To understand how new species can arise 3. The morphological species concept vs. the biological species concept In the Modern Synthesis, the criteria for deciding whether 2 individuals are in the same or different species must be stated in terms of population genetics. A geographical barrier splits the range of a species into 2, preventing gene flow. The 2 sub-populations diverge genetically. Allopatric speciation is especially common on island chains.
Sympatric speciation Occurs without geographical barriers.
It can also occur in plants via polyploidy . This is the mechanism that has produced many of our grain crops, e.g. , modern corn and wheat. The fossil record suggests that new species may arise relativly quickly, at least in some cases.