6.2 Speciation

Question 1

What is Wallace best known for? (2)

Answer 1

• Studying warning colouration in animals, for example in the Golden Birdwing Butterfly.
• His theory of speciation

Question 2

Speciation

Answer 2

• Speciation 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 as 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, 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.

Question 3

What is a species

Answer 3

A species is a group of organisms that are able to interbreed and produce fertile offspring.