wallace's worldwide evidence to the idea that species vary and can change, rather than listing places without explanation.
- 💡Use phrases such as gathered evidence and supported evolutionary theory to keep answers focused on the specification statement.
- 💡Use the term reproductive isolation and explain that the populations can no longer interbreed to produce fertile offspring.
- 💡When describing warning colouration, state the benefit to the prey and the learning response of the predator.
- 💡Keep the example brief and relevant, such as a brightly coloured toxic frog, rather than writing a long story.
- 💡Use the phrase more evidence over time to show how the theory developed rather than implying Wallace was simply mistaken.
- 💡Give at least one type of later evidence, such as DNA sequencing or fossil evidence, to support your explanation.
- 💡Link the development of the theory to the idea that science is based on evidence and is open to revision.
- 💡Write the steps in a logical sequence: variation, isolation, selection, change in allele frequency, reproductive isolation.
- 💡Use the phrase cannot interbreed to produce fertile offspring when defining a new species.
- 💡Refer to allele frequencies changing in populations rather than saying individuals change.
Common Mistakes
- Saying Darwin and Wallace invented evolution; correct this by stating they proposed natural selection as the mechanism, while earlier thinkers had already suggested that species change.
- Describing natural selection as organisms choosing to adapt; correct this by explaining that variation already exists and the environment selects which individuals survive and reproduce.
- Treating Darwin and Wallace as rivals who worked separately; correct this by noting they communicated and published joint writings in 1858.
- Claiming Wallace copied Darwin's idea; correct this by stating he worked independently and sent his essay to Darwin.
- Confusing Wallace with Lamarck; correct this by noting Wallace proposed natural selection, not inheritance of acquired characteristics.
- Saying Wallace only studied birds; correct this by referring more broadly to his work on variation, adaptation and geographical distribution.
- Saying Darwin published On the Origin of Species in 1858; correct this by giving 1859 for the book and 1858 for the joint writings.
- Thinking Wallace published the book alone; correct this by stating the book was Darwin's, prompted by the joint communication.
- Believing the joint writings were a full book; correct this by describing them as a joint communication of their ideas.
- Thinking Wallace worked only in Britain or only with fossils; correction: he gathered evidence through worldwide fieldwork on living organisms.
- Confusing Wallace with Lamarck or claiming Wallace invented natural selection alone; correction: Wallace independently reached similar conclusions to Darwin and they presented their ideas jointly.
- Assuming Wallace's evidence was purely theoretical with no specimens; correction: his conclusions were based on extensive collecting and recording of real organisms.
- Confusing warning colouration with camouflage; correction: warning colouration is conspicuous and advertises danger, whereas camouflage helps an organism blend in.
- Thinking speciation happens in a single generation; correction: speciation requires many generations of variation, selection and reproductive isolation.
- Believing that isolation alone creates new species; correction: isolation must be followed by different selection pressures and genetic changes over time.
- Claiming Wallace's theory was completely wrong; correction: his core ideas were pioneering and broadly supported, but later evidence refined them.
- Thinking the current theory of speciation came only from Wallace; correction: it developed from many scientists and many types of evidence over time.
- Assuming scientific theories never change; correction: theories are updated when new evidence requires revision.
- Saying an individual organism evolves; correction: populations evolve as allele frequencies change over generations.
- Thinking isolation alone causes speciation; correction: isolation must be followed by different selection pressures and genetic change over many generations.
- Confusing a new species with a new variety; correction: a new species is reproductively isolated and cannot produce fertile offspring with the original population.