Speciation
This lesson covers:
- Who Alfred Russel Wallace was
- What a species is
- How a new species can arise - 'speciation'
Alfred Russel Wallace
Like Darwin, Alfred Russel Wallace was a scientist, who after travelling around the world and collecting evidence, proposed a theory of evolution based on the process of natural selection.
Darwin and Wallace knew of each other, and decided to present their scientific findings together in 1858. This prompted Darwin to publish the book 'On the Origin of Species' the following year, which made him famous and is why he is still regarded as the one who discovered evolution.
Wallace is best known for two things:
1Studying warning colouration in animals, for example in the Golden Birdwing Butterfly.
2His theory of speciation.
Speciation 1A species is defined as a group of genetically similar organisms that are able to interbreed and produce fertile offspring. |
2Speciation means the formation of a new species. This can happen when different populations of the same species become so different that they are unable to interbreed and produce fertile offspring anymore, at which point they are considered different species and we say speciation has occurred. |
Speciation may occur due to a combination of both isolation, and natural selection. Isolation happens when a physical barrier (such a new river or mountain range) separates two different populations of a given species.  The environment may be different on either side of the barrier. For example the climate or food sources on either side of a mountain range may be different. |
Because the populations on either side of the barrier now live in different environments, the two populations experience different selection pressures. This means that different traits become more favourable in each population, and through the process of natural selection, different characteristics will become more common in the two populations. |
After a long time (many generations), the two populations become so different from each other (genetically / physically / behaviourally) that they will no longer be able to interbreed and produce fertile offspring. At this point speciation has occurred, and the two populations are separate species. |
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Which scientist nearly published his findings on speciation before Charles Darwin?
Alfred Russel Wallace
Richard Dawkins
Charles Dickens
James Cook
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What is a species?
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One of the main ways new species arise is when populations become from each other.
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Charles Darwin and Alfred Russel Wallace, both proposed the theory of evolution by natural .
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Explain how two different species of rabbit could have developed from a common ancestor.
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