A4.1 Evolution & speciation - written task
This structured question is in the style of IB exam questions, with a focus on the concept of speciation.
Speciation is the splitting of one species into two separate species.
This occurs when two populations of a single species become isolated, evolve independently and eventually are unable to reproduce together.
If two wild populations never have the opportunity to breed together the decision to classify them as two different species can be rather arbitrary. Are they simply two separate populations of the same species or actually two separate species.
The Milos viper (Macrovipera lebetinus schweizeri) lives on Milos, one of the Cycladic islands in the Aegean sea. It is a sub-species of the blunt-nosed viper (Macrovipera lebetinus) found in mainland Greece.
"Sub-species", is a term used by biologists for populations that live in different areas, vary in physical characteristics, but can successfully interbreed.
Some scientists believe that the Milos viper should be classified as a separate species. Others claim it is a sub-species, an example of gradual evolutionary change in two populations of a species but not (yet) speciation.
Explain the importance of reproductive isolation in the process of speciation.
(2 marks)
One mark for describing reproductive isolation.
One mark for explaining the consequence on speciation.
Explain how differential selection pressures can lead to divergent evolution.
(3 marks)
One mark for describing selection pressure, and one for divergent evolution.
One or two for explain the connection / process.
Outline the role of mutation in evolution.
(3 marks)
One mark for explaining how a mutation affects the traits of an organism,
One mark for the importance of variation in evolution.
One or two marks for explaining the process, of natural selection, and survival of the fittest.
Explain how polyploidy can abruptly cause speciation.
(2 marks)
Each response must be linked to speciation.
Scientific name is not required.
Suggest how Macrovipera lebetinus schweizeri could have evolved to become a separate sub species from the mainland Macrovipera lebetinus
Teachers note - suggest requires the use of biological knowledge and concepts.
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