Look at the photos and think about the difference between the flowers. The following information is presented in a slightly different way than it is presented in your text. Allopatric speciation takes place when two populations are geographically isolated. The figure 14.1 shows a way in which allopatric speciation might happen. This form of speciation can happen with all life forms.
Sympatric speciation occurs within a population, without geographic isolation.
This may be common among some insects and animal parasites. Polyploid individuals in a population are often unable to interbreed with normal individuals, and so even though there is no geographic barrier to genetic interchange, there is a biological one. This is most common in plants. Now, I'd like to comment on the statement on page 321 about endemic species . A disjunct is a taxon whose range is geographically isolated from that of its closest relatives.