Reproductive isolation reduces gene flow, allowing populations to diverge. Geographic separation and different selection pressures can drive speciation; chimpanzees and bonobos illustrate river-linked isolation and divergence.
The confirmation of DNA as the genetic material, together with the elucidation of its structure by Crick and Watson, had a profound effect on modern biology.
Explain how isolation leads to speciation.
| a | speciation is a new species forming from an existing species/splitting of a species; |
| b | speciation depends on reproductive isolation/no interbreeding between populations; |
| c | gene pools of populations are separate/no gene flow between populations; |
| d | temporal isolation if two populations breed at different times/valid example; |
| e | behavioral isolation if breeding prevented by differences in behaviour/valid example; |
| f | geographical isolation if populations live in different areas / are separated by a physical barrier/valid example; |
| g | differences in mutations/genetic drift between isolated populations; |
| h | differences between environments cause different selection pressures/natural selection; |
| i | allele frequencies of isolated populations diverge; |
| j | evolutionary divergence/different evolutionary paths/different adaptation; |
| k | populations have become separate species when they are too different for successful interbreeding/for interbreeding to produce fertile offspring OR polyploidy can cause (instant) reproductive isolation; |