AQA GCSE Biology

Revision Notes

6.3.2 Speciation

Darwin & Wallace

  • Alfred Russel Wallace was a scientist who, after conducting his own travels around the world and gathering much evidence, independently developed his own theory of evolution based on the process of natural selection
  • He published scientific papers on this theory with Darwin in 1858 (Darwin published his book, On the Origin of Species, the following year
  • Wallace is best known for:
    • His work studying the warning colouration of species (particularly butterflies) and how this must be an example of a beneficial characteristic that had evolved by natural selection, as the warning colouration helps to deter predators
    • Developing the theory of speciation

Speciation

  • Alfred Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation
  • Speciation is a process that results in the formation of a new species
  • When populations of the same species become so different that they are unable to interbreed and produce fertile offspring, they are considered different species and speciation has occurred
  • Speciation can occur as a result of a combination of isolation (when populations of the same species become separated) and natural selection:
    • Populations of the same species can become isolated from one another due to the formation of a physical barrier (eg. a new river or mountain range) – this is known as geographic isolation
    • The environment will be different on either side of this physical barrier (eg. different climates or different food available)
    • The environmental differences on either side will provide different selection pressures and natural selection will cause a different set of characteristics to become more common in the two isolated populations
    • Over many generations, individuals from the two populations will have become so distinct (genetically, behaviorally, physically) that they will no longer be able to interbreed and produce fertile offspring
    • The two populations are now separate species

Speciation, downloadable IGCSE & GCSE Biology revision notes

The process of speciation

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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